Well Completions

Maria Cepeda, Jordan Arvie, Abdulmajeed Aldughaither,

Christian Brown, Da’Juan Chaney & Delvin Nguyen-Ho
Overview

■ What is well completions?

■ Completion types
■ Tubing Selection
■ Packer Selection
■ Sub-Surface Safety Valves
■ Control/ Injection Line Selection
■ Perforation
■ Sand Control Methods
■ Artificial Lift
■ Wellhead Selection
■ Stimulation
 What do we mean by completing a well?

■ Transforming the drilled well into a producing one.

■ Installing equipment to recover safely and efficiently a large % of the OIIP.
■ Goal is to establish a mechanical connection between reservoir and well.
– Keep water and sand out
– Keep formation from collapsing into the well.
– Let oil into the well
■ Decision to be made: P&A the well if not enough hydrocarbons or begin to complete
the well.
To Begin the Well Completion Process:
■ After casing is ran and cemented:
– Completion fluid is pumped to remove the drilling mud from the
hole and prepare the well for the flow of hydrocarbons.
– A string of tubing is put into the well to recover formation fluids.
– Formation is then perforated
■ Cement Bond Log can be ran to make sure cement sheath between
casing and borehole wall is without flaws.
– The wellhead is installed afterwards
■ How do we select our completion type?
– Depends on well location, environment, artificial lift method (if
applicable), cost.
– Completions should be simple & cost-effective.
■ At the end of the process, riser is removed, BOPs are removed &
production wellhead is installed on the surface.
Completion Types- Reservoir & Wellbore Interface
OPEN HOLE COMPLETIONS

■ Open hole Completions

– Involves setting production casing above pay
zone
– Predominantly in thick carbonate or hard
sandstone reservoirs
– Key issues:
■ Risk of causing damage to well productivity
w/ cased and perforated completion?
■ Zonal sensitivity required?
■ Fracture Stimulation Required?
■ Any potential sand production?
■ Open hole gravel packs
■ Used for too fine or abrasive sands
■ The most effective sand control measure
Completion Types- Reservoir & Wellbore Interface
OPEN HOLE COMPLETIONS

■ Extra key issues for open hole gravel pack:

– Loss circulation control during under-reaming and tripping, and how the
LCM can be removed before gravel packing
– The stability of hole
– Gravel pack design (grain size, length of blank pipe, volumes,reserve
volume, etc.
– Type of gravel pack and will it double as the production packer
Completion Types- Reservoir & Wellbore Interface
UNCEMENTED LINER COMPLETION

■ Uncemented Liner Completion

– Used to overcome production problems associated
with open hole completions and to extend their
application to other formations
– Key Issues: Same as open hole completions
■ Slotted liner
– Used when there is wellbore stability issues.
■ Wire wrapped screens
– Plain wire screen used to filter out sand, and helps in
liquid lift due to the smaller flow area.
Completion Types- Reservoir & Wellbore Interface
UNCEMENTED LINER COMPLETION

■ Key issues: Same as open hole completions

– Extra Key issues for slow liner:
■ Whether or not to use more expensive wire wrapped screen
■ Slot width requirement
■ Clearance required for washover, and whether centralisers should be
expandable, or millable, solid type
■ Gravel Pack may be a better option
Open Hole and Uncemented Liner Interface Options

Figure 5.C - Open Hole and Uncemented Liner Interface Options (ENI Drilling
Design Manual)
Completion Types- Reservoir & Wellbore Interface
PERFORATED COMPLETIONS
■ Perforated Completions: the most common world-wide.
– Lower cost, safety, fluid selectivity
■ Types:
– Standard perforated
■ When rock is stable and permeable.
■ Uses explosive charges
■ Cased hole gravel packs
– Used to control sand production
– Place between cased hole and sand screen
– Fractured Stimulation
■ Used to improve permeability by increasing IPR of <25 md rocks.
■ Equipment need to be designed for additional loading of stimulation
operation
Completion Types- Reservoir & Wellbore Interface
PERFORATED COMPLETIONS
■ Key issues:
– Perforate interval selection, gun type, show density, etc.
– Completion fluids programme selection with regard to fluid quality and formation
damage
– Type of formation, and if special perforation technique needed
– Effective zonal isolation due to cement quality and distance between zones
Perforated Completions

Figure 5.D - Perforated Casing Interface Options (ENI Drilling Design Manual)
Completion Types- Reservoir & Wellbore Interface
Multi-Zone Completions

