-

,­
Coiled-Tubing Stress Analysis Model
Stress/Drag/Hydraulic/Buckling
(CSTRESSl)

Theory and User's Manual

By

MAURER ENGINEERING INC.

2916 West. T.C. Jester Boulevard
Houston, TX 77018-7098

Telephone: 713/683-8227 Telex: 216556

Facsimile: 713/683-6418

August 1993
TR93-11

This copyrighted 1993 confidential report and the computer prognm are for the sole use
of Participants on the Drilling Engineering Association DEA-67 project to DEVELOP
AND EVALUATE SLIM-HOLE AND COILED-TUBING TECHNOLOGY and their
affiliates, and are not to be disclosed to other parties. Data output from this program
can be disclosed to third parties. Participants and their affiliates are free to make copies
of this report and programs for their own use.
- Table of Contents

Page
1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1 Model Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.1.1 General Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-l
1.1.2 Drag Force, Axial Load, and Triaxial Stress . . . . . . . . . . . . . . . 1-1
1.1.3 Hydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.1.4 Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.1.5 Tortuosity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2 COPYRIGHT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.3 DISCLAIMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

2. THEORY AND EQUATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.1 AXIAL DRAG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1.1 Introduction to the Variables . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.1.2 Derivation of the Equations . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.1.3 Consideration of Multi-Element Cases . . . . . . . . . . . . . . . . . . . 2-2

2.2 APPLYING THE DRAG MODEL TO A STRING OF COILED TUBING 2-3

2.2.1 Physical Size and Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.2.2 Spatial Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.2.3 Nature of Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.2.4 Loads at the Bottom of Each Element . . . . . . . . . . . . . . . . . . . 2-3
2.2.5 Loads at the Top of the Coiled Tubing . . . . . . . . . . . . . . . . . . . 2-4
2.2.6 Friction Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.2.7 Cable Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.3 AXIAL STRESS AND LOAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.3.1 Load at Bottom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.3.2 Axial Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.3.3 Hook Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.3.4 Axial Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.3.5 Axial Load and Axial Drag . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2.4 BENDING STRESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2.5 HYDRAULICS ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2.5.1 Bingham Plastic Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2.5.2 Power-Law Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
2.5.3 Bit Pressure Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14
2.5.4 Equivalent Circulating Density . . . . . . . . . . . . . . . . . . . . . . . 2-16

iii
 Table of Contents (Cont'd.)

2.6 SURGE AND SWAB PRESSURES . . . . . . . . . . . . . . . . . . . . . . . . 2-16

2.7 BUCKLING THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
2.7.1 Sinusoidal Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
2. 7 .2 Helical Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18
2.7.3 Spring Theory Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
2.7.4 Which One Do I Use? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21
2.8 HELICAL FRICTIONAL FORCE AND LOCKUP . . . . . . . . . . . . . . 2-21
2.9 TRIAXIAL, BIAXIAL, AND API STRESS ANALYSIS . . . . . . . . . . . 2-22
2.9.1 Triaxial Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23
2.9.2 Biaxial Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
2.9.3 API Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25

3. TORTUOSITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1 MODEL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

4. PROGRAM INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

4.1 BEFORE INSTALUNG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.1.1 Check the Hardware and System Requirements . . . . . . . . . . . . . . 4-1
4.1.2 Check the Program Disk . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.1.3 Backup Disk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.2 INSTALUNG CSTRESSl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.3 STARTING CSTRESSl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4.3.1 Start CSTRESSl from Group Window . . . . . . . . . . . . . . . . . . . 4-3
4.3.2 Use Command-Line Option from Windows . . . . . . . . . . . . . . . . 4-3

4.4 ALTERNATIVE SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

5. BASIC OPERATION OF MICROSOFT WINDOWS . . . . . . . . . . . . . . . . 5-1

5.1 THE TITLE BAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.2 THE CONTROL BOXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.3 MINIMIZE AND MAXIMIZE BOXES . . . . . . . . . . . . . . . . . . . . . . 5-1
5.4 TEXT BOXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.5 CHECK BOXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.6 OPTION BUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.7 COMMAND BUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

iv
 - Table of Contents (Cont'd.)

Page
5.8 LIST BOXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.9 DROP-DOWN UST BOXES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5.10 SCROLL BARS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5.11 GRID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

6. RUNNING CSTRESSl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.1 OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2 GETTING STARTED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
6.3 PULL-DOWN MENUS IN THE INPUT WINDOW . . . . . . . . . . . . . . 6-3
6.4 THE INPUT WINDOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8
6.4.1 Page 1: Criteria Window . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8
6.4.2 Page 2: Well Data Input (WDI) . . . . . . . . . . . . . . . . . . . . . . . 6-9
6.4.3 Page 3: Survey Data Input (SDI) . . . . . . . . . . . . . . . . . . . . . . 6-9
6.4.4 Page 4: Tubular Data Input (TOI) . . . . . . . . . . . . . . . . . . . . 6-10

- - 6.5
6.6
6.7
6.4.5 Page 5: Parameter Data Input (POI) . . . . . . . . . . . . . . . . . . . 6-13
SAVE INDIVIDUAL FILES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
RUN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15
OUTPUT WINDOW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15
6.7.1 Print Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16
6.7.2 Manipulating the Output Graph . . . . . . . . . . . . . . . . . . . . . . 6-17
6.7.3 Select Output Graph Curves . . . . . . . . . . . . . . . . . . . . . . . . 6-19
6.7.4 Bi-Axial Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20
6.7.5 Pump Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
6.7.6 Exit Output Window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21
6.8 USING TORTUOSITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22
6.9 CSTRESS HELP AND DIALOG BOXES . . . . . . . . . . . . . . . . . . . . 6-23
6.9.1 Help - Assistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23
6.9.2 Help - About... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24
6.9.3 Open Project and Data File . . . . . . . . . . . . . . . . . . . . . . . . . 6-24
6.9.4 Save Project - Data File . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26
6.9.5 Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26
6.10 CSTRESS ERROR HANDLING . . . . . . . . . . . . . . . . . . . . . . . . . . 6-27
6.11 QUICK START . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-27

7. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

8. BUG REPORT OR ENHANCEMENT SUGGESTION FORM . . . . . . . . . . 8-1

v
vi
.­ 1. Introduction

The coiled-tubing stress analysis (coiled-tubing stress/drag/hydraulic/buckling) windows applications

program (CSTRESSl) has been developed by Maurer Engineering Inc. as part of the DEA-67 project
to "Develop and Evaluate Slim-Hole and Coiled-Tubing Technology." This program, coded in Visual
Basic 1.0, is written for use with IBM or IBM compatible computers and must run with Microsoft
Windows 3.0 or later version.

1.1 MODEL DESCRIPTION

CSTRESSl is an integrated computer program of drag force, hydraulics, buckling, and triaxial
stress analysis. It is a major rewrite of the coiled-tubing model, not just an update. The features of
CSTRESSl are listed below.

1.1.1 General Features

1. MS Windows applications.
2. Five operations: pick up (logging), slack off (logging), pick up (drilling - tripping),
slack off (drilling - tripping), and drill.
3. Supports both color and monochrome monitors.

- 4. Supports English and metric unit systems.

5. Handles up to fifteen tube segments and twenty well intervals.
6. Coiled-tubing and casing data can be imported from the built-in data base file directly.
7. Enables the user to modify the data base within the program.
8. Allows input of pore and fracture pressures for different well interval.
9. Results, data and graphs, can be output to screen, printer, and disk file.
10. Selectable curves on output graphic presentation.

1.1.2 Drag Force. Axial Load. and Triaxial Stress

1. Computes axial drag on coiled-tubing during pick up, slack off, and drilling.
2. Computes axial load and stress on coiled-tubing during pick up, slack off, and drilling.
The axial load and stress is based on tubing pressure, annulus pressure, pipe weight,
and frictional force.
3. Bending stress (based on dogleg or helical buckling curvature) can be included in the
calculation.
4. Extra frictional force caused by helical buckling can be included in the calculation.
5. Calculates triaxial stress and has both graphics and text output.
6. Calculates allowable working stress and pressure for biaxial and API stress criteria
with graphic output.
7. Calculates maximum cable load.

1-1
 1.1.3 Hydraulics
I. Calculates internal and external pressures on the tubing at various locations during
tripping and drilling.
2. Calculates bottom-hole pressure and ECD during tripping.
3. Calculates ECD corresponding to the total pressure along the wellbore.
4. Plots pore and fracture pressures along the wellbore (optional).
5. Calculates pressure loss of the coiled tubing remaining on the reel.
6. Calculates the required pump horsepower.

1.1.4 Buckling
I. For compressive loads, the onset of I) sinusoidal buckling, 2) helical buckling, and 3)
limiting yield stress are indicated.
2. Two sinusoidal buckling criteria can be evaluated: 1) Exxon's equation, and 2) Texas
A&M University's equation.
3. Two helical buckling criteria can be evaluated: I) Rice University's equation, and 2)
Texas A&M University's equation.

1.1.5 Tortuosity
I. Survey data can be "tortured" (add tortuosity along the trajectory of wellpath).
2. Allows insertion of equally spaced stations to survey data.
3. Different tortuosity amplitude and cycle lengths can be applied up to five wellpath
intervals.

1.2 COPYRIGHT

Participants in DEA-67 can provide data output from this copyrighted program to third parties and
can duplicate the program and manual for their in-house use, but will not give copies of the program or
manual to third parties.

1.3 DISCLAIMER

No warranty or representation is expressed or implied, with respect to these programs or

documentation, including their quality. performance, merchantability. or fitness for a particular purpose.

1-2
- 2. Theory and Equations

2.1 AXIAL DRAG

The drag model is based on a simple mathematical model, developed by Exxon Production
Research (Johancsik et al., 1984). The model assumes the loads on the tubing result solely from effects
of gravity and frictional drag resulting from contact of the tubing with the wall of the hole. These
frictional forces are the products of the normal force acting between the tubing and the wellbore and the
coefficient of friction (friction factor). Two contributions to the normal force are considered for this
model: l) the effects of gravity on the tubing and 2) the effects of tension and compression acting
through curvatures in the wellbore. Although bending may make minor contributions to normal force,
its effect is neglected in this model.

The model considers the tubing to be made up of short segments joined by connections which
transmit tension, compression and torsion, but not bending moment. The basic equations of friction are
applied to each segment with the calculations starting at the bottom of the tubing and proceeding upward
to the surface. Each short element thus contributes small increments of axial drag and weight. These
forces are summed to produce the total loads on the tubing. For this version of CSTRESS, torsion is
- not taken into consideration.

2.1.1 Introduction to the Variables

Figure 2-1 is a simple free-body diagram of a single element of the tubing.

Figure 2-1. Free-Body Diagram of a Single Element

2-1
where:
f = Friction Factor
F = Axial Friction Force
M Torque = 0 for Coiled Tubing
N = Normal Force
T Tension
R = Effective Radius of Element
WTM Buoyancy Weight of Coiled Tubing or Weight in Mud

WcM Buoyancy Weight of Loose Cable in Coiled Tubing

8 = Inclination Angle
7J = Average Inclination Angle
= Azimuth Angle
"'
.6. Incremental Values

2.1.2 Derivation or the Equations

When a loose cable is suspended inside the coiled tubing, the weight of the cable is
suspended by the reel while the weight of the tubing and frictional drag are suspended by the injector
head (hook load). Therefore, the weight of the cable effects the weight term in the normal force equation
(Eq. 2-1), but does not effect the weight term in the tension increment equation (Eq. 2-2).

In analyzing each segment, the first requirement is to calculate the magnitude of the
normal force, N, as follows:

(2-1)

The tension increment is then calculated as follows:

.6.T " WTM cos7J ± F (2-2)

F "fN (2-3)
(2-4)
or .6.T " WTM cos7J ± fN

In this equation, the plus sign is used for upward motion (meaning axial drag adds to the effect
of gravity), and the minus for downward motion (meaning axial drag subtracts from the effect of gravity).

2.1.3 Consideration or Multi-Element Cases

As the calculation procedure takes place, T + .6.T becomes T for the element above the
present calculation point and .6.T contributes to the overall sum. When completed, the analysis yields
tensile loads as functions of depth along the string.

2-2
-
- 2.2 APPLYING THE DRAG MODEL TO A STRING OF COILED TUBING

To apply the mathematical model in the stepwise fashion as shown earlier, it is necessary to
specify the following information for each element:

1. Physical size and weight

2. Spatial orientation
3. Nature of motion
4. Tensile load at the bottom of the element
5. Friction factor

The following paragraphs discuss each of these and relate them to tubing design or operational
parameters, whichever is applicable.

2.2.1 Physical Size and Weight

One aspect of physical size is the length of the element. When a stepwise solution is
applied, this will be the size of each "step" as the solution process marches up the tubing. The outside
and inside diameters of the elements are needed to calculate stress and buckling criteria. These are
obtained from a physical description of the tubing. The weight of the element, adjusted for the effects
of buoyancy, is part of the tensile force balance.

2.2.2 Spatial Orientation

- Spatial orientation refers to the values for inclination and azimuth angle at both ends of
the element. These can be obtained from weHbore survey information.

2.2.3 Nature or Motion

The nature of the motion is necessary to determine what effect the drag force has. If the
string is moving up, the drag force adds to the weight component of tension. When downward motion
is present, the drag force subtracts from the weight component.

In terms of actual operations, upward motion occurs when raising the string of tubing
(i.e., picking up or coming out of the hole). Downward motion corresponds to lowering the string (i.e.,
slacking off, drilling, or going in the hole).

2.2.4 Loads at the Bottom or Each Element

The tensile drag at the lower end of the element must be known prior to calculation of
the element. Remember, the model takes the increment of tension due to drag and weight and adds this
to the tension value found at the lower end of the element. However, this information does not have to
be supplied for every element because the model uses the value calculated for the upper end of the
current element as the initial value for the lower end of the next element. Thus, the boundary conditions
of the tensile drag at the bottom of the string are all that must be provided.

2-3
 The values used for boundary conditions at the bottom of the coiled-tubing string will
depend upon the operation being simulated. When the string is going into the hole, (slack off or drill),
the bottom of the string is in compression. When the string is coming out of the hole, the bottom of the
string is in tension. The following are the factors that affect bottom boundary conditions for each
operation being simulated.
1. Pick up (logging): Consists of logging tool weight and bottom tool drag.
2. Slack off (logging): Consists of logging tool weight and bottom tool drag.
3. Pick up (drilling, tripping): Consists of bottom tool drag.
4. Slack off (drilling, tripping): Consists of bottom tool drag.
5. Drill: Consists of bottom tool drag and weight-on-bit.

2.2.5 Loads at the Too or the Coiled Tubing

Stuffing box drag is a load applied both during pick up and slack off. It simulates the
frictional drag in the seal of a stuffing box or lubricator. It has no effect on the tension loading of the
tubing below the stuffing box. It increases tension in the tubing above the stuffing box during pick up
operations and decreases tension when slacking off.

Coiled-tubing reels keep a constant back tension on coiled-tubing which is called pick-up
reel back tension and slack-off reel back tension. This back tension reduces the load read on the
transducers at the injection head. The back tension is always in the same direction, whereas friction in
the stuffing box gland changes direction from pick up to slack off.

