Sample Completion Configurations lec ( 12 )





Single Zone
Completion #1

A single zone completion using a hydraulic set retrievable packer is a simple,
very commonly used design.
Design Advantages ❑ Retrievable
  • ❑ Allows circulation above the packer
  • ❑ Packer may be set after well head installation
  • ❑ Flow may be controlled or shut off using the profile nipples and/or
sliding sleeve
  • ❑ Design allows for the installation & retrieval of recording devices
and flowing pressure / build up data acquisition.
Design Disadvantages
  •  ❑ Suitable for low to medium pressure differentials only
  • ❑ Limited ability to handle tubing forces
  • ❑ Limited material selection
Additional Equipment
That Could Be Added
  • ❑ Flow couplings if required
  • ❑ Artificial lift equipment
  • ❑ Safety valve



Single Zone
Completion #2

A single zone completion using a high performance retrievable mechanical
double grip packer is a common completion design primarily used in single
zone gas well completions
Design Advantages 

  • ❑ Retrievable
  • ❑ Allows circulation above the packer
  • ❑ Packer may be utilized as a bridge plug
  • ❑ Flow may be controlled or shut off using the profile nipples and/or
sliding sleeve
  • ❑ Design allows for the installation & retrieval of recording devices
  • ❑ Design is capable of handling medium high differential pressures
and high tubing forces
Design Disadvantages 
  • ❑ limited material selection
  • ❑ Pressure handling capability of some sizes may be limited
Additional Equipment
That Could Be Added
  • ❑ Flow couplings if required
  • ❑ Artificial lift equipment
  • ❑ Safety valve
  • ❑ TCP assembly



Single Zone
Completion #3

This is a common completion used in underbalanced perforating of single zone
wells.
Design Advantages 
  • ❑ Retrievable
  • ❑ W/L setting allows exact depth control
  • ❑ Packer may be utilized as a bridge plug
  • ❑ Allows flow control using profile nipples
  • ❑ Design is capable of handling medium high differential pressures
and high tubing forces.
Design Disadvantages 
  • ❑ Limited material selection
  • ❑ Pressure handling capabilities of some sizes may be limited
Additional Equipment
That Can Be Added
  • ❑ Flow couplings if required
  • ❑ Artificial lift equipment
  • ❑ Safety valve
  • ❑ Sliding sleeve



Single Zone
Completion #4

This is a typical shallow to medium depth permanent seal bore packer completion
primarily used on natural gas wells.
Design Advantages 
  • ❑ Good pressure handling capability
  • ❑ Suitable for sour completions
  • ❑ Good flow control with profile nipples and the sliding sleeve
  • ❑ Design allows for use of recording devices in the tail pipe
  • ❑ Good material selection
Design Disadvantages 
  • ❑ Packer is not retrievable
  • ❑ Plugs used in the nipples below the packer are susceptible to fill
Additional Equipment
That Can Be Added
  • ❑ Mill out sub
  • ❑ Flow couplings if required
  • ❑ Artificial lift equipment
  • ❑ Safety valve
  • ❑ TCP assembly
  • ❑ On/off tool




Single Zone
Completion #5

This is an example of a deeper single string gas well completion which allows
for tubing movement.
Design Advantages 
  • ❑ Suitable for high pressure sour applications
  • ❑ Locator seal assembly can be spaced out to allow for anticipated
tubing movement
  • ❑ Mill out sub allows for one-trip removal of the packer and tail pipe
  • ❑ Design allows for pressure recorder installation in the tail pipe
Additional Equipment
That Can Be Added
  • ❑ Safety valve
  • ❑ Sliding sleeve above the seal assembly to allow circulation above
the packer
  • ❑ Chemical insection nipple or mandrel above the seal assembly



Single Zone
Completion #6

This is a common permanent packer single string completion used in deeper
hostile environment gas wells.
Design Advantages 
  • ❑ Largest possible through bore
  • ❑ Primary seal bore is retrievable
  • ❑ Sliding sleeve allows circulation above the packer
  • ❑ Design incorporates provision for recorders in the tail pipe
Additional Equipment
That Can Be Added
  • ❑ Safety valve
  • ❑ Chemical infection valve
  • ❑ Gas lift equipment


