Introduction to Well Testing
Table of Contents
Introduction to Well Testing (March 1998)
TOC - 2
Schlumberger
Section 1.0
Basic Reservoir Engineering
1.1
Introduction (Course Objectives).............................................................................. 1-3
1.2
History
..................................................................................................... 1-3
1.3
Geology Recap
..................................................................................................... 1-4
1.3.1
1.3.2
1.3.3
1.3.4
1.4
Rock Classification.....................................................................................................................................1-4
Rock Properties.............................................................................................................................................1-5
1.3.2.1
Porosity........................................................................................................................................1-6
1.3.2.2
Permeability..............................................................................................................................1-7
Hydrocarbon Accumulations...................................................................................................................1-8
1.3.3.1
Domes And Anticlines.........................................................................................................1-9
1.3.3.2
Salt Domes And Plug Structures.................................................................................. 1-10
1.3.3.3
Faults......................................................................................................................................... 1-10
1.3.3.4
Unconformity .........................................................................................................................1-11
1.3.3.5
Lenticular Reservoirs......................................................................................................... 1-11
Reservoir Temperature And Pressure.............................................................................................. 1-12
1.3.4.1
Normal Pressure...................................................................................................................1-12
1.3.4.2
Abnormal Pressures............................................................................................................ 1-13
1.3.4.3
Reservoir Temperature...................................................................................................... 1-13
Interacting Forces, Saturation And Displacement....................................................1-13
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
General ......................................................................................................................................................1-13
Surface And Interfacial Tension ........................................................................................................ 1-13
Wetting ......................................................................................................................................................1-14
Capillarity.....................................................................................................................................................1-15
Saturation...............................................................................................................................................................
1.4.6
1.4.7
1.4.8
Irreducible Water Saturation............................................................................................................... 1-16
Residual Oil.................................................................................................................................................1-16
Relations Between Permeability And Fluid Saturation ......................................................... 1-19
1-15
1.5
Fluid Properties ....................................................................................................1-21
1.5.1
1.5.2
1.5.3
1.6
Components Of Hydrocarbon............................................................................................................... 1-21
Classification Of Hydrocarbons.......................................................................................................... 1-23
Characteristics Of Formation Water................................................................................................ 1-25
Phase Behaviour ....................................................................................................1-25
1.6.1
1.6.2
1.6.3
1.6.4
1.6.5
1.6.6
Phase Behaviour Of A Single Component System................................................................... 1-25
Phase Behaviour Of A Multi-Component System..................................................................... 1-27
Reservoir And Fluid Compressibility .............................................................................................. 1-28
Conversion Factors Between Surface And Downhole Volumes.........................................1-28
1.6.4.1
Formation Volume Factor Of Gas, Bg ...................................................................... 1-29
1.6.4.2
Formation Volume Factor Of Oil, Bo........................................................................ 1-30
1.6.4.3
Formation Volume Factor Of Water, Bw ................................................................ 1-31
Fluid Density Corrections .....................................................................................................................1-31
1.6.5.1
Gas Density............................................................................................................................ 1-31
1.6.5.2
Oil Density.............................................................................................................................. 1-31
1.6.5.3
Water Density .......................................................................................................................1-32
Viscosities ....................................................................................................................................................1-32
1.6.6.1
Gas Viscosity.........................................................................................................................1-32
1.6.6.2
Oil Viscosity..........................................................................................................................1-32
1.6.6.3
Water Viscosity....................................................................................................................1-32
1.6.6.4
Formation Compressibility.............................................................................................. 1-32
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Table of Contents
1.7
Reservoir Drive Mechanisms .................................................................................1-32
1.7.1
1.7.2
1.7.3
1.7.4
1.7.5
Section 2.0
Oil Reservoirs ............................................................................................................................................. 1-32
Solution Gas Drive Reservoirs............................................................................................................ 1-33
Gas Cap Expansion Drive Reservoirs.............................................................................................. 1-35
Water Drive Reservoirs..........................................................................................................................1-36
Discussion Of Recovery Efficiency.................................................................................................. 1-39
Completion Technology And Types
2.1
Introduction
2.2
Completion Components...........................................................................................2-3
2.2.1
2.2.2
2.2.3
2.2.4
2.2.5
2.2.6
2.3
Section 3.0
Natural Completions................................................................................................................................ 2-18
Stimulated Completions ........................................................................................................................2-18
2.4.2.1
Hydraulic Fracturing.......................................................................................................... 2-18
2.4.2.2
Acidizing................................................................................................................................. 2-19
2.4.2.3
Extreme Overbalance Perforating................................................................................ 2-20
Practical Well Testing
Introduction
3.1.1
3.1.2
3.2
General ......................................................................................................................................................2-16
2.3.1.1
Open Hole Completions ................................................................................................... 2-16