2.2.6 Friction Factor

The friction factor is a very important number because it is the one parameter that char­
acterizes the surface-to-surface interaction central to the mathematical model. A great amount of work
has gone into obtaining and verifying values of friction factor for predictive work. A few comments at
this point will facilitate a better understanding of the application of friction factors to coiled tubing. The
exact value of the friction factor applicable to a situation is a function of many things, including drilling
fluid type and composition, formation type (in open hole), casing material and condition (in cased hole),
and tubing material and condition (e.g., roughness). At a single point in time, the mud type and
composition in the well are constant but significant changes may be taking place in portions of both cased
and open hole. Thus, in certain cases, it may be necessary to use two friction factors, one for the
tubing/casing interaction and one for the tubing/formation interaction.

2.2.7 Cable Load

The maximum tensile cable load, Tc, at the top of the cable equals:

Tc TVDcable X Wc (2-5)
where:
Tc Maximum Cable Tensile Load
TVDcable Maximum TVD of Cable
WC Cable Buoyed Weight

This tensile load is supported by the reel and not by the injector head.

2-4
 - 2.3 AXIAL STRESS AND LOAD

The torque and drag model mentioned previously considers only the effects of mechanical force
or drag force. It does not consider compressive loads imposed on the tubing string as a result of
hydrostatic pressure. The model gives correct results for torque and drag and buckling calculations but
not for mechanical strength failures an:! burst an:! collapse estimales. Therefore, load contribution due to
hydraulic pressure must be coffiidered.

2.3.1 Load at Bottom

A hydrostatic or buoyant compressive force acts on the bottom of the tube. This force
is caused by the hydrostatic pressure in the liquid at the bottom of the hole. The magnitude of this force
is given by

Fhb = - ?r ( Pob x OD 2- Pib x ID 2) (2-6)

4

Fhb Compressive load acting on the end of the tubing string

Pob = Bottom tube annual pressure
Pib Bottom tube inside pressure
OD Bottom tube outside diameter

- ID Bottom tube inside diameter

When hydraulic force combines with logging tool weight, BHA drag, or weight-on-bit
it becomes bottom-boundary load.

2.3.2 Axial Load

To calculate axial load, you would modify Eqs. 2-2 to 2-4. Since hydrostatic pressure
is considered in the bottom-boundary load, the buoyancy force should not affect pipe weight contribution
in the axial direction. For normal force (lateral side load), buoyancy must be considered. In analyzing
each segment, Eqs. 2-I to 2-4 become:

(2-7)
-
It is the same as Eq. 2- I, the tension increment is calculated as follows:

1>Ta=WT • cos1J±F (2-8)

a

F = f N or (2-9)

"'Ta = WT • cos 1J ± f N (2-IO)

"

2-5
where:
A Ta Axial load (tension) increment
WTa = Tubing weight in air
N = Normal force
f = Friction factor
F Axial friction force

2.3.3 Hook Load

Hook load measured at the injector head equals:

Hook Load (Pick up) = Tp + F0 - FR

Hook Load (Slack oft) = Ts - F 0 - FR
Hook Load (Drill) = TD - Fo - FR
where:
Tp = Pick-up Tensile Tubing Load below Stuffing Box
Ts Slack-off Tensile Tubing Load below Stuffing Box
To = Drill Tensile Tubing Load below Stuffing Box
Fo = Stuffing Box Drag
FR = Reel Back Tension

This hook load is applied to the tubing by the injector head. The hook load does not
include the force to support the cable since the cable is supported by the reel and not by the injector head.

2.3.4 Axial Stress

Axial stress without bending stress which is exerted by wellbore dogleg or helical
buckling is:

O'a = Ta I cross section area or (2-11)

(2-12)

where:
ua = Axial stress

Ta = Axial load

2-6
..,
I

- 2.3.5 Axial Load and Axial Drag

FORCE 0

. ID AXIAL LOAD
(USE WBGHT IN AIR
TO CALCULATE)
OD-. ~
AXIAL DRAG
(USE BUOYNACY WEIGHT
Pib TO CALCULATE)
......
Pob

HYDRAULIC /::TICAL DEPTH

PRES SU RE ACT AT
BOTIOM

Figure 2-2. Compare Axial Load and Axial Drag

Shown in Figure 2-2 is a steel tube in water. At the bottom of the tube, the inside and
outside pressures are equal. Axial load curve and axial drag curve that intersect at water level can easily
be found. For axial drag calcuJation, tube buoyancy weight (weight in water) is used. For calcuJating
axial load, weight in air and hydraulic pressure at the bottom of the tube are used.

2.4 BENDING STRESS

Bending stress can be exerted by either wellbore dogleg or helical buckling. The bending stress
from dogleg is shown below:

uDL = ('ll' • E • DL • OD) /432000 (2-13)

where:
uDL Bending stress exerted by dogleg (psi)
E = Elastic modulus (psi)
DL = Dogleg ( 0 /HJO ft)
OD Tube outside diameter (in.)

If the tubing is in helical bending, the path of tubing is not only following the wellbore, but is
also following the spiral shape (Lubinski et al., "Helical Buckling of Tubing Sealed in Packer" Journal
ofPetroleum Technology, June, 1992). The pitch of helical buckling can be estimated due to axial drag.
After the pitch is obtained, the curvature of the tube with helical buckling can be found.
r Clearance
P Pitch of helical buckling
k = Curvature of the tube with helical buckling
uhel Bending stress due to helical buckling

2-7
 E = Elastic mcxlulus
I = Moment of inertia
HID = Hole diameter
T Axial drag
OD = Tube outside diameter

(2-14)
p"'

HID - OD (2-15)
r "'
2

4~r (2-16)
k"'----­
p2 + 4~82

E • k • OD (2-17)
2

uhel is the helically buckled tube's bending stress, so in the helical buckling section of coiled
tubing, the bending stress will be uhel (Eq. 2-17) rather than unL (Eq. 2-13).

2.5 HYDRAULICS ANALYSIS

The mcxlels most commonly used in the drilling industry to describe fluid behavior are the
Bingham plastic and power-law mcxlels. They can be used to calculate frictional pressure drop, swab
and surge pressures, etc. The hydraulic calculation in CSTRESS 1 is based on equations derived in
Applied Drilling Engineering (Bourgoyne et al., 1986) and API SPEC 10. The more sophisticated
Herschel-Buckley mcxlel has not been included in this program because of lack of experimental data, but
it will be considered in the future version.

2.5.1 Bingham Plastic Model

The Bingham plastic mcxlel is defined by Eq. 2-18 and is illustrated in Figure 2-3.

(2-18)

2-8
-
where:
ry = Yield stress
l'-p Fluid viscosity
r = Shear stress
i' Shear rate

0
·>-­"

I SHEAR RATE' y

~-~
Figure 2-3. Shear Stress Vs. Shear Rate for a Bingham Plastic Fluid
(Bourgoyne et al., 1986)

As shown in Figure 2-3, a threshold shear stress known as the yield point (ry) must be
exceeded before mud movement is initiated.

The mud properties l'-p and "Y are calculated from 300- and 600-rpm readings of the
viscometer as follows:
=
(2-19)

where:
8600 , 8300 = shear readings at 600 and 300 rpm, respectively.

Calculation of frictional pressure drop for a pipe or annulus requires knowledge of the
mud flow regime (laminar or turbulent).

1. Mean Velocity
The mean velocities of fluid are calculated by Eq. 2-20 and 2-21.
For pipe flow:
v
Q
= ----=- (2-20)
2.448d2

2-9
 For annular flow:
Q
v = -----­
<li _dn
(2-21)
2.448 (

Where:
v = Mean velocity, ftfsec
Q Aow rate, gal/min
d = Pipe diameter, in.
d1 = Casing or hole ID, in.
d1 = Drill string OD, in.

2. Hedstrom Number
The Hedstrom number, NHE, is a dimensionless parameter used for fluid flow regime
prediction.
For pipe flow:

NHE = (2-22)

For annular flow:

24,7()() p Ty (d2 - di)2
(2-23)
2
J.Lp

Where:
p = Mud weight, lb/gal

3. Critical Reynolds Number

The critical Reynolds number marks the transition from laminar flow to turbulent
flow. The correlation between Hedstrom number and critical Reynolds number is presented in
Figure 2-4. The data in Figure 2-4 have been digitized in the program for easy access.

2-10
.... ,i '' . '

••
·I I•
' " ' ' ''I'
. 'I 1
' '.' '
'' • I\ I
I I I I ~ I I I I I I I!\ , ,' I ! l 111 : I I I j I I
u
' ' ' ' '
0: I I ·I I 1 11 i' I i I I I 1111 I I I i 1111: I i I I iJ-.t
z 3

a: 2
'1 ''I I 11 l I\ 1, I ! I
'
! 11111 I
I I I ! ! 1111 I _)--("\ I 111
I

I~
LU

"'
::
~ 10 4 '
I I
I
! !i 1111
I
! I II 11111
1

1 I I I I I I I I ' II\
I : ! I
1
1

-. II>
0
i7
.
.
~

. . ''

••
;
''
...J ' ' i I; ; 111 I'': I
~ : I I
0 I
'
,.
z
•
'
I
'·

! i l I
I
! I II
I IJ.J,....--" ''
'~ : I : I: I i I II I I I
' ! I t I I

"'a: 3
I I I i
' i
' i I II I 1 I I I I Ii I; i I i ! I I 11 I
...J
<
u 2
I
I I 111 II I ! I I I 11 I I I I
I I 111
1

1 I ! I I I I
' 111
;:::
~
u 103 I
I

I 1, 11 11
I
I
I
I
I 111 iII I
I
I 1111111 I I i I '1
1

1
1

1 I
•e' ''' ''I
'•
' ' '
'

~
I

6 i
I''

8~ I

' ' . ~67@91

''
10"' ' ' "° ~
'I

6 7 S:i
I 1 I

I
' ' .. ~t7!9
' 1 I

··~ HEDSTROM NUMBER, N,..,

Figure 2-4. Critical Reynolds Numbers for Bingham Plastic Fluids

(Bourgoyne et al., 1986)

- 4. Reynolds Number
Reynolds number, NRe• is another common dimensionless fluid flow parameter.
For pipe flow:
928pvd (2-24)
NRe =--­
1'-p
For annular flow:
757 p v (d2 - d1)
NRe = - - - - - ­ (2-25)
·­ 1'-p
5. Frictional Pressure Drop Calculation
For pipe flow, the frictional pressure drop is given by:
(1) Laminar flow (NRe < Critical NRe)
+ _Ty
_
(2-26)
225d

(2) Turbulent flow (NRe ~ Critical NRe )

dPr _ fpv 2 (2-27)

dL - 25.Sd
where f is the friction factor given by

2-11
 Jl = 4 log (NRelf) - 0.395 (2-28)

For annular flow, the frictional pressure drop is:

(1) Laminar flow (NRe < Critical NRe )

dPf = P-pV + Ty
dL -1000~-(-d2___d_1~)2 ~~~- (2-29)
200 (d2 - di)

(2) Turbulent flow (NRe ~ Critical NRe )

dPr _ fpv2
(2-30)
dL - 21.1 (d2 -di)
where f is determined using Eq. 2-28.

2.5.2 Power-Law Model

The power-law model is defined by Eq. 2-31 and illustrated in Figure 2-5.
(2-31)

where:
K = Consistency index, equivalent centipoise (see Bourgoyne et al., 1986)
n = Flow behavior index, dimensionless

SHEAR RATE, "f

= Ky Iti
n- I
T

Figure 2-5. Shear Stress Vs. Shear Rate for a Power-Law Fluid (Bourgoyne et al., 1986)

The fluid properties n and K are calculated as follows:

2-12
1
f}r,oo (2-32)
n = 3.32 log-­
6300

K = 510 6300 (2-33)

511"
The critical Reynolds number must be determined before the frictional pressure drop
can be calculated.
1. Mean Velocity
For pipe flow:

v = __Q..;:_~ (2-34)
2.448d 2
For annular flow:
v = _ ___;:Q::...__....,.
(2-35)
2.448 (di _ dn

2. Critical Reynolds Number

The critical Reynolds number can be read from Figure 2-6 for a given flow
behavior index n.

.­ o..
Ii
I~
·­

:
,.
.'-
•
~ I
i'.. : I I I I\
1
... ,
i I\'
:
'
I I
I

ii 111!
It
.
I
"
I,
.

I
I

I 1 1111!
.. '
I I • I'
I
'
I I
''
i i; 11
'!!

i I:~"I ii 111! I i 111

I
1: ! I 11 I I '1
I I I I Ii 11 Ii I I I

o.a I:
I i i I I'!\~ ~ I I IIII '1 I
I
I I ! Ii 111,1 I .I I II\I.II

il
!''• ', ..,, ~

-
--- ''I·
~ ~
,; ' ''.
: I\; I
----
• 1 --......_. I : '

~ I' : ·~1111 ~ , ~ ' I ,-;---_,,_: ~,..·,_c~

1: I
'

I I i I I\\:
: ' J

I
I

! I I),.U \i'--.. i 1~11~6~

~ 1l"i"T
0.00
I',
,
\
'
I I Ii 1111 !
I

I 1111 \lt', I
I
I
·. 'I Ill
I
I'I 111·:s.-_ I
I
1·0-:..Ll
I 111 i!
,; O•-­

.•',. t

I•. 11!:
I:']

I
'
I
.'
\
1
,
''
•

1111
,,
t •• ,. 1 I I 'I'
1"' ...( j \ I ~ l
' i
•

I
'.
'I

I' Ii
!II

-'~!r""-'">.:ll-'-1_ _.. .:.:_ 1.:...':...:..:I

i I I I I ' ' I
I •--,--1---,--'-'-'1-'-l-;.-I'-'"11_·--'-'_.:_1_1_1:....;'....:.I-'-!-'-!--'-'--""' I ']·

=
! I i ! ! II
1 i, I I \I III 1
~'-:----'-'-'-'-'"'-'-'...:.'.;..;'' --'-' --'--'----'-'-'''-'''-'''-''-"'"C:..'--'--'---'''-'"'-'·''-'"'.!..:"::...'-'.>.....!'--2.-'!.2...'!..!..:",.' '"
11 IInt, I ', I! 111
>JV 1000 :COOO 100000 1000.o:x>

Figure 2-6. Friction Factors for Power-Law Fluid Model (Bourgoyne et al., 1986)

The data in Figure 2-6 can be approximated by the following (Leitao et al., 1990):
Critical NRe = 4200 for n < 0.2
Critical NRe = 5960 - 8800 n for 0.2 ~ n ~ 0.45 (2-36)
Critical NRe = 2000 for n > 0.45

2-13
 3. Reynolds Number
For pipe flow:

89,lOOp v <2 -n) [ 0.0416 d] 0

(2-37)
NRe = K 3 + l/n

For annular flow:

N = 109 ,OOOp V(2-n) [ 0.0208 (d2 - d1)] n (2-38)

Re K 2 + l/n

4. Frictional Pressure Drop Calculation

For pipe flow:
(1) Laminar flow: (NRe < Critical NRJ
0
dPf Kv [ 3 + l/n]
0
(2-39)
dL = 144,000 d (1 +n) 0.0416

(2) Turbulent flow (NRe ~ Critical NRJ

dPr _ fpv 2 (2-40)
dL - 25.8d
where the frictional factor f is given by:

ff _ 4.0 I (N f(l-n/2)) _ 0.395

- - - o g Re
n0.75
-­
nl.2
(2-41)

For annular flow:

(1) Laminar flow: (NRe < Critical NRJ
0
dPr Kv [2 + l/n]
0
(2-42)
dL = 144,000 (d - di)'l+n) 0.0208
2

(2) Turbulent flow (NRe ~ Critical NRJ

dPr fpv 2 (2-43)

dL 21.1 (d2 -di)
where f is calculated using Eq. 2-41.