■ 4 main methods to complete multi-zone wells:

■ Commingled production
– Allowing all zones to produce together
■ Sequential zonal production - This preference is subject to economics,
reservoir management and regulatory requirements
– Through live well intervention methods
– By re-completion
■ Single string multi-zone segregated production
– By initial (or eventual) commingling
– By sequential (or alternating) production
■ Multi-string (dual) multi-zone segregated production
– Using parallel strings
– Using concentric strings
Tubing Selection- Terminology

■ Sour service:Well environment containing H₂S

■ Sulfide Stress Cracking (SSC): Brittle failure in steels when in contact with H₂S or
other environments containing sulfur.
■ Corrosion: loss of metal due to chemical or electrochemical reactions. It can
occur either at the bottomhole or at the surface.
■ Hydrogen Embrittlement: Hydrogen causing steel components to be much
weaker in tensile strength when exposed to gaseous or liquified H₂S
Tubing Selection
■ Must be carefully selected to produce efficiently, for artificial lift installation.
■ Must be able to withstand stresses.
■ Tubing is exposed to corrosive fluids, HPHT environments.
■ The liner or production casing may come in contact with produced fluid
– Recommended to choose same material as that for the tubing.
■ Parameters to consider:
– Min & max temperature and pressure.
– Hydrogen Sulfide H₂S (liquid & gas) , CO₂, chloride concentrations.
■ Material
– API standard Steels → standardized chemical content & mechanical properties
■ J-55, N-80, C-75, L-80, C-90 and P-105 → Letter points to the chemical
composition, # is the min yield strength in 1000 psi.
– CRAs (Corrosion Resistant Alloys)
■ Stainless Steel: 9 Cr (Sour Service ), 13 Cr (for CO₂ without H₂S present)
Tubing Selection-API Standard Steel Grade
Selection
Tubing Grade Applications/Characteristics
• Relatively low yield strength
H-40 • Used for non-critical, shallow wells
• Not for sour service applications.
J-55 • Used for shallow tubing set <9,000 ft and low pressures <4,000 psi wells on land.
• Sweet oil and gas wells
N-80 • Fit for H₂S service
• Susceptible to SSC (Sulfide Stress Cracking)
• Fit for sour service
L-80 • 3 Chemical requirements (Type 1, 2 & 3)
• Maximum hardness requirement
• Maximum hardness requirement
C-90 • Type 1: recommended for sour service

• Only Type 1 is recommended for sour service

T-95
• SSC resistant
• High strength tubing used in deep sweet oil and gas wells with high pressures.
P-110
• Sensitive to SSC unless temps are >175 F
 Tubing Selection -CRAs

● For Sour Service , more $$$ than CS

● CRAs classified in ascending cost and corrosion
resistance
○ CRA chosen on presence of sulfur, CO2, H2S,
chloride conc & Temp.
○ Martensitic Stainless Steel (MSS), Duplex and
Super Duplex Stainless Steel (DSS & SDSS),
Super Austenitic Stainless Steel, and High
Nickel Alloys.
Tubing Selection- Cost-Effective Alternatives

● Coatings are the alternative (p 183) Ex: Three-Layer Polyproylene (3LPP) as an external
coating on the steel to prevent corrosion.
● Clad Pipe: getting advantage of 2 materials at low cost
○ High strength carbon steel on the outside and high corrosion resistant alloy on the
inside. Used in HPHT environments. Done by welding or explosive bonding.

Clad pipe 3LPP corrosion prevention coating

Tubing Connectors
■ Tubing screwed together through connections
■ API developed specifications for 3 different tubing connectors:
– 1. External-upset-end (EUE)
■ Outside thickening at end of joint so that the ID of it
remains the same.
■ widely used. 100% joint efficient connection (high
joint strength & pressure)
■ come in OD sizes of 1.050 to 4.500 in.
– 2. Internal-upset tubing
■ Inside thickening at end of the joint so that OD
remains the same
■ Used less than the EUE, joint strength < EUE’s
■ OD sizes of 1.050 to 4.500 in.

Refer to: API Spec 5CT

Tubing Connectors
3. Integral joint tubing
- Pipe with built-in threads, female/Box end and
male thread/ pin end welded.
- Ex: bottle (male) & cap (female/box)

Female/Box end Male/Pin end

Tubing Connectors

■ Premium connections
– Proprietary
– Offer features not available on API connections
– Preferred for wells in corrosive settings, high P.