2.3.1.2
Cased Hole Completions ................................................................................................. 2-16
Completion Types .................................................................................................. 2-16
2.4.1
2.4.2
3.1
Production Tubulars ....................................................................................................................................2-5
Packers .........................................................................................................................................................2-5
2.2.2.1
Permanent Packers................................................................................................................2-5
2.2.2.2
Retrievable Packer ................................................................................................................2-7
Flow Control...................................................................................................................................................2-8
2.2.3.1
Landing Nipples......................................................................................................................2-8
2.2.3.2
Sliding Side Door................................................................................................................2-10
Subsurface Safety Systems..................................................................................................................2-12
2.2.4.1
Subsurface Controlled Subsurface Safety Valves................................................2-12
2.2.4.2
Surface Controlled Subsurface Safety Valves....................................................... 2-12
Ancillary Components............................................................................................................................ 2-14
2.2.5.1
Wireline Entry Guide......................................................................................................... 2-14
2.2.5.2
Blast Joint ...............................................................................................................................2-14
2.2.5.3
Flow Couplings.....................................................................................................................2-14
General ......................................................................................................................................................2-14
Completion Techniques..........................................................................................2-16
2.3.1
2.4
......................................................................................................2-3
......................................................................................................3-3
Productivity Well Testing........................................................................................................................3-3
Descriptive Well Testing.........................................................................................................................3-5
Test Design
......................................................................................................3-7
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3.3
Tubing Conveyed Perforating - TCP........................................................................3-11
3.3.1
3.3.2
3.3.3
3.3.4
3.3.5
3.4
Drill Stem Testing Tools - DST................................................................................3-19
3.4.1
3.4.2
3.4.3
3.4.4
3.5
General ......................................................................................................................................................3-19
Basic Requirements................................................................................................................................. 3-19
3.4.2.1
Packer....................................................................................................................................... 3-19
3.4.2.2
Test Valve...............................................................................................................................3-19
3.4.2.3
Reverse Circulation Valve.............................................................................................. 3-19
3.4.2.4
Slip Joint.................................................................................................................................. 3-19
3.4.2.5
Hydraulic Jar..........................................................................................................................3-20
3.4.2.6
Safety Joint............................................................................................................................. 3-20
3.4.2.7
Safety Valve..........................................................................................................................3-20
3.4.2.8
Gauge Carrier ........................................................................................................................3-20
3.4.2.9
Sampling Chamber Tool .................................................................................................. 3-20
Types Of Drill Stem Tests....................................................................................................................3-27
3.4.3.1
Open Hole Drill Stem Testing....................................................................................... 3-27
3.4.3.2
Cased Hole Drill Stem Testing..................................................................................... 3-28
New Technology........................................................................................................................................ 3-32
Subsurface Safety Systems......................................................................................3-34
3.5.1
3.6
General ......................................................................................................................................................3-11
3.3.1.1
Through Tubing Perforating............................................................................................ 3-11
3.3.1.2
Casing Gun And High Shot Density Perforating (HSD)................................... 3-13
Benefits Of TCP ........................................................................................................................................ 3-13
Equipment Selection...............................................................................................................................3-15
Testing Requirements............................................................................................................................. 3-15
Firing Heads................................................................................................................................................3-17
3.3.5.1
Differential Pressure Firing Head................................................................................ 3-17
3.3.5.2
Hydraulic Delay Firing Head......................................................................................... 3-17
3.3.5.3
Bar Hydrostatic Firing Head.......................................................................................... 3-17
3.3.5.4
Trigger Charge Firing System ....................................................................................... 3-17
3.3.5.5
Redundant Firing Systems .............................................................................................. 3-19
General ......................................................................................................................................................3-34
Surface Testing Equipment ....................................................................................3-35
3.6.1
3.6.2
General ......................................................................................................................................................3-35
Equipment.....................................................................................................................................................3-35
3.6.2.1
Flowhead ................................................................................................................................. 3-35
3.6.2.2
Choke Manifold....................................................................................................................3-37
3.6.2.3
Heater / Steam Exchanger.............................................................................................. 3-38
3.6.2.4
Test Separator.......................................................................................................................3-38
3.6.2.5
Gauge Tank............................................................................................................................ 3-39
3.6.2.6
Pumps And Manifolds ....................................................................................................... 3-39
3.6.2.7