2.5.3 Bit Pressure Drop

There are three assumptions made to calculate bit pressure drop:
I. The change in pressure due to change in elevation is negligible.

2-14
1
2. Upstream velocity is negligible compared to nozzle velocity.
3. Frictional pressure drop across the nozzle is negligible.
1 Nozzle velocity equals
Q
vn =.,,......,~-
3.117 AT
(2-44)

where:
Vn = Nozzle velocity, ft/sec
Q = Flow rate, gal/min
AT = Total nozzle area, in. 2
and bit pressure drop equals

(2-45)

where:
Cd = discharge coefficient factor (recommended value = 0.95)
(Bourgoyne et al., 1986)

- The hydraulic horsepower (HHP) and the impact force (F;) at the bit are

HHP = dPbQ
1714
(2-46)

(2-47)

The total pressure drop in the system equals:

Ptotal =E Pp+ E Pa+ dPb (2-48)

Where:
E PP = Summation of pressure losses inside the pipe
E Pa = Summation of pressure losses in the annulus
Therefore, the pump horsepower (PHP) is

PHP = Ptotal _g_ (2-49)

1714

where:

·-- surface equipment pressure loss, psi

flow rate, gal/min

2-15
 2.S.4 EauivaJent Circulating Density
Of particular importance is the equivalent circulating density (ECD) at a certain depth. The
ECD is the density of fluid that will produce the same hydrostatic pressure as the circulating presmire
at that point (bottom of the hole) i.e.,
p0
ECD = (lb/gal) (2-50)
0.052 x TVD

where:
P0 = Pressure at the point, psi
TVD True vertical depth at the point, ft

2.6 SURGE AND SWAB PRESSURES

Equations 2-26 through 2-30 and 2-39 through 2-43 have been presented for frictional pressure
drop calculation, the first set for a Bingham plastic fluid and the second for a power-law fluid. These
models can also be applied to determine surge and swab pressures if the running speed of the drill pipe
is known. Surge pressure is the pressure increase caused by lowering pipe into the well. Pressure
decrease, resulting from withdrawing pipe from the well, is called swab pressure.

For a closed pipe, the estimated annular velocity is (Moore, 1974):

v = (2-51)

where:
vp Pipe running speed, ft/min
v Average annular fluid velocity, ft/min
K = Clinging constant (recommended value = 0.45).

Moore suggested using maximum fluid velocity to take into account the acceleration and
deceleration of the pipe. In general, the maximum fluid velocity equals:
vm = 1.5v (2-52)

Surge and swab pressures are calculated by substituting maximum fluid velocity for mean velocity
in the previously presented frictional pressure drop equations.

Of particular importance is the equivalent circulating density (ECD) due to surge and swab
pressures. The calculation of ECD can be performed using Eq. 2-50.

2-16
1
1- 2.7 BUCKLING THEORY
., The compressive loads required to initiate the onset of sinusoidal, helical, and spring 1heory
I
buckling are indicated on the graphic output of the slack-off plots. The significance of these three stages
of buckling is as follows:

2.7.1 Sinusoidal Buckling

As compressive force is increased on a length of tubing lying along the bottom of an
inclined hole, a point is reached where the tubing will assume a sinusoidal configuration along the bottom
of the hole (Figure 2-7). The critical force required to achieve this is calculated using either the Exxon
formula presented in Eq. 2-53 (Dawson and Paslay, Jourrwl Petroleum Technology, October 1984, 1734
- 1738) or the Texas A&M University formula presented in Eqs. 2-55 - 2-57 (Wu and Juvkam-Wold,
ASME Paper 93-PET-7).

where:
Fcsin Critical axial load to begin sinusoidal buckling, lbf
E Elastic modulus, psi
I = Moment of inertia of tubing cross section, inches4
r = Radial clearance between tubing and borehole, inches
6 = Inclination of hole, degrees
1J = Average inclination of hole section, degree
wmud = Unit pipe weight in mud, !bf/in.
R = Radius of the curvature, in.

In Exxon's equation, if the inclination angle is zero, then the sinusoidal buckling critical
load is zero. In the program CSTRESS, if the inclination is less than 3°, the program uses 3° instead
of the inclination (Eq. 2-54).

Exxon
112
E • I•Wmrud ·Sin (9) ] (2-53)
Fcsin = 2 [ (for 6 >3°)

Exxon
1/2
_ E • I• W mud •Sin (3) (2-54)
Fcsin - 2 [ (for 6 <" 3°}
r
l
For the vertical, slant, and curved sections, A&M uses three equations for each situation
to find the critical buckling load.

2-17
 A&M

(
Fein= 0.85 E •I• Wmud 2 )1'3 ( for vertical)
(2-55)

A&M
12
[ E • I • W ~ud • sin (IJ)] 1 (2-56)
Fcsin = 2 • (for slant)

A&M

Fcsin =
4 • E •I
r •k
[I• [I• "R'·~;~·••(Uf'] (for curved)
(2-57)

18000 x 12
R =
DL
'll' • (2-58)

Figure 2-7. Sinusoidal Buckling

2.7.2 Helical Buckling

If the axial compressive load is increased beyond the point where sinusoidal buckling
occurs, helical buckling will eventually result. In helical buckling, the tubing forms a helix along the
wall of the hole, the pitch of the helix decreasing as compressive load increases (Figure 2-8).

2-18
 -

Figure 2-8. Helical Buckling

- - The critical force required to achieve helical buckling is calculated using either the Rice
University formula presented in Eq. 2-59 (Chen, Lin, and Cheatham, 1989, "An Analysis of Tubing and
Casing Buckling in Horiwntal Wells," OTC 6037) or the Texas A&M University formula presented in
Eqs. 2-61 - 2-63 (Wu and Juvkam-Wold, ASME Paper 93-PET-7).

Rice
112
E · I · Wmrud • sin(U)] (2-59)
Fchel = 2 •.fl • [
(for () > 3°)

Rice
112
r:;- [ E • I • Wmud •sin (3) ) (2-60)
Fhl
c e =2•y,;..
(for () < = 3°)
- A&M
r

2 )1/3 (2-61)
Fchel = 2.85 ( E •I. Wmud ( for vertical)

A&M
In
Fchel = 2 (2 • .ff - 1)
[
E ·I · W
~ud • sin
(U)
]
(for slant)
(2-62)

2-19
 A&M
2
12 • E • I 4 •__
+ _ E • I r • R 2 • W mud • sin (11)] 11
Fchel
r •R r•R [4 • [ l + -----=-=-c---­
8 EI
(2-63)

112]
l
2
+ r·R ·Wmud·sin(1J)
4 • E ·I

From Exxon's and Rice's formulas (Eqs. 2-53 and 2-59), helical buckling begins when the
axial compressive force is l.414 (/f) times the value of sinusoidal critical buckling load.

2.7.3 Suring Theory Buckling

If compressive axial load is increased beyond that required to initiate helical buckling, the
pitch of the helix decreases until a point is reached where the shear stress loading of the tubing will equal
its minimum yield shear stress (Figure 2-9). This is calculated using Equation 2-64 which is based on
the theory of helical springs under compression. (See A.M. Wahl, "Mecha.nical Springs," 2nd edition,
McGraw Hill Book Company, New York, 1963.)

'll'd 2 t
(2-64)

where:
Fcspr = Critical force required 1o ~ maximum shear 1o equal minimum yield shear, lbs
d = Tubing diameter, inches
D = Hole diameter, inches
Minimum yield in shear, psi. This is equal to half of the tensile yield.

(a)

(a) AJ:i.aUy loaded helical spring; (b) free-body d'3gum showing that the wire ;,
su bjcctcd to a. direct shc.21" a.nd a. ton:ional ihar.

Figure 2-9. Axially-Loaded Helical Spring

2-20
 2.7.4 Which One Do I Use?
- As indicated above, the smallest critical force is Pesin• the critical compressive force
required to initiate sinusoidal buckling. Next largest is F chel• the critical compressive force to change
from sinusoidal to helical buckling. The largest of the three critical forces is F cspr• the axial force
required to increase the maximum shear in the coiled tubing to equal the minimum yield in shear of the
tubing.

Newman, Corrigan, and Cheatham, in SPE 19229, indicate that coiled tubing can be pushed
into a hole safely using compressive loads considerably in excess of the sinusoidal buckling threshold
calculated by Equations 2-53 - 2-57. In the field cases they report, compressive forces greater than the
sinusoidal critical force, F csin• have been used to push coiled tubing into inclined holes. Because of well
geometry, they were unable to test compressive forces greater than the helical buckling critical force,
Fchel. It is their belief that compressive forces larger than the critical helical buckling force, F chel• can safely
be used to push coiled tubing into deviated holes, and they are proposing experimen1al verification of 1his
assumption.

Logging operations by Canadian Fracmaster and Esso Resources Canada in British

Columbia have shown that coiled tubing can be safely subjected to buckling forces midway between the
helical and spring limits. Recent experience of at least one of the service companies indicates that the
critical load calculated from helical spring theory, F cspr• is a reasonable indicator of the near upper limit
- of safe compressive forces to use to insert coiled tubing into deviated holes. This force is considerably
larger than the force required to initiate helical buckling. It has been reported that when F cspr was
"exceeded in moderation," no damage to the tubing was observed.

These criteria (Fcsin• Fchel• and F cspr) should be used with caution and as guides rather than
as absolute indicators. Judgment based on experience, though sometimes expensive to acquire, is of great
value when dealing with such concepts as buckling and all its implications. Buckling does not necessarily
imply failure, but indicates the onset of a condition which may precipitate failure.

When more accurate or significant critical buckling load criteria are developed, they will
be incorporated into CSTRESS either in addition to, or as replacements for the three criteria presently
employed.

2.8 HELICAL FRICTIONAL FORCE AND WCKUP

Once coiled tubing becomes helically buckled, the tube body will exert extra normal force against
the wellbore so helical buckling causes additional frictional force called "helical frictional force." The
helical frictional force equation is evaluated in "Frictional Drag Analysis for Helical Buckled Pipes in
Extended Reach and Horiwn1al Wells" (Jiang Wu and Haas C. Juvkam-Wold, 93-PEf-8).

Fhel-fric
= r • (T )2 • A I •f (2-65)
4 •E •I

2-21
where:
Fhel Helical Frictional Force
E = Elastic Modulus
I = Moment of Initial
T = Axial Compressional Force
r Clearance
f Friction Factor
i. I = Segment Length

Equation 2-65 is based on the following assumptions:

1. Axial compressional forces on both ends of the segment are equal which implies that segment
length is relatively short.
2. Originally, this equation was derivated for weightless pipe in a straight wellbore.

When axial compressional force is increased, the equation shows that helical frictional force is
increased as the square of compressional force. This helical frictional force against the tube moving into
the well causes extra axial compressional force for the next (upper) tube segment. If the helical frictional
force is large enough, the compressional force is balanced by the helical frictional force no matter how
much force is applied at the surface. In this situation, the helical buckling section locks and the tubing
string below the helical buckling section cannot move down to the hole.

2.9 TRIAXIAL, BIAXIAL, AND API STRESS ANALYSIS

An element of material subjected to stress ux, uy, and az in three perpendicular directions is said
to be in a state of triaxial stress. A coiled-tubing string subjected to axial load and pressure (external
and/or internal) is in a state of triaxial stress (Figure 2-10).

f~ Fo Axial Lood

Po External
Pressure

cro~~
ar~
I ~~!=~~ I
I I
I I
I I
I I
Figure 2-10. Triaxial Stress State I I
I I
I I
_1I_ _ _ _ _ _ _ 1
I

...- I 1--...
_,... I --- I '
/ (- ~) '

Thickness -l t ~-~~- 1 Pipe ID

Do Pipe OD

U F o Axial Load

2-22
 2.9.1 Triaxial Equation
The generally accepted relationship for the effect of axial stress on collapse or burst is
based on the distortion energy theory. A closed triaxial design procedure has been developed using Von
Mise's and Lame's equations. This present model does not consider torsional effects.
Let E = Elastic Modulus
D0 =Pipe OD
D·I = Pipe ID
ro = Pipe Outside Radius
r·I = Pipe Inside Radius
Us = Yield Stress
u. = Axial Stress
p. = Internal Pressure (psi)
I

Po = External Pressure (psi)

The pipe thickness is

(2-66)

The cross area of pipe wall is

A= T •(D~ - Dn/4 (2-67)

Axial stress contains axial force, bending stress, and helical frictional force. According
to Lame's equation for a thick tube, the hoop stress uh and the radial stress ur exerted by internal and

- external pressures at the cylinder at radius equals r.

(1
r = (2-68)

and

r~P- - r 02 P 0
1 1
(2-69)
2 2
r0 - r;

For most cases, the maximum equivalent stress is at the pipe inside surface. Therefore,
the equation can simplified by letting r = r; and rewriting the equation in pressure and diameter tenns
so the above equations become
(2-70)

- and

2-23
 p. -
I 22 d
[ d 0 - d·I
2
0
2 l p
0
(2-71)

d2
let C (~ and Eq. 2-12 becomes
2 •t • 0
- t)

uh " (C - 1 ) Pi - C • P 0 (2-72)

Von Mises's equation is

(2-73)

where u 1 , u2 , and u3 are three principal stresses, and uy is the equivalent stress according to the three
principal stresses. Because the stresses ur, uh, and ua are three principal stresses, they can be inserted
into Von Mises's equation

2 u~ " [<ua - uh)

2 2 (2-74)
+ (uh - Ur) + (ur - ua>2]
so the equivalent stress uv becomes

Uv " ( 112 (ua - uh )2 + (uh - Ur )2 + (ur - Ua )2) (2-75)

Combine Eqs. 2-70 and 2-71 with Eq. 2-74 and rearrange the terms in the equation.

p "
- u
a
+ 2CP· - P·1
I
±J - 3 u2 - 6 u P· - 3Pf
a a 1 + 4u~ (2-76)
0
2C

or

±J- 3C 2 ua - 6C 2 uaPo - 3C 2 P~ + 4(C 2 - C +

2
l) Uy (2-77)
2 (C 2 - C + I)

In Eqs. 2-76 and 2-77, if uy is replaced with u8 (yield stress), the solutions P 0 and Pi
are the limited collapse and burst pressures.

Mathematically, there are two solutions for P0 from Eq. 2-76 (for positive and negative
square roots), but in practicality only positive real number(s) represent the collapse pressure P0 • There
can be one, two, or no solution(s) for the collapse pressure design. When bending stress is considered,
caused by wellbore dogleg or helical buckling, the u8 in Eq. 2-76 is either:
u8 = Minimum Axial Stress (uamin) = Average Axial Stress - Bending Stress
or
u8 Maximum Axial Stress (uamin) = Average Axial Stress + Bending Stress
This results in the solution(s) for collapse pressure design with minimum and maximum
bending stress effects.