■ Importance of connections
– Properties are enhanced. For ex: X-80 pipe with an
H-90 welded box. Higher yield with connection.
 Packer Selection
Casing & Tubing Interface
■ Packer- device that seals the wellbore to redirect
fluid flow into the tubing and not the annulus.

Type of Packer Description Setting Method

Set in the production casing or

Wireline/ Tubing tension/
liner before the tubing is run.
Permanent hydraulic pressure/ tubing
Retrieved from the well by
rotation
milling.

Installed & retrieved on the Hydraulic pressure/ tubing

Retrievable production tubing. Ex: rotation
single-grip, double-grip.

Packers than can be installed as

Permanent/Retrievable permanent or retrievable Mechanical
packers.
 Procedure to Select Packers

1. General well data

a. Location(on/offshore?), well type(P or I),
type of fluid produced.
2. Completion Data
a. Type and density of the completion fluid
b. Perforation technique
c. Production liner?
3. Well classification (see figure on the right)
a. If Highly Corrosive→ permanent/retrievable
or permanent packer.
b. If Highly Critical well→ permanent packer
c. If critical or non-critical (refer to flowchart on
Source: ENI Completion Design Manual (Pg.209)
the next slide)
Type of Packer for Critical & Non-Critical Wells
Source: ENI Completion Design Manual (Pg. 210)
Packer Setting Method for Critical & Non-Critical Wells
Source: ENI Completion Design Manual (Pg. 211)
Packer Setting Method for Retrievable Packer
Source: ENI Completion Design Manual (Pg. 211)
Sub-Surface Safety Valves

The choice of SSSV for a particular development will depend on:

• Well location
• Fluid properties
• Required flow area
• Well intervention capabilities
Surface Controlled Sub-Surface Safety Valves
SCSSSV
Sub-Surface Safety Valves
Control/Injection Line Selection

Control Lines
Tube used as ‘control line’ to operate downhole safety valves are installed along with
the production string. In this case, SCSSV’s are usually set at shallow depths and,
therefore, the length of line required is generally relatively short.
Injection Lines
Tube used as ‘injection lines’ to inject chemical products such as corrosion or scale
inhibitors down hole or as deep as possible in the well, are also installed with the
tubing string. The line length required in this case, will be considerably longer
Control/Injection Line Selection

Control Line Working Pressures

WP = Safety Valve WP + Valve Opening Pressure

Safety Valve WP is as specified by the manufacturer.
Valve Opening Pressure, provided by the manufacturer, is the pressure required to
overcome the closing force of the spring plus resistance due to friction effects. Usually
it ranges between 1,500 to 2,000 psi depending on the manufacturer.
Control/Injection Line Selection

Injection Line Working Pressures

Control/Injection Line Selection
Control/Injection Line Selection
Control/Injection Line Selection
Control/Injection Line Selection
Control/Injection Line Selection
Perforation

■ The Purpose of Perforations:

- Perforations are used once tubing selection has been completed, and the hole
has been cased
- Used to establish a flow path between the zone of interest, and the well bore
- Serves as the first indication of a productive field.
Perforation Design

■ Bullet guns were the first perforating device commercially available in the early
1930’s: Using the ignition of gunpowder to create a controlled explosion allowing
perforations to be made
■ The bazooka gun became popular in the late 1940’s and became the most
practical device that became used throughout the industry.
■ Modern day perforation guns have been designed to improve the quality of
perforations, and optimizing the flow path of oil.
Types of Perforations

■ There are three types of perforation designs used within the industry
- Through Casing Perforation
- Through Tubing Perforation
- Tubing Conveyed Perforation
Types of Perforating Guns

■ Exposed Guns (Capsule Gun)

■ Hollow Carrier Guns
Exposed/Capsule Gun

■ Two types
- Expendable
- Semi-expendable
■ Individually shaped charges that are sealed
■ Sent downhole by a wireline
■ Detonation cord is exposed, therefore comes into contact with borehole fluids
■ May leave hole debris once it is fired
■ Approximately 2’ ½’’ inches in diamter.
Hollow Carrier Gun

■ Widely used throughout the industry due to the versatility of its design
■ Four Types
- Scallop Gun
- Port Plug Gun
- High Shot Density Gun
- High Efficiency Gun
■ Each gun provides different features that allow adjustments to changing
conditions
Specialty Perforation Guns