Burners...................................................................................................................................... 3-39
3.6.2.8
Emergency Shut Down Systems................................................................................... 3-39
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Table of Contents
3.7
Data Acquisition .................................................................................................... 3-42
3.7.1
3.7.2
3.7.3
3.7.4
3.7.5
3.7.6
3.7.7
3.8
Special Applications............................................................................................... 3-55
3.8.1
3.8.2
Section 4.0
4.1
Sampling Procedures Design ....................................................................................4-3
Samples Representivity ............................................................................................................................4-3
Producing Conditions.................................................................................................................................4-4
Well Conditioning.......................................................................................................................................4-5
Hydrocarbon Sampling Methods...........................................................................................................4-6
4.1.4.1
Bottom Hole Sampling........................................................................................................4-6
4.1.4.2
Surface Sampling...................................................................................................................4-6
Sampling Of Oil Reservoirs......................................................................................4-7
4.2.1
4.3
High Pressure High Temperature - HPHT..................................................................................... 3-55
High Flow Rates........................................................................................................................................ 3-55
Sampling Of Reservoir Fluids
4.1.1
4.1.2
4.1.3
4.1.4
4.2
General ......................................................................................................................................................3-42
Transducer Performance........................................................................................................................3-42
3.7.2.1
Static Parameters ................................................................................................................3-42
3.7.2.2
Dynamic Parameters.......................................................................................................... 3-45
3.7.2.3
Calibration .............................................................................................................................. 3-46
Pressure Transducer Technology....................................................................................................... 3-46
3.7.3.1
Strain Gauge Sensors......................................................................................................... 3-47
3.7.3.2
Capacitance Sensors.......................................................................................................... 3-48
3.7.3.3
Quartz Crystal Sensors...................................................................................................... 3-49
Surface Data Acquisition ......................................................................................................................3-50
Downhole Data Acquisition.................................................................................................................3-50
3.7.5.1
Downhole Recording.......................................................................................................... 3-50
3.7.5.2
Surface Readout...................................................................................................................3-50
New Technology........................................................................................................................................ 3-52
3.7.6.1
Datalatch System................................................................................................................3-52
3.7.6.2
Wireless Telemetry ............................................................................................................ 3-53
3.7.6.3
Data Acquisition In Permanent Completions......................................................... 3-53
Formation Interval Testing ...................................................................................................................3-53
Preliminary Conditions On Oil Reservoirs.......................................................................................4-7
Sampling Gas Reservoirs..........................................................................................4-8
4.3.1
4.3.2
Preliminary Considerations On Gas Reservoirs.............................................................................4-8
Gas Reservoir Sampling Procedures...................................................................................................4-9
4.3.2.1
New Reservoirs Or Wells In Undepleted Zones ......................................................4-9
4.4
Sampling Of Volatile Oil Reservoirs..........................................................................4-9
4.5
Bottom Hole Sampling............................................................................................ 4-11
4.5.1
4.5.2
4.5.3
Well Conditioning For Bottom Hole Sampling.......................................................................... 4-11
Checking Bottom Hole Sample Validity....................................................................................... 4-13
Hydrogen Sulphide ................................................................................................................................... 4-15
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4.6
Bottom Hole Sampling Equipment ..........................................................................4-16
4.6.1
4.6.2
4.6.3
4.6.4
4.7
Field Estimation of Reservoir Properties .................................................................4-21
4.7.1
4.8
Section 5.0
Basic Assumptions ................................................................................................... 5-3
..................................................................................................... 5-8
Wellbore Storage.........................................................................................................................................5-9
Skin
......................................................................................................................................................5-10
Semi-Log Approach................................................................................................................................. 5-12
Log-Log Approach .................................................................................................................................... 5-13
Pressure Derivative .................................................................................................................................. 5-16
Superposition Theorem..........................................................................................5-17
5.3.1
5.3.2
5.3.3
5.4
Darcys Law....................................................................................................................................................5-3
The Diffusivity Equation...........................................................................................................................5-4
Infinite-Acting Radial Flow ....................................................................................................................5-5
IARF Solution: Log Approximation ....................................................................................................5-5
WTI Essentials
5.2.1
5.2.2
5.2.3
5.2.4
5.2.5
5.3
PVT Laboratory Measurement of Reservoir Properties .......................................................... 4-23
Basic Well Test Interpretation
5.1.1
5.1.2
5.1.3
5.1.4
5.2
Field Estimation of Reservoir Properties through Correlations...........................................4-21
4.7.1.2
Field Estimation of Reservoir Properties with
Fluid Properties Estimator............................................................................................... 4-21
Fluid Analysis and Uses of Data ...............................................................................4-23
4.8.1
5.1
Open Hole Sampling from Formation Interval Testing........................................................... 4-19
4.6.1.2
DST Sampling Tools.......................................................................................................... 4-16
4.6.1.3
Production Sampling Tools............................................................................................. 4-16
4.6.1.4