2-24
 Note, when 118 is replaced by "amin and "amax• both "amin and "amax can have the

- positive square root solution. If this happens, the smaller value of the two positive square root solutions
is the upper boundary of e-0llapse design. In the same way, the larger value from the two negative
square root solutions is the lower-pres.§Ufe boundary of the collapse design.

Operating Pressure
positive square root solutions

negative square root

solution
min. operating pressure
---~----+-----+-+<-+- .. Axial Stress
.. ..
·"
·~
"'"'~
~
c;; c;; c;;
Iii Iii Iii

.... ..
·~ ·;; ·x

E Cl E
:J :J
E E
.E ..
·c: Qi> ·~
E

Figure 2-11. Bending Stress Effects on Burst Pres.§Ufe Design

2.9.2 Biaxial Equation

To disregard the internal pressure on e-0llapse pres.§Ufe design, let Pi =0 and Eq. 2-76
is simplified.

~ 2 - 4 (aa2 -
±ua 2
"v) (2-80)
- 2C

If 118 and uy are replaced by "amin (Eq. 2-78), Uamax (Eq. 2-79), and 118 (yield stress),
Eq. 2-80 produces the e-0llapse design pressure for biaxial stress analysis.

Let P0 = 0 in Eq. 2-77 and it bee-0mes

J-
(C - 2)118 ± a~
3C 2 a;
p. = ------'---=-----------­
+ 4(C 2 - C + 1) (2-81)
' 2 (C 2 - C + 1)
The above equation is the burst design pres.§Ufe for biaxial stress analysis.
where

(2-82)

2.9.3 API Equation

API Bulletin, 5C3, 1989, "Formulas and Calculations For Casing, Tubing, Drill Pipe
and Line Pipe Properties" (see for details) lists all API standard equations for axial stress limits, burst
pressure limits, and four collapse pressure range limits.

2-25
 Depending on the D/t ratio (diameter over thickness) of pipe, the collapse-tension curves
for biaxial and API methods are different. Equations 2-68 and 2--09 are called Lame equations, they are
derived from the thick tube stress (small D/t value). The API collapse pressure formula for the plastic
zone is derived by slatistical regression analysis from more than 2400 casing collapse tests. The API
collapse pressure formula for transition zone is determined by the curve fitting. This formula is used
to determine minimum collapse pressure between its tangency to the elastic collapse pressure curve and
its intersection with the plastic collapse pressure curve. The choice of triaxial, biaxial, or API criteria
is left to the user.

2-26
-
3. Tortuosity

- 3.1 MODEL DESCRIPTION

When planning a well, the surveys generated from geometric considerations, i.e., kick-off point,
build rate, path shape, etc., are smooth curves, whereas actual wells contain doglegs and other
irregularities that increase torque and drag. When these "smooth curves" are input into the torque and
drag model, the model predicts torque and drag values that are lower than those in actual wells
containing doglegs and other irregularities.

In the past, when "smooth" curves were used, the friction factors were artificially increased
(e.g., from 0.22 to 0.29) to correspond to the increased torque due to hole irregularities. This technique
gives good approximations of the actual torque, but it has the limitation that it predicts zero torque and
zero frictional drag in vertical portions of the well, regardless of the friction fae10r, because the lateral loads
are zero in these "smooth" vertical sections. The CSTRF.SS program calculates only the drag force.

A very simple and elegant way to handle this problem been developed by Exxon, and was reported
to us by Dr. Rap Dawson.

To add tortuosity to the wellpath, a sinusoidal variation, whose period length (or cycle length) is
""l, is added to both inclination and azimuth angle. This is in the form

Tortuosity = T Sin (2TMD/ 1>.I) (3-1)

where:

T Amplitude or tortuosity number in degrees

MD Measured depth (ft)
1>.I Period length or cycle length for 2T

In addition, the inclination angle is modified so that it will not become less than zero, since
negative inclination angles are not allowed.

The amplitude or tortuosity number T of the sinusoidal variation is varied according to the hole
conditions. Exxon has found that a tortuosity of T = 1 represents typical field conditions.

If the untortured survey data are of equal space and the value of measured depth for each survey
1
station is n x ; where n is any integer, then after calculation the survey data will not be tortured.

3-1
 Thi s 1s . Eq . 3- 1 where MD = _n 'i.l
. ven"fied m _ , then tortuos1ty . th
. added to .mel"mau· on and az1mu
2
for each survey will be:

Tortuosity T • sin (2T •MDIi. 1)

. n•i.l 1
T • SID (2T • - - • ­
2 i.l
T • sin (n • T)
= 0
Total dogleg added to the original survey depends on the survey data, Amplitude T, and period
length. The amplitude or tortuosity number (T) is the maximum possible degree added to or subtracted
from inclination and azimuth.

It is recommended that L>I be chosen to do at least five times the interval between survey stations.

3-2
 4. Program Installation

4.1 BEFORE INST ALLING

4.1.1 Check the Hardware and System Reauirements

CSTRESSl is written in Visual Basic•. It runs in either standard or enhanced mode of
Microsoft Windows 3.1 or higher. The basic requirements are:

• Any IBM-compatible machine built on the 80386 processor or higher.

• Hard disk.
• Mouse.
• CGA, EGA, VGA, Hercules, or compatible display.
• MS-DOS version 3.1 or higher.
• Windows version 3.1 in standard or enhanced mode.
• An 80486 processor and VGA display is recommended.

For assistance with the installation or use of CSTRESSl contact:

Lee Chu or Gefei Liu

Maurer Engineering Inc.
2916 West T.C. Jester Boulevard
Houston, Texas 77018-7098 U.S.A.
Telephone: (713) 683-8227 Fax: (713) 683-6418
Telex: 216556

4.1.2 Check the Program Disk

The program disk is a 31/z inch, 1.44 MB disk containing twenty files. These twenty files
are as follows:

SETUPKlT.DL MDICHILD.VBX
VBRUNlOO.DL CMDIALOG. VBX
VER.DL CSGDB.DB
GSWDLL.DLL CTDB.DB
GSW.EXE CDRAG4.EXE
SETUP.EXE TEST.CDR
SETUPl.EXE TEST.WDI
SETUP.LST TEST.SDI
GRAPH.VBX TEST.CT4
GRID.VBX TEST.CP4

4-1
 We recommend that all .VBX and .DLL files, that have the potential to be used by other
DEA-67 Windows applications, be installed in your Microsoft Windows\SYSTEM subdirectory. This
applies to all the . VBXs and .DLLs included here. The CSTRESS 1 executable (CSTRESS I.EXE) file
should be placed in its own directory (default "C:\CSTRESSI "). All these procedures will be done by
a simple setup command explained in Section 4.2.

In order to run CSTRESSI, the user must install all the files into the appropriate directory
on the hard disk. Please see Section 4.2 to setup CSTRESSI.

It is recommended that the original diskette be kept as a backup, and that working diskettes
be made from it.

4.1.3 Backuo Disk

It is advisable to make several backup copies of the program disk and place each in a
different storage location. This will minimize the probability of all disks developing operational problems
at the same time.

The user can use the COPY or DISKCOPY command in DOS, or the COPY DISKETIE
on the disk menu in the File Manager in Windows.

4.2 INSTALLING CSTRESSI

The following procedure will install CSTRESSI from the floppy drive onto working subdirectories
of the hard disk (i.e., copy from B: (or A:) drive onto C: drive subdirectory CSTRESSI and
WINDOWS\SYSTEM).

1. Start Windows by typing "WIN" <ENTER> at the DOS prompt.

2. Insert the program disk in drive B:\.
3. In the File Manager ofWIIXlows, choose (RlDI] from the [File] menu. Type B:\setup anl ~ Fnler.
4. Follow the on-screen instructions.

This is all the user needs to setup CSTRESSl. After setup, there will be a new Program Manager
Group (DEA APPLICATION GROUP) which contains the C.T. icon for CSTRESSI as shown in
Figure 4-1.

4-2
--
DEA APl'UCATION GROUP' '

ID LI DI ~-
~-·
CSl!essl Tritucl Aesrr.od4

-D IAl m
CEMENT fM)MOO 2.1 wekon2

rn
Mon Pr
~ t;oJ ii I

00<etde BUCKLE! r.-.,,.1

su... •
Mic:rosdt Tooll SlartUp

tml•
Appicalicns
m•
Mic:1molt.
rn•
Miaosoft
vii:umBasic A<:ceu

Figure 4-1. DEA APPLICATION GROUP and "CSTRESSl" Icon

4.3 STARTING CSTRESSl

4.3.1 Start CSTRESSl from Grouo Window

To run CSTRESSl from the GROUP Window, the user simply double-clicks the
"CS TRESS l" icon, or when the icon is focused, press <ENTER>.

4.3.2 Use Command-Line Option from Windows

In the Program Manager, choose [Run] from the [File] menu. Then type
C:\CSTRESSl\CSTRESSl.EXE <ENTER>.

4.4 ALTERNATIVE SETUP

If the SETUP procedure described before fails, follow these steps to install the program:

1. Create a subdirectory on drive C: C:\CSTRESSl.

2. Insert the source disk in drive B: (or A:).
3. Type: CD\CSTRESSl <ENTER>.
4. At prompt C:\CSTRESSl, type:

- Copy B:\CSTRESSl.EXE <ENTER>

Copy B:\*.DB <ENTER>
Copy B:\TEST.* <ENTER>.

4-3
5. Type: CD\WINDOWS <ENTER>.
6. At prompt C:\WINDOWS >, type:
Copy B:\VBRUNlOO.DL_ VBRUNlOO.DLL <ENTER>.

7. Type: CD\WINDOWS\SYSTEM <ENTER> .

8. At prompt C:\WINDOWS\SYSTEM>, type:

Copy B:\*.DLL <ENTER>
Copy B:\*.VBX <ENTER>.
Copy B:\GSW.EXE <ENTER>

9. Type: CD.. <ENTER> then key in "WIN" <ENTER> to start Windows 3.1 or later
version.

10. Click menu "File" under "PROGRAM MANAGER," select item [New ...] click on [PRO­
GRAM GROUP] option, then [OK] button.

11. Key in ''DEA APPLICATION GROUP'' after label ''Description:,'' then key in ''DEAMEI''
after "Group File:," then click on [OK] button. A GROUP Window with the caption of
"DEA APPLICATION GROUP" appears.

12. Click on menu [File] again, Select [NEW...] click on "PROGRAM ITEM" option, then,
[OK] button.

13. Key in "CSTRESSl" after label "Description," key in "C:\CSTRESSl\CSTRESSl.EXE"

after label "COMMAND LINE," then click on [OK] button. The CSTRESSl icon appears.

14. Double-click the icon to start the program.

4-4
-

·­ 5. Basic Operation of Microsoft Windows

CSTRESS l runs in a Microsoft Windows environment. It is assumed that the user is familiar with
Windows, and the user's computer is equipped with Windows 3.0 or later version.

Some elements and terminology of Windows are reviewed here:

r- Ml:umi:tt Bo.x
,....- Control Box r- Tit!• Bar _ Ma.'Ximi:e Box

or
-I Output
Restore Box
file Window Graph .QpUon Jielp
..tescade .• Shlft•f!i
Ille Sh11HF4
Arrange icons
ALL
fquivalent Stress
ttydraullc Pressure
~al Drag
.Surface. Load
13.ottom Hole Pressure
(!ala Table
Bl-Axial Graph

Figure 5-1. Title Bar in Window

S.1 THE TITLE BAR

The title bar serves two functions: one is to display the name of the current window and the other
is to indicate which window is active. The active window is the one whose title bar is in color. (On
monochrome monitors, the difference is shown by the intensity of the title bar). The user can make a
window active by clicking anywhere within its border.

S.2 THE CONTROL BOXES

At the left side of the title bar is the control box. It has two functions. First, it can display the
CONTROL menu, which enables the user to control the window size using the keyboard. Second,
double-clicking the control box will end the current program.

During execution of CSTRESSl, the control boxes are not needed. The program will run
according to its own flow chart.

S.3 MINIMIZE AND MAXIMIZE BOXES

At the right side of the title bar are the MINIMIZE and MAXIMIZE boxes. The box with the up arrow
is the MAXIMIZE box. The box with the down arrow is the MINIMIZE box. If a window has already been
.-- maximized, the MAXIMIZE box changes to a RESTORE box with both up and down arrows, as shown in
Figure 5-1.

5-1
 • Clicking on the MINIMIZE box will reduce the window to the size of an icon. The window's
name in the title bar appears below the icon. To restore a window from an icon, double-click
on the icon.
• Clicking on the MAXIMIZE box will make the window take up the total working area.
• Clicking on the RESTORE box will make the window take up a portion of the total working area,
which is determined by how the user manually sizes the window.

5.4 TEXT BOXES

TEXT boxes can display the information that the user enters. Sometimes there will be text already
typed in for the user. The user can utilize arrow keys to edit the existing text. Figure 5-2 shows a
typical text box.

Company Name: _Maurer Engineering Inc. ·­

Project Name: DEA 67
Well Name : Slimhole
Well Reid: Coiled Tubing
Well City I Sfate : Houston Texas
Date: 11993Apr
Comments: E11ample

Figure 5-2. Text Box

5.5 CHECK BOXES

A CHECK box indicates whether a particular condition is on or off. When it is on, an X appears.
When it is off, the box is empty. Figure 5-3 shows a typical check box.

- Calculation 0 ption:

IZI Include A&M buckling criteria

IZI Include helical frictional force

IZI Include bending stresses

Figure 5-3. Check Box

5-2
-
,_., 5.6 OPTION BUTTONS

OmoN buttons are exclusive settings. Selecting an option immediately causes all other buttons
in the group to be cleared. Figure 5-4 is a typical option box.

!Azimuth:

@Angular

0 Oil Field

Figure 5-4. Option Buttons

5.7 COMMAND BUTTONS

A COMMAND button performs a task when the user chooses it, either by clicking the button or
pressing a key. The most common command buttons are the OK and Cancel buttons found on almost
every dialog box. In most cases, there is a button with a thick border-the default button which will be
executed if you press <ENTER>. Figure 5-5 shows a typical command button:

Edit

[ I _
. _ !nsert
_ Line ___, )lelete Line

T orluosity...

Figure 5-5. Command Buttons

5.8 LIST BOXES

A UST box gives the user a list of options or items from which to choose. If the UST box is too
small to show all possible selections, a SCROLL box will appear on the right side of the box. The user
makes a selection from a UST box by clicking on it, or from the keyboard, highlighting the desired item
with the arrow keys, and then pressing <ENTER>. Figure 5-6 is a typical list box.

Light Green
Light Cyan
Light Red
Light !-4agent
Light Yellow
Define Color ·~·

- Figure 5-6. List Box

5-3
5.9 DROP-DOWN LIST BOXES

A DROP-DOWN LIST box is indicated by a small arrow in a box to the right of 1he option. The
current setting is shown to the left of the arrow. When 1he user clicks on the small arrow, it drops to
list all selections. A typical drop-down list box is shown in Figure 5-7.

!
Nozzles:~
Nozzle Sizes. ·.·. . ·... ·. ·f···..•
Nozzle Si2et
TFA
Figure 5-7. Drop-Down List Box

5.10 SCROLL BARS

SCROLL BARS are graphical tools for quickly navigating through a long line of items. There are
two types of scroll bars: HORIZONTAL and VERTICAL SCROLL BARS.