■ Specialty Perforations guns are used in unique well bore cases, such as
underbalanced perforations, or Tubing Conveyed Perforations
■ They include:
- Laser
- Hydraulic Punches
- Mechanical Punches
- Water Jet
- Combination Bullet/Jet Guns
- Electric Arc
Choosing the Correct Gun

■ Perforating guns depend on the characteristics of each well

■ Lithology, depth, and the type of completion chosen are all factors when
selecting the correct perf gun.
■ The following questions help distinguish what type of design needed for several
completion decisions.
 Gravel Packing & Solids Control
■ A gravel pack is simply a downhole filter designed to prevent the production of
unwanted formation sand.
■ In gravel pack operations, a steel screen is placed in the wellbore and the
surrounding annulus is packed with prepared gravel of a specific size designed to
prevent the passage of formation sand.
■ The formation sand is held in place by properly sized gravel pack sand that, in
turn, is held in place with a properly-sized screen.
■ To determine what size gravel-pack sand is required, samples of the formation
sand must be evaluated to determine the median grain size diameter and grain
size distribution.
■ The primary objective is to stabilize the formation while causing minimal
impairment to well productivity.
■ Depending on the well, production rate, and size of tubing a gravel pack may or
may not be necessary.
– Always do a cost analysis when making these decisions.
Gravel Packing & Solids Control
Gravel Packing & Solids Control

■ The first step in gravel-pack design is to obtain a representative sample of the

formation.
– Failure to analyze a representative sample can lead to gravel packs that fail
because of plugging or the production of sand.
■ These are a few different techniques in order to obtain a formation sample:
– Produced Samples
– Bailed Samples
– Sidewall Core Samples
– Conventional Core Samples
– Other Samples from Offset Wells
Sand Sieve Analysis
■ A sieve analysis is a laboratory routine
performed on a formation sand sample for the
selection of the proper-sized gravel-pack sand.
– Sample every 2-3 ft or lithology change.
■ A sieve analysis consists of placing a formation
sample at the top of a series of screens that
have progressively smaller mesh sizes
downwards in the sieve stack.
■ Once this is done place in a vibrating machine
and the sand grains in the sample will fall
through the screens until encountering a screen
through which certain grain sizes cannot pass.
■ By weighing the screens before and after
sieving, the weight of formation sample,
retained by each size screen, can be
determined.
Gravel Pack Sand Selection

■ The most widely used sizing criterion provides sand control when the median
grain size of the gravel-pack sand, D50 , is no more than six times larger than the
median grain size of the formation sand, d50.
– The upper case D refers to the gravel, while the lower case d refers to the
formation sand.
■ In practice, the proper gravel-pack sand size is selected by multiplying the
median size of the formation sand by 4 to 8 to achieve a gravel-pack sand size
range, in which the average is six times larger than the median grain size of the
formation sand.
– The gravel pack is designed to control the load-bearing material and not the
formation fines that make up less 2-3% of the formation.
■ To ensure maximum well productivity, one should use high quality gravel-pack
sand.
Artificial Lift

■ Artificial lift is a method used to lower the producing bottomhole pressure (BHP)
on the formation to obtain a higher production rate from the well.
– Since we are looking to produce at a high flow rate, we will need to
incorporate an artificial method.
■ There are three types of artificial lift methods we will focus on:
– Electrical Submersible Pumping
– Gas Lift
– Hydraulic Jet Pumping
 Electrical Submersible Pumping

■ The electrical submersible pump, typically

called an ESP, is an efficient and reliable
artificial-lift method for lifting moderate to
high volumes of fluids from wellbores.
■ These volumes range from a low of 150 B/D to
as much as 150,000 B/D.
■ These will only tolerate minimal percentages
of solids (sand) production.
■ Costly pulling operations and lost production
occurs when correcting downhole failures,
especially offshore.
■ Also have to select the correct number of
stages based on the efficiency of the pump and
the amount of pressure the well needs to reach
the desired flow rate.
Gas Lift

■ Gas lift uses an external source of high-pressure gas for supplementing formation
gas to lift the well fluids.
■ The injection gas mixes with the produced well fluid and decreases the density.
The decreased flowing pressure gradient reduces the flowing bottomhole
pressure below the static bottomhole pressure thereby creating a pressure
differential that allows the fluid to flow into the wellbore.
■ Good for offshore operations, but we would need an outside source of gas.
■ Gas lift is the best artificial lift method for handling sand or solid materials.
■ Most commonly used in the GOM.
Hydraulic Jet Pump
■ High-pressure power fluid is directed
down the tubing to the nozzle where
the pressure energy is converted to
velocity head.
■ Can also reverse this directing the
power fluid down the annulus.
■ The high-velocity, low-pressure
power fluid entrains the production
fluid in the throat of the pump.
■ A diffuser then reduces the velocity
and increases the pressure to allow
the commingled fluids to flow to the
surface.
Hydraulic Jet Pump