Transfer Benches.................................................................................................................4-17
Surface Sampling Equipment.............................................................................................................. 4-19
Sample Containers................................................................................................................................... 4-19
4.6.3.1
Gas Sample Bottles............................................................................................................ 4-20
4.6.3.2
Oil Sample Bottles ............................................................................................................. 4-20
New Developments .................................................................................................................................. 4-20
Principle ......................................................................................................................................................5-17
Mathematical Approach........................................................................................................................5-19
Superposition in Space: Boundaries................................................................................................ 5-22
Semi-Log Analysis ..................................................................................................5-23
5.4.1
5.4.2
5.4.3
MDH Plot (Dd #1).................................................................................................................................. 5-25
Horner Plot (Bu #2)................................................................................................................................ 5-26
Superposition Plot (all transients) .................................................................................................... 5-27
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Table of Contents
5.5
Well Models
5.5.1
5.5.2
5.5.3
5.5.4
5.5.5
5.5.6
5.5.7
5.6
5-44
Linear Boundaries..................................................................................................................................... 5-60
Circular Boundaries ................................................................................................................................. 5-62
Intersecting Faults.................................................................................................................................... 5-64
Parallel Faults (Channel) .....................................................................................................................5-65
Mixed Boundary Rectangle.................................................................................................................5-66
Gas Well Testing .................................................................................................... 5-67
5.8.1
5.8.2
5.8.3
5.9
Dual Porosity PSS (pseudo-steady state interporosity flow)................................................5-46
Dual Porosity (transient interporosity flow)................................................................................. 5-49
Double Permeability................................................................................................................................ 5-52
Radial Composite ..................................................................................................................................... 5-55
Linear Composite...................................................................................................................................... 5-57
Boundary Models................................................................................................... 5-59
5.7.1
5.7.2
5.7.3
5.7.4
5.7.5
5.8
Line Source Solution...............................................................................................................................5-29
Wellbore Storage and Skin..................................................................................................................5-31
Infinite-Conductivity or Uniform Flux Vertical Fracture....................................................... 5-33
Finite-Conductivity Fracture ............................................................................................................... 5-36
Limited-Entry Well.................................................................................................................................. 5-38
Horizontal Well......................................................................................................................................... 5-40
Changing Wellbore Storage.................................................................................................................5-43
Reservoir Models.........................................................................................................
5.6.1
5.6.2
5.6.3
5.6.4
5.6.5
5.7
.................................................................................................... 5-29
Pseudopressure and Pseudotime........................................................................................................ 5-67
Pseudo-Skin, S.......................................................................................................................................... 5-71
Absolute Open Flow ................................................................................................................................ 5-73
Curve Shapes
Section 6.0
.................................................................................................... 5-75
Nodal Systems - (Systems Analysis)
6.1
Introduction
6.2
Inflow Performance Curves......................................................................................6-4
6.2.1
6.2.2
6.2.3
6.3
Tubing Intake Curves .................................................................................................................................6-5
Horizontal Flow Curves ............................................................................................................................6-7
Other Considerations ..................................................................................................................................6-7
The Nodal Concept...................................................................................................6-8
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.4
......................................................................................................6-3
Example Problem 1.................................................................................................................................. 6-12
Example Problem 2.................................................................................................................................. 6-13
Example Problem 3.................................................................................................................................. 6-16
Example Problem 4.................................................................................................................................. 6-17
Discussion Of Example Problems 1 Through 4........................................................................... 6-19
Changes In Flow Conduit Size ................................................................................6-21
6.4.1
Example Problem 5.................................................................................................................................. 6-21
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6.5
Functional Nodes ...................................................................................................6-24
6.5.1
6.5.2
6.5.3
Surface Wellhead Choke......................................................................................................................6-24
Example Problem 6.................................................................................................................................. 6-25
Example Problem 7.................................................................................................................................. 6-30
6.5.3.1
Effects Of Separator Pressure........................................................................................ 6-31
6.5.3.2
Effects Of Flowline Size.................................................................................................. 6-32
6.5.3.3
Effects Of Tubing Size...................................................................................................... 6-32
6.6
General Discussion On The Effects Of The Variables ..............................................6-35
6.7
Graphical Representation Of The Total Producing System For One Well.................6-36
6.8
Summary
....................................................................................................6-37
Introduction to Well Testing (March 1998)
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