The small box inside the bar is called the SCROLL BOX. The two arrows on the ends of the scroll
bar are scroll buttons (Figure 5-8). Clicking the scroll buttons or moving the SCROLL BOX will change
the portion of the information you are viewing.

I t~I
Figure 5-8. Scroll Bar

5.11 GRID

GRID displays a series of rows and columns (Figure 5-9). In case of a long list of items or a large
amount of information, scroll bars will attach to the grid providing easy navigation.

O.D.
(in)
11.D.
llin)
l'Wt in air
Ilib/ft)
IDensit.P
lllb/ft3J
IElastic
l[psi)
IYield
l[psi)
-+
32 2.000 1.688 3.on 490.0 30000000 70000
33 2.000 1.624 3.638 490.0 30000000 70000
34 2.000 1.594 3.896 490.0 30000000 70000
35 2.380 2.157 2.638 490.0 30000000 70000
36 2.380 2.125 3.004 490.0 30000000 70000
37 2.380 2.107 3.207 490.0 30000000 70000
38 2.380 2.063 3.697 490.0 30000000 70000 .__
39 2.380 1.999 4.391 490.0 30000000 70000 .__
40
41
2.380
2.880
1.969
2.625
4.709
3.671
490.0
490.0
30000000 70000
30000000 70000 -
+

Figure 5-9. Grid

5-4
- In the INPUT Window, grids are used to let the user input data. Some columns of grid only allow
number input. Typing of an alphabetical character is prohibited by the program. The user can edit an
entry by typing desired characters or pressing the <BACKSPACE> key to delete. In many grids, just
like a spreadsheet, the user can insert and delete a row.

On the other side, grids are for presentation only in the OUTPUT Window. They do not allow
editing.

The grid supports word-wrapped text presentation, resiuable columns and rows, etc. Even though
the user can manually change the cell's column width or row height, we do not recommend this because
all grids in CSTRESSl are carefully designed to fit the length of the appropriate data string.

--
5-5
5-6
- 6. Running CSTRESSl

CSTRESSl runs in Microsoft Windows environment. Windows' graphical user interface (GUI)
and point-and-click environment gives the user the flexibility that is needed for today's software.

6.1 OVERVIEW

There are two major windows in CSTRESSl:

1. INPUT-CRITERIA Window
2. OUTPUT Window

Only one window can be shown on the screen at a time. The menu bar, control button, arrow
keys, hot keys, etc., can be used to control the program's flow and the keyboard or mouse to input the
data. F.ach major window contains several sub-pages or sub-windows to hold different groups of input
and output information.

The menu bar selection is not always available in certain sub-pages or sub-windows. This type
of design is to reduce the possibility of destroying the program in operation flow.

- II FILE

New Project
MODEL
TABLE 6-1. Input Criteria Window Menu

Pick up (Logging)
PAGE

Next - F11
RUN

Start
CUSTOMER UTILITY

Foreground Color
HELP

Assistance
II
Open Project Slack off {Logging) Previous - Fl 2 Background Color About
Save Project Pick up (Drilling - Tripping) First Monochrome
Save Project As... Slack off (Drilling - Tripping! Last English
New File Drill Metric
Open File Consider Hydraulic While Tripping Well bore
Save File
Save File As ...
Print•,
Current Page
All Pages
Exit

TABLE 6-2. Output Window Menu

FILE WINDOW GRAPH OPTION HELP

Print Report/Graph Only Cascade - Shift F5 Curve Option Assistance

Print Project File Tile - Shift F4 Image File Format •, About
Bitmap
Metafile
Print WCI and SDI File Average Icons
Print TOI and POI File All
Copy Graph to Clipboard Equivalent Stress
Save Report Disk File Hydraulic Pressure
Back to Input Axial Drag
Exit Surface Load
Bottom-Hole Pressure
Data Table
Bi-Axial Graph

6-1
6.2 GEITING STARTED

Bring up Wumws anl select "DEA APPllCATION GROUP" ~Ire active winklw, ~ s00wn in Figure 6-1.

.. 1, ' DEA AFPt.JCATION GROUP I·• ._

II •
CSbeu1 1~
II T~1
1=
Reomod4

D
CEMENT
l.~I
H'l1>MOO 2-1

[ffiJ•
Main Pi
~ l~ol a
--
BUCKLE1 rq.-1

rn• e..so...
­
Micmsdl Toca
---
StmtUo
VSIUOI oasic:
10

m•
Games
[ffiJ
•
,,....,......

Figure 6-1. "DEA APPLICATION GROUP" and CSTRESSl Icon

This window may contain more than one icon. Double-click on the CSTRESSl icon, the
INTRODUCTION window with two command buttons, "Exit" and "Continue" will be displayed on the screen.

=L-1 lntroduction
-
1~ ­
.
..!!!.. ~

Cailad Iubing SDI& Aoablii& MDdEll (CSIUlll ~ Dl

C.T. Stress/ Drng I Buckling I Hydrnulics Model
DEA-67
Ptojod lo D'""'op and Evaluate Slioo-Hole and
Cailed-TulMng T echnologp
By
Maw•• Engfttering Inc.

TIU .,_igliled 19S3 conli-el r - a n d - -­

•• lor the a'8 use ol P.ticip.U Gift llhe DrAng Engilwering
Aa:ucielion DEA-67 proied1 .,.. ttm llffiietec. and .., not to
be cildoaed to att.. pmtiea. Dete output Ira. lhe PIOCI'- can
I I
be disdo•ed lo the UWd ..,W.. Perticiponl• <nd their ""iiole•
•• lree lo . - . copi9s of a.a report and imoura• for ttm in-
hounuaeanly.
M-..m EnP-ering Inc....... no _ ,..., 01 •••aenlalion.

Ace
I eilher e11q11e•sed Of illplied. with respect to the progr- or docu­
....tlll.ion.. induding lheir quelil,. pedm-.ce. -cheMbilitJ.
or fineaa lor e particular putpose.

E
G
I J;onl- I I
E.m I
VtiuaiBai:ic Ac<ot•

Figure 6-2. Introduction Window

6-2
- Clicking "Exit" will terminate the program. The "Continue" button is the default command which means
that the user can press the button by pressing <ENTER> or clicking the mouse. This will invoke and display
the INPUT Window. Note that after the INTRODUCTORY Window appears, it takes a few seconds for the
command buttons to be responsive; it is loading necessary files.

6.3 PULL-DOWN MENUS IN THE INPIIT WINDOW

The CSTRESSl menu system provides many tools that the user will utilize while running the application.
As in other Windows applications, the user can pull-down a menu by clicking the menu name with the mouse,
or by pressing the Alt key on the keyboard and then striking the first letter or the underscored letter of the menu
name. Once a menu is displayed, the user selects a command by clicking the command name with the mouse
or by highlighting the command name and pressing <ENTER> .

There are six menus in the INPUT Window: File menu, Model menu, Page menu, Run menu, Customer
Utility menu, and the Help menu as shown in Figure 6-3.

-I Input· ICrlte~a Wlndowj

file Model E'age Bun Customer l.ltlllly J:!elp

'- Figure 6-3. Input Window

The page number is shown on the right-hand side below the menu bar. These five pages are illustrated
in detail in the next section. The Page, Run and Help menus are enabled for five pages. Model and Customer
Utility menus are enabled only on the first page. However, the last item "Wellbore" under Customer Utility
can be selected only on the fifth window page.

For the File menu, the four commands on project file ("New Project," "Open Project. .. ," etc.) are
enabled only on the first page while the four commands on file ("New File," "Open File... " etc.) are enabled
only on pages 2 through 5 of the INPUT Window.

6-3
 The File menu contains commands for creating, retrieving, saving and printing input data as displayed in
Figure 6-4.

-I Input - [Criteria Wlndowj

flle Model E'age Bun Customer J.!tillty Help
Hew Project P-1ol5
Jlpen Pro)eCL..
Saye Project
s~ Project A.a•.•
Ne'tii!t: File
Open File ...
~·""' Flle
Save Flle As••.
f'rlnt•• •
Elllt

-I Input - [Criteria Window!

Elle Model E'age Bun Customer J.!tlltty Help
Hew Project P-1ol5
Jlpen Pro)eCL.•
Saye Project
Savi: Project As •••
N"'ll File
Open File ...
~ave Flle
Save Flle ,4s...
f'rlnL .. · I Curren~~ge·.:1
I All Pageo
E111t

Figure 6-4. File Menu

When the user starts CSTRESSl, it automatically opens a new project (by default: Projectl.CDR) and a
set of input data files, namely, Projectl.WDI, Projectl.SDI, Projectl.CT4 Projectl.CP4, all in the current
subdirectory. The reason for using the project file is for quick, future retrieval of a set of input data_ The user
can open an existing project file without opening each individual (.WDI, .SDI, CT4, _CP4) file. The project
file, which is a collection of the paths and file names of all input data files, will do the rest of the retrieving
work for the user.

However, although the listing in the CRITERIA Window (Page 1) represents files, CSTRESSl does not
automatically create files on the disk when the user starts CSTRESSl. The same is true with "New Project."
Only when the user chooses one of the Save commands from the File menu does CSTRESSl actually save
something to disk.

1. "New Project" command clears every input data file and displays a set of null input data files with
default names in the CRITERIA Window.

2. "Open Project. .. " command opens a dialog box which enables the user to explore the file system for
input files with extension name ".CDR."

6-4
- 3. "Save Project" command replaces the previous version of each of the input data file in the project with
the modified one. Note that the project file (.CDR) does not contain any input data. It is simply a list
of all the input data files in the project. That list is updated every time the user saves the project.

4. "Save Project As... " command opens a dialog box. The user can specify the drive, directory, and the
name of the project tile.

5. "New File" command clears every entry box associated with the current page, (i.e., one of WDI, SDI,
CT4, CP4 files).

6. "Open File ... " command opens a dialog box which enables the user to explore the file system for input files
with exten&on name which is determined by the current page the user is in. For example, in page 2, the
user clicks the Open File... ; the pattern for the file list box in the dialog box will be •'. WDI. ''

7. "Save File" command replaces the previous version of the input data file.

8. "Save File As... " command enables the user to save a file under a new name the user specifies while also
retaining the original file. The new file will be associated with the project file when the user saves the
project.

9. "Print" command allows the user to print the input data of the current page or all pages.

- 10. "Exit" command terminates the current application. CSTRESSl will prompt the user to save the
files, if they are not saved.

The files that make up a project do not have to be in one directory on the hard drive, since the project
records the detailed path information on each input tile. A single file such as an SDI tile can be part of more
than one project. However, if the user renames or deletes a file outside of the CSTRESS 1 application and then
runs CSTRESSl and tries to open the file, CSTRE.5Sl displays an error message to warn the user that a file is ~.

The Model menu contains commands for five different coiled-tubing operations as displayed in Figure 6-5.

-I Input- \Crlteri• Wlndowj

file Model eage Bun Customer \ltlllty l:lelp
· · Pick up (Logging! Page 1ol5
./Stock off (logglngJ
Pick up (Orilllng-Trlpplng)
Stock off (Orillin11Trippin9J
I Drill
I .J Consider hydraulics wt.lie tripping

Figure 6-5.

1. "Pick Up (Logging)" operation allows pick up of the coiled-tubing string with the logging tool

-
connected at the end.

2. "Slack Off (Logging)" operation allows the coiled-tubing string to be run into the well with the
logging tool.

6-5
 3. "Pick Up (Drilling-Tripping)" operation allows pulling the coiled-tubing string together with the
bottom-hole assembly out of the well.

4. "Slack Off (Drilling-Tripping)" operation allows slack off of the coiled-tubing string with BHA.

5. "Drill" operation simulates the drilling operation.

6. "Consider Hydraulics While Tripping" tells the program to calculate only the hydrostatic pressure or
to calculate surge and swab pressures (pick-up, slack-off operations) and circulating pressure (drilling
operations). The check mark has to be at the front of this command or it will only calculate hydrostatic
pressure.

The Page menu contains commands for browsing and navigating through the five pages as displayed in
Figure 6-6.

-I Input· [Cr11er1o Wlndowj

eo~~ous ~ ~···i Customer l,ltillty

Ell• Model Help
Bun Page 1ol5

f)rs1
I Last

Figure 6-6. Page Menu

1. "Next" command leaves the current page and goes to the next page. Before doing so, the program
will first check the validation of the input data in the current page and asks if the user wants to correct
the invalid data entry. Then it will prompt the user to save the current file if it has not been saved.
2. "Previous" command functions the same as "Next" command, but in the opposite direction.
3. "First Page" command leaves the current page and goes to the CRITERIA Window. It will check the
input data and prompts the user to save the file if the file on the current page is not saved.
4. "Last Page" command leaves the current page and goes to the PARAMETER DATA INPUT Window.
It will check 1he input data aIXi prompts 1he user t> save 1he file if 1he file on 1he current page is mt saved.

Usually, if all data are matched and consistent, the user will have no problem leaving one page for
another. However, in some cases, the program will prompt a warning message even though each individual data
page is good. One possibility is that an existing file is opened on the first page (Criteria page), and the user
moves to the last page without going through the preceding pages. The program has no knowledge of the
validation of 1he data in preceding files. In 1his case, going through 1he preceding plges will help clear 1he confu.9on.

The Run menu contains the command that the user chooses when ready to start calculation. The "Start"
command does just that. The user can start the calculation from any page. The program will check the
validation of all data.

6-6
-
-
- The Customer Utility menu contains the command that enables the user to select the color, unit, and
wellbore schematic.

Figure 6-7 shows this menu.

-I Input· (Parameter Oat• Input Window! 1-1;

file Model E;ge Bun Customer !!tJllty ·. . •. Help
Foreground Color P-5ol5
Background Color
~nnochrom'~

-'English
Mt: tile
Wellbore.••
-­
Figure 6-7. Customer Utility Menu

1. "Background Color" command opens the "Color" dialog box, which will let the user select the
desired background color.
2. "Foreground Color" command opens the "Color" dialog box, which will let the user select the
desired foreground color.
3. "Monochrome" command allows the CSTRESSl program to run with a monochrome monitor.
4. "English" and "metric" menu allows the user to select the desired unit.
5. "Wellbore" command shows the wellbore schematic.
The Help menu gives the user information about the assistance and computer systems.

Figure ·6~8 shows this menu.

-I Input · !Criteria Wlndowj

flle Model f-ge Bun Customer \ltllity Help
Asslatance ...
About. •.

Figure 6-8. Help Menu

1. "Assistance... " command opens the "Assistance" dialog box, which displays MEi's address, phone
number, and other applicable information.
2. "About... " command opens the "About" dialog box, which gives the user instant reference
information about CSTRESSl and current computer system information .

-
.

6-7
6.4 THE INPUT WINDOW

In the INPUT Window, there are five pages according to different input data files. These five pages are:
1. CRITERIA Window
2. WELL DATA INPUT Window (WDI)
3. SURVEY DATA INPUT Window (SDI)
4. TUBULAR DATA INPUT Window (TDI)
5. PARAMETER DATA INPUT Window (PDI)

When the user leaves each page, except the first page, the program automatically checks for input errors
on that page.