■ The most significant feature of this device is that it has no moving parts; the
pumping action is achieved through energy transfer between two moving streams
of fluid.
■ With no moving parts, jet pumps are rugged and tolerant of corrosive and abrasive
well fluids.
■ Their reliability, low maintenance costs, and volume capability make them
attractive in many wells.
■ Jet pumps typically have low pump-repair costs but have high
energy-consumption expenses because of low pump efficiencies.
■ A higher pump-failure rate can be acceptable if a free system is present and the
pumps can be retrieved quickly without pulling the tubing.
■ Be sure to select a tubing grade that will be able to handle the additional pressure
(burst & collapse).
Hydraulic Jet Pump
Wellhead
■ A type of equipment used to carry casing and completion load to be transferred
into the ground
■ Isolates the top of the tubing-casing annulus
■ Mates and seals with the xmas tree.
■ The wellhead assembly consists of:
– Casing head Spools
– Tubing hanger
– Xmas tree
Wellhead - Components
■ Casing Head Spools - A wellhead component use to secure the upper end of a
casing string.
– Available in various range of sizes and pressure ratings.
■ Tubing Hanger Systems - A device attached to the topmost tubing joint in the
wellhead to support the tubing string. It also incorporate a sealing system to
ensure that the tubing conduit and annulus are hydraulically isolated
– 5 common types
■ Slip and seal assemblies
■ Mandrel compression hangers
■ Ram type tension hangers
■ Downhole tubing hangers (e.g. annular safety system)
■ Direct attachment to the Xmas tree (threaded)
■ Xmas ( Christmas) Tree - An assembly of valves, spools, pressure gauges, and
chokes fitted to the wellhead to control production.
– Available in wide range of sizes and configuration such as low- or high-
pressure capacity and single- or multiple-completion capacity
Wellhead Selection

■ The team must determine whether the formation is on land or offshore

■ Here are various selections for on land or offshore wellhead equipment:
– MSCL - Modular Single Completion Land
– DCSFSL - Dual Completion Seal Flange solid-Block Land
– SCSO - Single Completion Seal Flange Offshore
– DCSO - Dual Completion Solid-Block Offshore
■ The team must also determine whether they need:
– Class A - Equipment designed to operate up to 5000 psi WP
– Class B - Equipment designed to operate up to 10000 psi WP
■ When deciding which wellhead the team should look at the API specifications of
the material as to make sure the material can withstand formation condition.
Wellhead Selection - Specifications
■ Wellhead Specifications are rated by:
– Maximum work pressure according to the maximum anticipated surface
pressure
– Temperature operating range
■ Above 250 F the working pressure is de-rated against temperature (down
to 72% of rating at 650 F)
– Retained fluid rating
– Product Specification level, PSL

Table 5.A - API Temperature Classifications ( ENI Completion Design Manual)

Wellhead Selection - Specification

Table 8.A - Eni-Agip Standard Wellhead Equipment Chart (ENI Drilling Manual)
Stimulation - 2 types

1. Hydraulic fracturing

2. Acidization
Hydraulic Fracturing

■ Injecting fluid into the formation at a high rate.

■ Leads to formation fracture.
■ Proppant is used to keep the fracture open ( e.g sand)
■ Criteria:
- Medium- High pressure
- High Skin Factor
 Fracturing Fluid

■ Compatible with the

formation
■ Creates enough pressure to
fracture
■ Low Viscosity ( transport
proppant back to surface)
Proppant
Acidization

■ Injecting Acid into the hole/formation

■ 3 types:

1) Acid cleaning: Commonly used with HCL. Cleans out the hole (scale, rust, and
other debris restricting flow).
 2) Matrix Acidization

■ Acid is injected under the fracturing

pressure into the formation.
■ Makes the flow of hydrocarbon easier
by breaking down the formation
■ Effective in sandstone formation and
permeability greater than 10 mD
3) Fracture Acidization

■ Acid enters the formation at a pressure greater than its fracturing pressure
■ No need for proppants.
■ Criteria:
■ Low Temperature (less than 200 F)
■ Carbonate formation
■ Shallow Zones
Sources

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