6.4.1 Page 1; Criteria Window

Figure 6-9 shows a typical CRITERIA Window. The paths and names of input data, their saved
status (Saved or Not), CT operating model, hydraulics consideration, and the unit system currently in use is
displayed on this page.

-I Input -1cr11er11 Wlndowf

Elle Model fage Bun Customer Utlllly Help

Coiled Tubing Stress Analysis Model (CStress)

Project file: C:\VB\CH\TEST.CST (>)

Well Dme. Input file: C:\VB\CH\TEST.WDI (>)

SuNBy Data Input file: C:\VB\CH\TEST.SDI (•)

Tubular Data Input file: C:\VB\CH\TEST.CT4 (•)

Parameter Data Input file: C:\VB\CH\TEST.CP4 (•)

Model Selection: Slack all (Logging) (Consider Hydraulics)

Unit Syotem Used: Engli&h

Note: (•) • Savad. (-) • Not savad

Figure 6-9. Criteria Window

6-8
-
6.4.2 Page 2; Well Data Input <WDD
Figure 6-10 shows a typical WELL DATA INPUT Window.

~1 Input· IW•ll Date Input Window!

fll• Mod•I flu• Bun Cuatam•r Utlllly tl•IP
C·\VB\Ql\JESI 'WDI

Company Name : !'A aurer Engineeril'.!9Jnc,______

Project Name : DEA67
Well Name: Slimhole
Well Field: Coiled Tubing
Well City I State : Houston Texas
Dale: 1993Apr
Comments: Example

Figure 6-10. Well Data Input Window

The user is asked to input a series of strings representing the company name, project names, well
location, data, and comments. They are optional and need not be completed. They will not be used in
- calculation or in the file name specification.

The strings must be less than 30 characters in length.

6.4.3 Page 3; Survey Data Inout <SDD

Figure 6-11 shows a typical SURVEY DATA INPUT Window.

-I Input - !Survey Dote Input Window!

Ell• Model flu• Bun Cuatom•r Utlllly tl•lp
C·\YB\CH\TEST SDI

Uni tm:unlilo ~ l!unud IDGinl!iln ~

Rmtlb ~ oWlt.

,...Depth:­ 1 0.0 0.00 0.00 •

@Feel 2 1111.0 0.00 0.00
3 400.0 0.00 0.00
0Mol•
' 5
800.0
1200.0
0.00
0.00
0.00
0.00

·1nc-ion:l
@o..-..
6
7
1600.0
2000.0
0.00
0.00
0.00
0.00
8 2400.0 0.00 0.00
Oooa. Min
1 9
10 3200.0
2800.0 0.00
10.00
0.00
0.00 ..
[E*
~ I
(nserl Line D.-•Line
0 OiFmld
Tortuo1ilJ_ ..

Figure 6-11. Survey Data Input Window

6-9
 The user can input up to 400 survey data points. The measured depth, inclination angle and
azimuth angle each have two unit options, independent of the application unit system the user selected for the
application.

When the cursor is in the text box, press the +- or ... key to move the cursor inside the box to edit.
Pressing the t or i key will move the cursor to the above or the lower box. If the user wants to move the
cursor to the right or left box, hold down the Ctrl key and press ... or +-. Of course, the user can use the mouse
or press the tab key to locate the cursor.

The SDI files used in CSTRESSl are compatible with any SDI files in other DEA software
applications developed by MEI.

The tortuosity command button lets the user torture the smooth survey data, so that the doglegs add
to the original survey. See Section 6.8 for details.

6.4.4 Page 4: Tubular Data Input ITDD

Figure 6-12 shows a TUBULAR DATA INPUT Window.

=I Input· [Tubular 0"'8 Input Window]

Elle Model Eage Bun Customer l.lUllty Help
C·W!!\CH\JESI CT4
SDI IND lltl 111100 0 lllol 11.D. IHI I 8000 I
Tuhular Del• n•.,. boUontl:::;::;:::::;:::;;:::;:=;::;:=;~::::::;;=:;::;::;:;::::::;:::;:::::;::::;:::::;;::==::::::;i
No. DensilJ I 0.0. I 1.0. I W. M I L__.. I E I Yleld I Acc.. L
8 llblft31 I lint I rnl I llbJlll I lftl I lasil I ,.,.;, I IHI
1 490.0 1.500 1.250 1.836 4000.0 30.0E.o& 70000 4000
~ 490.0 1.500 1.232 1.955 3950.0 30.0E.o& 1111000 7950

°""'
Dal:a Base...

1-N<>nlo."
~~fe::'.o11::-~1:"'.oo1~0:'.'.
logging I ool lnl...mM>no
logging I ool lenglh(ft) I 50.0 I INozzle Sizet I! I
I
::':=====~,~~N::'...i~~-~C~J'."::=====::::::::
Logging I ool llloighl(lbll . 300 ..

.
IDrag(lbll
=~~--~-~~~
300 I I
....
-
......
!~11-..t~woiphll-·
~eea~I~1~----11 + No.

­__..!.__
(l2ndl
:~
12.
11..t Outsido CT: 4 12.
~-----------' ~111=..i"'-~·"'"°""''eea,,,.,_1_,_I--'1=0=.1111=--.__JI -S 12.
.-Weight Ol'I Bil·------~ "'"H)'Clraulica Model: TFA [n2)
0 P-i.- @ B - - ----~
IW•iah! ... Bilflbl) I 5000 I I I
=~~~~~-~~~ I~ i:~001•21 I ~7o: I I 0-AI I

Figure 6-12. Tubular Data Input Window

The spreadsheet-like Tubular Data table is similar to the SDI file input, but TDI uses grids instead
of text boxes which are used in SDI.

6-10
.­ Depending on which model has been selected, the user can input only a fraction of the data
window. The TDI Window groups the same type of input data and places them into frames. For example, if
the user selects the slack off (logging) model, the nozzle and weight-on-bit information is not needed on the
screen. The tide color of 1he llOll-eS\lential frame groop becomes gray shading. The user canmt ac.ces; 1hese datl.

BHA and CT string data are input into the Tubular Data table. The Tubular Data table input starts
from bottom tool (BHA) to the surface. While the user edits the section length, the program continues to track
the accumulative length of the CT string and BHA, then displays the accumulative length (i.e., Well MD) in the
upper center of the screen. When the user selects the logging model, the logging tool length with the CT string
length and/or BHA length becomes the Well MD.

At the top right-hand comer of the TDI Window, the program displays the SDI TMD which is the
total survey measured depth input in the previous SDI Window. The Well MD must be smaller than or equal
to the SDI TMD.

Sometimes when the user switches from one unit system to another, the previously compatible data
may become unmatched due to the rounding off of the data during the conversion operation. Mostly this happens
on measured depth in the SDI file and bit depth in the IDI file. Remember that the unit for measured depth in
the SDI file may be different from the one in the application unit system.

If the user clicks the Database command button, the program opens the disk database file. The
- default file name is CDDB.DB.

-I Input- [Tubuler Debi Input Window]

file Madel 01ge Bun Cuatomer Utility Help
C·\VB\Dl\JEST CJ4
SDI TMD (Ill 00111.0 "'• .. ..
D 1111 I ..OU I
...r. . . o... n.... bottGml:
No. D-1 D.D. I l.D. I W.• 1 L - 1 E I Y-oold Acc. L I II
•
1
111/1131 I
490.0
r.,1 I r.,1 I llb/111 I IHI I • - • I lnlil IHI I
I,_,

..-
z­ 490.0 -I CT DotaBne Open
Fi•K-:
I I
I-
D.irectDl'ies: Oil: f
lr:tdb.db I c:\vbldl
I c..n..1
"""-db ......
--
l.fL.
IO c:\
Logging Tool lnl°" (Ovb -
~ch
llo...-...Toal L­
11---.... ToalW..i.n O:!l
~eon . . Tool Draa: - - :c
Dr--fl Li" n .. o1 .Uoe: D1~1:

I
lcr DB~- ICTDB.DBI [!] 1Elc:leechu66 ltl
~weJ,gl\~ an l•it iH,.troulic:o Modolo TFA 1"'21
OPowmLM1 ® B - - l i c I I
lllfeigh! on Bil!.. J I 5IDI I
lpy'1!!!1100112)
:yp ""' I
12-0
5.00 I I Cle•AI
I
­
.
llOOIJI :>elllcater. ::>..:.. oft llogg1n1J -\AllSI ...

Figure 6-13. Open CT Database File

I

6-11
 Click the OK button, the coiled-tubing database shows on the screen. The user can edit the data
and save the changed data on the disk file. After finding the data, click the OK button, this will copy the data
to the TDI table.

Input - [Tubular Debi Input Window]

flle Model eaue Bun Customer l.!Ullty Help
C·\118\Dl\JESJ CU
Wei 11.D. (HJ 8000
Data Base

1.688 JOOIDDI 1llOOO

1.624 JOOIDDI 1llOOO
1.594 JOOIDDI 1llOOO
2.157 JOOIDDI 1llOOO

-
2.125 JOOIDDI 1llOOO
2.107 JOOIDDI 1llOOO
2.1163 300IDDI 1llOOO
1.999 1llOOO
1.969 300IDDI 1llOOO
2.625 JOOIDDI 1llOOO •
DI: c:...c.i 1......1R.... DeleleRo.

Figure 6-14. Coiled-Tubing Database

The PDI Window also provides the casing database (Figure 6-15).

-I Input - !Parameter Dato Input Window]

file Model eaue Bun Customer ].!tlllty Help
C·\YR\CH\TEST tp4

Data Base

Casing Data Base

•
0.545
0.297
0.350
0.400
0.450
0.495
0.333 11.1184
0.315 11.000
0.435 10.8811
60.000 0.489 10.112

DK ln•ed Row Dlllete Row 1lorce

FkW4f H~-----rr-r:Cald.OOn:-:-.,...,.,.---,0.-:-erv-.-=.....,.-=:-:---r,..,.-------~
...
I (up!!) 10.00 I 11.D. of inleresl

llodel Selected: Slack off !Logging) -C....- H,dreulics

Figure 6-15. Casing Database

6-12
 The default database file is CSGDB.DB

6.4.S page S; Parameter Data Input <PDD

Figure 6-16 shows a typical PARAMETER DATA INPUT Window.

-I Input- (Parameter Diii• Input Window]

fll• Madel fag• Bun Cualomer IJdllty Help

........._..
s-.• .
\v'ol 11.D. (HI 11110.0
(Ir­ ...d-~

IFr.:. P.(psl]

.-­
181 ..n.oc1... - ­ Al Well 11.D.: P•o P.(psij 13000 15000

No. Oe-n-ion I F- I l.D. I Frie. I ..... p I Fi-=- p

I,_, I ,,..;, In-
I lftl I r..1 I

r ,__.!_
2 -hole 5000.D
7.000
6.1110
0.21111
D.300 1500
20111
3500
D-
l:loor

Det:aa......
1

rl:ablo Weigh!:
I !flbJllJ I 0.3H
l[-...s""occ"'-Io:
I l!e!!I 500 I
1-c:..w;.., Option:

.-Swf-=eE~Drag:
181 lncludo Al.II buckling aileri.o
IT.-.0 llO¥ing Sp-~ ISl<Ming Bo.01og
IPtim! I R... B-*Toneion ll>ll
1(111) I 71111
300 I 1811- - lriclianol lorce

.­
1111.0D}
.... Calculltian Abibuta:
181 lncludo bending ..._
[!'low Aate: • I Tube de.... incre. llftl I 5111.0

I 111!!!1 I 10.111 1 I
IC<rlcMtian o....
111.D. al inlo'"'I
11111
IPtl
I
I
1111.0
7950.0 I
...... Soloctod: Slor:t alt (Leaaing) -C...- Hydr..­

Figure 6-16. Parameter Data Input Window

In POI the user finds the same input styles as in TOI, the data are grouped by frames. Some of
these frames can only be accessed with certain operating model selection.

Well interval input sections are from surface down. When the check box is left empty in the
"show pore/fracture pressure," the program does not consider pore/fracture pressures.

In the calculation option frame, there are three options that will affect the results of the calculations.
The formulas for these calculations are discussed in Chapter 2 "Theory and Equations."

-
.­
6-13
 Pull-down the Customer Utility menu, select the wellbore option and the wellbore schematic will
be displayed on the screen (Figure 6-17).

Wellbore Schematic
flle Ip
llD lftl I
"Wei 11.D. (ft)
' . .'
I>
I'
' I
I
I
I
' '
I+'
I 0
..
''
I
I I I I I 0 I'

: : : : : : ::
llDI. -t-+-i-i­
'I' t
-~--~-~-~-
'I I I

l ~ j 1 ; ~ ; ;
...........
2000.
t

I
'I'
•

I
I
I
..........
. ' ' ' ____
o I

I
0

0
0
I

I
I
I

I
I
I

I
I
I ' ' ' 0 I I I

.
I I' I t I It
I Io o o I I I
I I I I 0 I I I
]000. ' .• .,.,.
r•T '' ' 'f""r'"
••,.-v ''
.. ' . ..
I
'
l
>I
I 0
''
I

'
I'
I I

. . ' .. '.
I I I I It 0 I
I I I o' 0 I

4000. -:-:
I

~-:- -·:·:-:-:­
. ' ' ....
I I 0 'I I

: : .: : : : :
51Dl. .........
'I
I Io
''.
I

___ ..
' .......
I
I
I
I
'
I
I
0
I

.
~
0 I I I I I I
'' 'I'' ' '
.. '' '' ''
I I
I
I
I
I
. I
I
I
I
0
I

. '. · . ''
I I I I I
'
I

6000. ·r-,.,.,. ·r·r·

.
'' I I I ''
I I I' 0 0 I
I It I I I I

I ''
I
I
I
I
'I
I
'>
0
O
0
'I 'I
'0
'I I> 0 '<
7000. :--:-­
I
'I...
-~-~-~-~- --}

.' '.
. . .'' ..
I ....
'' I 0

.. '. ' . '

I I I
0

I
I

I
I

<I
I
Welllore

7950. Quil
llodelSeled;;d._.:::==============================::'....::======:J

Figure 6-17. Wellbore Schematic

The wellbore graph is only available on the POI screen page.

6.5 SAVE INDMDUAL FILES

The user can save WDI, SDI, TOI, and POI files individually. While the POI page is on the screen pull­
down the File menu, the user can open/save the POI file to a diskette. It is the same as managing other input
pages.

6-14
-
-
-I Input- [Parameter Doto Input Window]
flle Model E!age Bun Cuatomer \lllllty Help
Mew Project c·~nYJt:UE5I te! P-5ol5
Qiien Project ...
s.~ Proj.,ct locet
Sa~ Proj1~cl As ... ....... Al Well 11.D.: Pole P.(paij 13000 IF•-=- P.1....1 151111 I
New Ale
Open Ale ••.
I r... I l.D. I Frie. I PoreP I frac. P
In-
I lftl I ro.i I I'"'"'' I lnait
SBYeAle 7.000 0.2111 2000 D-o
SBYe AleAa... 51111.0 6.000 0.300 1500 3500
frlnL.. Current Paqe I Clo•

E!dl I All Pages Data&......

I

- ,~Weight:~1-surt.,.Pr....,10:
_ l~•I I o.:m I _111!!!1
-surface E....._.. Dr-s
I !illll I
lc~..,o-:

1811-A&M '-king crilorio

[rubino Mo•iflo Sp...t.~ ISlulfing a.. Dr•1 II!!!! I 700
1811-... heicol lriclianol lorce
llltlhnl I ReolBal- 11>11
100.00 I
300 I
!Alculolian ­
lflowllolc ITube - incnt. ..... I 500.0 1811-... bm*1g · ­
IC.ae&.tion inl.-v. ,.., I 100.0
_I 1111!!!!1 I 10.00
1 I IM.D. af inte1eat l(ltl I 7950.0 I
11..iol Soloded: Drill

Figure 6-18. Manipulating with POI File

6.6 RUN

After examining all input files, select operation model and check the calculation options, then click Run
and Start to onset the calculation. There is an alerting window that displays on the screen while the program
is calculating.

6.7 OUTPUT WINDOW

When the calculation is finished, the program unloods the INPUT Wm.low anl displays the OUTPUT Wm.low.

"Child" windows are employed to display text reports, graphs for various calculation results. A "child"
window is a window confined to its "parent" window - the OUTPUT window. "Child" windows can be
displayed independently. The user can manipulate them just as normal windows: move, resize, close, etc. The
arrangement commands in the Window Menu (Cascade, Tile, Arrange Icons) have the same functions as those

­
.
of the Program Manager of Windows itself.

6-15
 There are six "child" windows within the OUTPUT Window. These windows display on the screen in
the file fonnat automatically. They are:
1. Equivalent Stress (static) - graph
2. Hydraulic Pressure (static) - graph
3. Axial Drag (static) - graph
4. Surface Load (dynamic) - graph
5. BHP (dynamic) - graph
6. CSTRESS Data Report - table

Use the mouse to click any of the "child" windows, then the "child" window becomes activated and the
title bar background color changes. Only one "child" window can be activated at a time. The CSTRESS Data
Report Window will show data for the graph in the active "child" window.

-I Output I· I; I
flle Window Help
H draullc Pressure tau
Equivalent Strrn Hydraulic Pressure Axial Drag
I - ---••­

,_ ,... ,..,.,
KJ).
1•1
I.....,
Mll.
1•1
'""
KD.
1•1 / ..
1­ 1­
I,,.,.
-. '
,,_.()sq
• • I rw.
-~
1 ...

Surface Load BHP

Surface Load
.---------­ ,_ s1r...
@7950.0
1 0.0
2 100.0
KD I""'' Mll. 3 200.0
(kl 1•1 4 Dl_O 300.0
1­ 5 .eoo.o 400.0
/!"""< & 500.0 500.0
lop
I rw. 7 600.0 600.0
8 700.0 700.0 +
S&#l.a.ofl.oaod[MJ Bol:.lol•PNUW•(J.Al + •

Figure 6-19. Output "Child" Window

6.7.1 Print Results

To send results to the printer: I) activate the desired "child" window, 2) pull-down the File
menu, and 3) click "Print Report/Graph Only."

6-16
-
- -I
Elle Wlndaw Graph Qptlon
Output
.tielp
I· I~ I
I
l!Tlnt Report/Graph only
Print Profect flle
Print WI and SDI Ale
Print IOI and POI File
!;opy Graph lo Clipboard
Ji""" Report o;sk File
Bade lo Input
fxll

Figure 6-20. Pull-Down File Menu

The user can print the input data by selecting "Print Project File," "Print WDI and SDI File,"
and "Print TDI and PDI File." If "Save Report Disk File," is selected, the data in the CSTRESS Data Report
"child" window with/without TDI and PDI data will save to diskette.

Copying the active graph to the clipboard can put the graph image to clipboard, and this graph image can
be retrieved by certain window graphic programs, such as Window-Paintbrush.

6.7.2 Manioulating the Outout Graph

Under Graph Options - Image File Fonnat pull-<lown menu there are two types of graphic file
formats: Bitmap and Metafile.

-I Output
Elle Window Groph Qptlon · l:lelp

.­

Figure 6-21. Graphic Image File Format Selection

One difference between Bitmap and Metafile is that Metafile is resizeable. After selecting Metafile
and copy graph image to clipboard, open Windows Utility: Clipboard Viewer and change the size of the Viewer
window. Graph size proportions itself to the window size.

To enlarge the size of the graph in the OUTPUT Window:

.- 1. Activate the sub-window by clicking any where inside the window (the title bar of active sub­
window is in color).

6-17
 2. When the mouse cursor is moved to the boundary of the sub-windows, 1he cursor becomes
a double arrow (Figure 6-22).
3. Hold left button of mouse, then drag the boundary to the siz.e you want.
4. For a full-screen graph, click the maximiz.e box in the top-right corner of 1he sub-window.

NOTE: It is impoTtant to change the size of the graph on the screen because the size of the
prinled graph depends on the size of the graph on the screen.

=I Output
flle

M.D.
(fl) ...

...
/ ......
M.D.
(fl) -
-
Axial Load(lbf)
I""
llol loi. P1HN"• (Jd}

Figure 6-22. Change Graph Siz.e

If the user selects Window - Cascade from the pull-down menu, the "child" window (only the
visible "child" window) in the OUTPUT Window becomes CASCADE.

6-18
 -I Output l·I:
file Window Graph Qpllon l:!•lp
BHP IDvnomlcl I
Surface Load lnvnamld I
kdol Droo !Stolle) I
"""roullc Pressure !Statlcl I
Eaulv. Stra. !Stadel I
-I Data Report I· I&
E--..
Stress
MUIU'ed IV•tieal
Doolh 10­
10­ ....
I IStresa
IEnuiv. IAxiol
IStress
•
I @7950.0 ftl llftl lrD/10Cltl llDlil llDsil
1 0.0 0.0 0.00 7754 5747
2 100.0 100.0 0.00 7595 5305
J 200.0 200.0 0.00 7461 4871
4 300.0 lDD.O 0.00 7350 4443
5 400.0 400.0 0.00 7265 4023
6 500.0 500.0 D.00 7204 l6D8

-- 8
7 600.0
700.0
600.0
7DD.O
0.00
0.00
7167
7153
32111
2797

-.... ....
9 800.0 800.0 0.00 7162 2399
10 900.0 900.0 0.00 7193 2006
11 1000.0 1000.0 0.00 n46 1618

..
12

•I I
1100.0
n
·-·
1100.0 0.00
n nn
7318
--­ ... 1234

I+
-
•

Figure 6-23_ "Child" Window CASCADE

6.7.3 Select Outuut Graoh Curves

-
. When the calculation is finished, all output graphs with whole set curves will display on screen .
Not every curve is important to the user, so the program provides the option of presenting the desired curve on
the graph. Select Graph Option - Curve Option pull-down menu, CSTRESS's Graphic Curve setting will
display on the screen.

Equivalent Stiess Hydraulic Pressure Axial Drag

...
Equjyolonl s-. H,m..........e - Lo+d (8...,.) S..toce Lo+d Botta• H• Pre.

t&'.ll['!!!!.. 51••-il C8:J hllemal Pre. C!lJ S-0 (Log. I C!lJ Hook Lo+d iZl Bal. Hole Pro.
IZl-sb... 181 ......... Pr•. 181 Yield Load t8J T-g Top t8:J Pme Pie.
181Y...d Sh... 181 POfe Pre. t8J Sinu..,;d BU ~ F1acture Pie.
18:1 Ftactwe Pre.. 181He&c.IBU

K.D.
1•1
~ 181 Somo Bltl..

/ t•bbc 6 500.0 !illl.O

lop
/rw. 1 600.0 600.0
e 7DD.O 700.0 +
SWlacitl.Gld (llE) S:.:. lail• P1•11ft.. (Jlsil
• •

Figure 6-24. Graph Option - Curve Option Pull-Down Menu

6-19
 Choose the desired curve by clicking the mouse at each check box (mark an x in each box), then
click the OK button and the program redraws each graph.

6.7.4 Bi-Axial Grauh

To examine the bi-axial and API stress for each coiled-tubing section, pull-down the window menu
and select Bi-Axial Graph. The Bi-Axial stress graph displays on the screen.

Output ;
Elle

Minimum Yield Pressure

Ptes111te (kli) Bi-axial nnd API Grnph
20..-....---..-.--....--.-~~-T-~~~
BURST Slri_!!!!_Dl!!Un
16 @11o1 -:39001
0 i;i"ii00:1soo
12 0 Jtd
0 4th
• 05th
06th
4
01th
--j.-Aoiol 0 r---t---.----,........,--~-->'--'
____,.,., 0 Blh
09lh
-... 4 0·111111
DD-1.!ilq"oo)
8
ID- 1.232(;,,I
12 T--- 0.1341;,,1
E• 30000000bml
16 Y-BOOOO(pal
IDLL\PSE

.. •

Figure 6-25. Bi-Axial API Stress

Depending on TDI input, the right-hand side of the program lets the user examine each input CT
string section. NOTE: the TDI input program allows up to fifteen strings but only allows ten strings in this
window. The numbers printed to the right of the string order number is the measure depth range of each section
and shows string information at the bottom.

Although the program shows triaxial stress calculation results on the Equivalent Stress (static) graph
and in the CSTRESS Data Report, the biaxial stress criteria is still required here to draw the ellipse. The upper
part of the ellipse is based on zero outside pressure and the lower part of the ellipse is based on zero inside
pressure. The pressure data used to draw the inherited pressure-stress curve for each pipe section, are the
difference between inside and outside pressure. If the inside pressure is greater than the outside pressure, the
program uses the pressure difference to check the pipe in burst consideration. If the inside pressure is less than
the outside pressure, the program uses the pressure difference to check the pipe in collapse consideration. For
example, if the outside pressure is 4000 psi and the inside pressure is 1500 psi, the program uses 3000 psi ( =
4000 - 1000) outside pressure and zero inside pressure to draw the pipe curve and the user can examine the
biaxial and API stress in collapse. In Figure 6-24, the curve of the pipe is inside the curve of the biaxial and
API which implies the pipe inherited stress is less than the yield stress.

6-20
- 6.7.5 Pumo Equipment
The tubing pressure data shown in the graph and output report are for coiled tubing that is inside
the wellbore (i.e., below the BOP). For coiled-tubing operation, the mud pump is connected to the reel. Certain
lengths of coiled tubing remain on the reel. When mud is pumped through the coiled tubing remaining on the
reel, there is extra pressure loss on this section of the tubing. To calculate pressure loss and find the required
output pressure and horsepower of the pump, pull-down the window menu and select PUMP EQUIPMENT.
The PUMP EQUIPMENT Window displays on the screen.

-I
file

x.n.
(It) CT l - ' > in Halo ~II
In. CT ,..._ .. BOP (pail
NwlWlrighti-J
Tubing ID r"'I
J1!i000
j1350.o
j2695
j10.111
11.2511
r-··
I
c:T length on nool llll • 1050.0
CT Pt.a. Lon on 1eel l""iJ
P,., Dulpul l'leL (pli) • 4536
• 1841

llequired P,., HP (HHP) • 117.6

Plmtio v.._il, 1...1 j12.0

Yield Point 1•1'1 OOll2) j5.lll c.........
Fbw Hale [gpm) Ioo.oo
Pu•p EfficiMctt j.9 60 Back
0 Pawerl.., ® Binghmo platic
K.n
(It)

1lop
­
--. '
/""­
6
1
8
500.0
6111.0
100.0
500.0
6111.0
100.0 +
Bot.llMPIHM•(Jd:i)
• •
Figure 6-26. Pump Equipment Window

Most input data for the PUMP EQUIPMENT Window comes from previous input and output data.
The user can edit any of the input data. After the input data are satisfied, click the calculate button and the
output data is shown on the screen. Click the go back button and the PUMP EQUIPMENT Window is closed.

6.7.6 Exit Output Window

To leave the OUTPUT Window, pull-down the File menu, select "Back to Input." This takes the
user rack 1o 1he INPUT Wmdow k> edit inp.rt dala, select "Exit" This exits 1he program and goes rack 1o MS Wmlows.

6-21
6.8 USING TORTUOSITY

When the Survey Data Input (SDI) page is loaded into the INPUT Window and the survey data has been
created, click the tortuosity command button and the TORTUOSITY Window displays on the screen.

-I Input - fSurvey Data Input WindowJ l·I:

[lie Model Page Bun Customer !J.tility l:!•lp
C·\VR\CH\TEST SDI P-3 ol 5

Unit 1:2!JYl;!ll"!i:!!J ~ ~
Qm!Jti
IDCJtn•I~
e.nsn --.
iYim!!!!l

.-Dcpth;­ 1
2
0.0 0.00 0.00 ..
@Feet 100.0 0.00 0.00 f­
3 •oo.o 0.00 0.00
Owntm
•
5
800.0
1200.0
0.00
0.00
0.00
0.00
r-1nclina4ion: ­ 6 1600.0 0.00 0.00
@ Dcciowtl
7 200tl.O 0.00 0.00
B 2400.0 0.00 0.00
oo... w;,, 9 2800.0 0.00 0.00
10 3200.0 10.00 0.00 +

-~::1 [E~I
I
insert Line licicte lb:

0 Di FIOld I TortuozilJ...
I

Figure 6-27. Tortuosity Command Button

Tortuoslty
Survey Delo Tortuosity Doalea
Otininn..I Meaured llnclinelion IA.znulh ID•
o- 1-~
1· - ·
IS Dogleg Severity
Station feel I I II

~6
1 0.0 0.00 0.00 I
2 100.0 0.00 0.00 I
3 400.0 0.00 0.00 I M.D. / tolfad.

4 800.0 0.00 0.00 I (ft)

5 1200.0 0.00 0.00 :I
6 1600.0 0.00 0.00 I I e>;p>"'
aa
·~•
1 2000.0 0.00 0.00 OD Oj 1,0 Jj ZJ 3.D

+I
- ·-- --
I+ DogleglD/!Ollfl)

N.........1z-11105J: LI SDI Fila N-C:\YB\CH\TEST .SOI

BollonlllD Allpliludo Period IMelt Stetions Sia. Inter. Len.
Zone 1: IJOOo 111 11500 I 1811.... Flag 1 1100 I
Zone 2: 1&000 112 11 500 I 1811n1. Flog 2 1100 I
Zone 3: leooo 113 11 500 llZli!!i•T~ 1100 I
Zone If:
Zone 5:

I Calculate I I U.-Do
I I Prft <F6> I I OK I I
C.....t
I

Figure 6-28. Tortuosity Window

6-22
.- At the top of the TORTUOSITY Window, there are two "child" windows:
2) Tortuosity Dogleg Graph. At the bottom of the TORTUOSITY Window is the data input area.
1) Survey Data Table and

The survey can be divided into as many as five zones (for example: surface to KOP, first build section,
first tangent section, second build section, and second tangent section). Each survey zone may then be given
a different amplitude for its distributed tortuosity. The bottom measured depth is always equal to the maximum
survey depth. The period data is the length of one sine wave cycle. The user can input the desired tortuosity
cycle. Sometime the survey data density is low and the user can click insert stations and the program imer1S more
stations between the l\\Q original sur.ey slations. The defuult imert slation interval 1ength is 100 ft.

-I Tortuo11ty .
Survey Data Tortuositv Do oleo
TDll••d Meaured llnclinMian lluftul:h II +
D­ 1­ 1~. IS Dogleg Severity
SYiion leot I I I~

·~ ,.......
1 0.0 0.00 0.00
2 100.0 0.95 8.95 I -2000
3 20Q.O 0.59 0.59 I
111.0.
(ft) -.lOOO
4 300.0 0.59 119.41
5 400.0 0.!15 179.115 :I "'000
6 500.0 0.00 0.00 I
.,lODOO 2 ~ 6 8 I °""'""
•I
7 &oo.O
·­
0.95
·-·­ -·­0.95
I•
•
I­
Oogleg(O/I DOit)

-··•z-111o5):

z-1:
Z-2:
z-J:
Bottc. MD

IJOOo
1&000
leooo
-
Li
111
11 2
IIJ
SDI Filo N-:1::\VB\CH\TEST.SDI
p­
11500
11500
I1500
1,..1 Slllliofta

I 1811no. fllla 2
I 1811... flllg J
Sia. Int•. Lal.

I 1811.... flllg 1 l•oo

1100
1100
I
I
I
Z-4:
Z-5:

I Celculole I I
UnDa
I I Pm <FG> I I OK I I
c.n.el
I

Figure 6-29. Tortured Survey

There are five command buttons at the bottom:

1. Calculate - tortures the original wellpath, and both the survey data table and dogleg severity graph
shows the tortured survey.
2. Un-Do - resets the data to the original survey data.
3. Print <F6> - prints the active window. If a table or graph is displayed on the screen and the
print command button cannot be seen, press the < F6 > function key to execute the print
command.
4. OK - copies the tortured survey data to the SDI file in the SDI Input screen.
5. Cancel - leaves the TORTUOSITY Window without any changes in the SDI data.
Both tables and graphs can be enlarged.

6-23
 -I Tortuoally .
Su"J'll'V Data -1 Tortuoaitv Doalea I• l..t.
Todured Measured lncinalion IAznuth II +
Slalion
1
D­
feel
0.0
·­
0.00
1 ·-·
I
0.00
IS
IJ
Dogleg Severity
2 100.0 0.95 0.95 I 0 -------------­
3
4
200.0
Dl.O
0.59
0.59
0.59
119.41
I
I:• •
5 400.0 0.95 119.05 I Iii•
-2000 I.Ii.
6 !illl.0 0.00 0.00 I
7
8
9
60D.O
700.0
....o
0.95
0.59
0.59
0.95
0.59
119.41
J
I

. .
I;>
, .......____
/ lod-t.
'--­
10
11
900.0
lDOO.O
0.95
0.00
119.05
0.00
I
I DI
M.D.
(ft) -lOOO
...... '---'
12 1100.0 0.95 0.95 I o[ '---'
t:::::::::I
"'
~
13 1200.0 0.59 0.59
14 l:Dl.O 0.59 119.41 .
I
~

I
::::::::i

--
15 1400.0 0.95 119.05 ·1
~ODO
16 1500.0 0.00 0.00 I
17 1600.0 0.95 0.95 I
/"""'""
18
19
20
1700.0
1800.0
1900.0
0.59
0.59
0.95
0.59
119.41
119.05
I
1
I -.!1000
"'= ­ . '

21 2000.0 0.00 0.00 0 2 4 i 8

-~
22 2100.0 0.95 0.95 I • < DoglogtD/IDOft)
•I I I•

Figure 6-30. Tortured Survey Data and Dogleg Graph

6.9 CSTRESS HELP AND DIALOG BOXES

There are five types of dialog boxes associated with menus: Assistance dialog box, About dialog box, File
Open dialog box, File Save dialog box, and Color dialog box.

6.9.1 Helo - Assistance...

When the user selects the "Assistance... " command from the Help menu in both INPUT and
OUTPUT Windows, the following dialog box appears (Figure 6-31):

-I Assistance

For assistance with this program. contact:

lee Chu
or
Gefei Liu

Maurer Engineering Inc.

2916 West T.C. Jester
Houston. 1X. 77018
LI.SA

Phone: 713-683-BZZ7
Fax: 71J-68H418
Telex: 216556

Figure 6-31. Help - Assistance Dialog Box

6-24
 6.9.2 Help - About...
When the user selects the ''About. .. '' command from the Help menu in both INPUT and OUTPUT
Windows, the following dialog box appears (Figure 6-32):

-1 : About Cstress

Cgjled Jybjpg Stress AnahPs Mglcl IC$trml \:.O~ ::j

Afmlign 1 QI

Ptojod to Dnelop-
.,
DEA-U
EY-• Slim-Hole­
Coilod-T.-.a r-...
. . . . . Eng._.iftg lllC.

\II- CPU : lnlel 111486

Caprocesaor : pn1..,..
Mode: Eohmcod llodo
W-lrldolnVenion: 31.10
Free Me•ary : 1711D KB

Figure 6-32. Help - About Dialog Box

6.9.3 Ooen Project and Data File

When the user selects the "Open Project" or "Open File" from the File menu in the INPUT
Window, the following Open dialog box appears (Figure 6-33):

-I Open CDRRle
11.ireotorin:
D"
c:\vbld>
c.nc.1
i...~cct.....
teMO.alr
-I.air
lmt2.cdr
-3.alr
t..t4.cdt
tnl!i.alr
teot6.c:do
li•t Fin of !Jpe: D1ivea:
r-".co-"-R"''-----'l"'"'t
"-I I j e c: 1eo..,., &&
Figure 6-33. "Open Project" Dialog Box

This dialog box enables the user to search the file system for the desired files with the extension
".CDR." The extension name (.CDR, .WDI, .SDI, .CT4, .CP4, .DB, etc.) is chosen automatically by the
program to determine the type of file that will be opened in the different windows.

The user can move between sections of the dialog box by simply clicking on the desired section.

- Alternatively, the user can press the <TAB> key from keyboard until the focus moves to the desired section.

6-25
 There are four list boxes: the drive list box, the directory list box, the file list box, and type list
box. Their :fuocliom are descnbed below. There is ore 1eXt box am Mi COllll1lllld buUorl;: OK am CANCFL.

1. The Drive List Box

On the lower right corner is the drop-down drive list box. In its normal state, it displays the
current drive. When the user clicks the arrow at the right of the drive list box, it drops to list
all valid drives. The user can activate a new drive by single-clicking the desired one.

2. The Directory List Box

The directory list box displays the hierarchy of paths of the current drive. The current
directory appears as a shaded, open-file folder; directions above it in the hierarchy appear as
a nonshaded open-file folder, and those immediately beneath the current directory are closed­
file folders. The user can change the directory by double-clicking the selected one. Note that
in the directory list box, a single click only selects (highlights) the item; a double click is
required for the command to be perfonned.

3. The File List Box

The file list box displays the files in the current directory. The file names shown are those
specified by their extension name ''CDR.'' A single mouse click on an item makes it appear
in the "File Name" text box. If the user chooses OK at this time, the data file is retrieved
and all data related to the current calculation mode are displayed in appropriate entries.
Double-clicking the selected file has the same effect as above.

When the user selects a new drive, the directory list box is updated, which then causes the
file list box contents to be updated. When a new directory is selected, the file list box is
updated, but the drive remains the same.

The path specification label always represents the current path information.

4. The Type List Box

This list box is set by the program. The user cannot change it. It specifies the type of files
that are to be displayed in the file list box. In this "Open Project.." dialog box, the type of
file is "*.CDR."

5. "File Name" Text Box

The application should also do the following when the user enters text in the "File Name"
text box and then presses < ENTER > .
• If a drive letter is entered, 1he drive, directory' am file list boxes shook! be updated.
• If a directory path is entered (for example, "\CSTRESS"), the directory list box
and the file list box should be updated accordingly.
• If the name of an existing file (with extension name ".CDR") is entered, the
dialog will be completed and the files will be retrieved.

6-26
-
- 6. Command Buttons
If the existing file name is shown in the text box, pressing OK will complete the dialog and
the data file will be retrieved and displayed.

If the CANCEL button is pressed, the dialog is cancelled and no information is made
available to the application.

6.9.4 Save Project - Data File

When the user selects "Save Project As" or "Save File As" commands form the File menu in
the INPUT and OUTPUT Windows, the following dialog box appears (Figure 6-34):
-I Se"" SDI Fiie A.& •••
File ti.-..: liireclarin: 01:.
\c:\Yb\ch\lul.adi c:\Yb\ch
tml~
c:.nc.1
tm1.0.~1
te\'C.1.;t.1.li
ltrS'l2 . .uli
IB<t7 ..uli
tm'9."di
-
S.we File u !fpe: Drives:
\1·.so11 I! I I
~J1!!!~--c:-1oe-.,.,-66--J,.....,t

Figure 6-34. "Save File" Dialog Box

This dialog box is almost identical to the "Open Project" dialog box in appearance; however, the
.- filter in the type list box is different. Depending on the file the user is manipulating, the filter in the type list
box will be a ".CDR," ".WDI," ".SDI," ".CD4," or ".DB," etc., extension.

6.9.S ~

When the user selects one of the commands on color from the Customer Utility menu in the
INPUT Window, the following dialog box appears.

-1

D
C,uato111 Colorr.

DDEJE!Elf§J~~ !iue:[160 I B.ect:l255 I.

~ GJ ~ 1111111 • • • • 1a1: Li li•-= J255 I
I Qolinc Cwlo,. Colo«... I Cola1IS2fid !..•m: ~ 12551
Bil!"'

:::,=o=K==;;;-1-;:1=_~Cane=
. =.=,=:"11=_=H.=lp===il ""'= =-=--""'~'-"'d_d~t-•_eu._1a111=· •-lo=rs==.....,il
c_·

- Figure 6-35. Color Dialog Box

The Color dialog allows the user to select a color from a palette or to create and select up to
sixteen custom colors.

6-27
6.10 CSTRESS ERROR HANDLING

When input data on a page are outside the appropriate range of values and the user tries to leave the page,
the CSTRESS error checking routines will locate the error. The application will then display an error message
explaining why the data are not acceptable. The user can ignore the error message and leave the page even
though the data on the page do not make sense. This enables the user to edit and view different input pages
without having to complete one before going to another.

The user can start calculation from any page. If any invalid data are found at this time, the application
will display an error message and force the use to go to the page with invalid data for editing.

When an error message appears, click OK or press <ENTER> to return to the associated page in the
INPUT Window.

6.11 QUICK START

Use the following procedure to get started with the CSTRESSl program.

Install:
1. Start Windows (3.0 or later version).
2. Insert Disk into drive A:.
3. In the File Manager, choose Run from the File menu.
4. Type A:setup and press Enter.
5. Follow on-screen instructions. (Please use the default subdirectory).

Run:

6. Double-click the CSTRESSl icon.

7. In the first window (INTRODUCTORY Window), click "Continue" after it becomes responsive.
8. In the INPUT Window, choose "Open Project. .. " from the File menu.
9. From the "Open CDR File" dialog box, click the drive C: in the drive list box, double-click the
"CSTRESS" subdirectory, click the "TEST.CDR" in the tile list box, and then click OK.
10. Click "Next" from the Page menu to view other pages of input data (WDI, SDI, TDI, PDI).
11. Click the "Start" from the Run menu. After calculation the OUTPUT Window is loaded.
12. In the OUTPUT Window that follows, select the text report or interested graph windows under the
"Window" and "Graph" options of the menu to view the output.
13. To print the text report or graph, make the corresponding "child" window active, select "Print
Report/Graph Only" from the File menu.
14. Choose "Back to Input" from File menu to return to the INPUT Window or choose "Exit" to
terminate the application.

6-28
-
- 7. References

1. Bourgoyne, A.T., Jr., et al.,: Applied Drilling Engineering, Richardson, Texas, Society of Petroleum
Engineers.

2. Specification for Materials and Testing for Well Cements API SPECIFICATION 10 (SPEC 10) FIFTH
EDITION, JULY l, 1990.

3. Leitao, H.C.F. et al., 1990: "General Computerized Well Control Kill Sheet for Drilling Operations with
Graphical Display Capabilities," SPE 20327 presented at the Fifth SPE Petroleum Computer Conference
held in Denver, Colorado, June 25-28.

4. Security Drill String Systems: Hydraulics Manual.

5. Moore, Preston, 1974: Drilling Practices Manual, The Petroleum Publishing Company, Tulsa. Oklahoma.

6. Dawson, Rapier and Paslay, P.R., 1984: "Drillpipe Buckling in Inclined Holes," Journal of Petroleum
Tecluwlogy, October.

- - 7. Chen, Y.C., Lin, Y.H. and Cheatham, J.B., 1989: "An Analysis of Tubing and Casing Buckling in
Horizontal Wells," OTC 6037, 21st Annual OTC, Houston, Texas, May 1-4.

8. Lohuis, G. et al., 1991: "Coiled Tubing/Production Logging in Highly Deviated and Horizontal
Wellbores," CIM/AOSTRA 91-15, 1991 CIM/AOSTRA Conference, Banff, April 23-24.

9. Newman, Kenneth R., Corrigan, Mark and Cheatham, John B, Jr., 1989: "Safely Exceeding the 'Critical
Buckling Load' in Highly Deviated Holes," SPE 19229, Offshore Europe '89, Aberdeen, September 5-8.

10. Spotts, M.F., "Design of Machine Elements," Prentice-Hall, Inc., Englewood Cliffs, N.J.

11. Wahl, A.M., 1963: "Mechanical Springs," 2nd Ed., McGraw-Hill Book Company, New York.

12. Wu, Jiang and Juvkam-Wold, Hans C., 1993: "Preventing Helical Buckling of Pipes in Extended Reach
and Horizontal Wells," Energy-Sources Conference & Exhibition, January 31-February 4.

13. Wu, Jiang and Juvkam-Wold, Hans C., 1993: "Frictional Drag Analysis for Helically Buckled Pipes in
Extended Reach and Horizontal Wells,'' Energy-Sources Conference & Exhibition, January 31-February 4.

14. API Bulletin, 5C3, 1989: "Formulas and Calculations For Casing, Tubing, Drill Pipe and Line Pipe
Properties."

7-1
- 8. BUG Report or Enhancement Suggestion Form

- Name: Company:
Addr~: City: State: _ _ __
Phone No.: Fax No.: Date:
D Bug\Problem Report D Enhancement Suggestion

Program Name and Version Number:

Bug\Problem Description or Enhancement Suggestion:

Regarding the Bug Report, please answer the following questions:

Computer System Brand:
---------
Chip: 0 286 D 386 D 486 D Pentium
Type: D Desktop D Laptop D Notebook D Other

- - Printer Type:
RAM: MB
Math-Coprocessor Present:
Sw!l:
D Yes
MHz
D No
(for printing error only)
D Unknown

Plotter: (for plotting error only)

Within Network System: D Yes D No Type:
Video Type: D EGA D VGA D SVGA D Mono D LCD
Video Card Ram: _ _ _ _ _ _ _ (video problem only)
Operating Svstem
MS-DOS Version No.: - - - - MS-Windows Version No.: _ _ _ _ (forWindowsapplications)
OS2 MS-Windows NT Version No.: - - - -
----------
0ther
----------
BUG Detecting Data
[] Will be mailed on diskette D Will be faxed D Attached D None
Other Comments:

- Please send or fax to:

Lee Chu
MAURER ENGINEERING INC.
2916 West T.C. Jester
Houston, TX 77018-7098
Ph.: 713/683-8227 • Fax: 713/683-6418
8-2