Dual Zone Single String
Completion

This type of completion is commonly used in shallow low pressure sweet
natural gas wells in North America. Lower zone is produced up the tubing
string and upper zone up the annulus.
Design Advantages 
  • ❑ Economical
  • ❑ Retrievable
  • ❑ Packer may be utilized as a bridge plug
  • ❑ Good flow control with profile nipples and sliding sleeve
  • ❑ Allows for installation and retrieval of recorders
Design Disadvantages 
  • ❑ Suitable for shallow “sweet” completions only
  • ❑ Suspectable to fill problems from upper zone
Additional Equipment
That Can Be Used
  • ❑ Provision for rod pump, plunger lift or siphon tube



Dual Zone Dual String
Completion

This is a common completion type used in those wells where it is advantageous
to produce two zones simultaneously.
Design Advantages 
  • ❑ All equipment is retrievable
  • ❑ Both zones can be produced independently and simultaneously
  • ❑ Packers may be set after the well head is installed
  • ❑ Sliding sleeve may be used to open communication between the
tubing strings
Additional Equipment
That Can Be Used
  • ❑ Sliding sleeves above the dual string packer
  • ❑ Well configurations in both tail pipe assemblies for recorders
  • ❑ Selective set packers
  • ❑ Gas lift equipment
  • ❑ Safety valves




Multi Zone Single String
Completion

This completion design allows the selective production of multiple zones up
one string of tubing.
Design Advantages
  • ❑ Allows control of each zone individually
  • ❑ Retrievable
  • ❑ Hydraulic packers may be set after installation of the well head
Design Disadvantages 
  • ❑ Restricts production to one zone at a time
  • ❑ Limited material selection in packers
  • ❑ Limited ability to handle tubing forces
Additional Equipment
That Can Be Added
  • ❑ Sliding sleeve above top packer to allow circulation between the
annulus and tubing
  • ❑ Blast joints
  • ❑ Recorder provision below lower packer

Materials lec ( 11 )


Material Selection

 In general, oil and gas wells are hostile environments. Consequently, careful
consideration must be given to the materials from which completion components
are manufactur. A wide variety of materials, with a range of physical properties,
have been developed specifically for use in downhole completion components.
In severe cases, it may be necessary, or cost effective, to incorporate a system
which resists the harmful effects of agents present in the wellbore or reservoir
fluid.
Proper selection of completion materials is a key factor in ensuring completion
longevity. However, it is important that the design life of the completion is
compatible with the production profile of the well or field (Fig. 8-1).

Well Life Design

Material Selection Criteria

 Completion components must be chosen to resist the damaging effects of
pressure, temperature and corrosion. In addition, recent exploration and
completion operations have resulted in wells being drilled deeper with higher
pressures and temperatures being encountered.
Material selection criteria for oilfield equipment are typically determined by the
following categories:
  •  Mechanical properties (function)
  •  Operating environment
  •  Cost
  •  Availability
  •  Stock size and shape
These categories relate to the selection of metals, elastomers and plastics used
in construction of downhole tools and equipment. They are not listed in order
of priority since they may change for different applications.

Ferrous Alloy
Compositions
and Characteristics




Non-Ferrous Alloy
Compositions
and Characteristics




Packer Component
Materials

A sample material list for a standard service medium pressure hydraulic set
retrievable packer

Material Applications

 Weight or stress bearing components, such as the outer bodies of safety
valves, packers, etc., are know as stagnant flow components. They may be
made of a different material than the internal components (mandrels, flow tube,
flapper, etc.). Internal components that are exposed directly to corrosive well
fluids are known as flow wetted components.
Examples of material applications are shown in Fig 8-4.

Non-Metallic Components 

Elastomers and plastics are blended and synthesized organic polymers.
Polymers are repeating units of organic compounds. The flexibility of the
linking bonds between these units is what gives elastomers and plastics the
ability to stretch and then return to their original shape. The primary purpose
of elastomers and plastics in downhole tools is to provide seal materials to
isolate pressure, liquids, gases, or heat.
Many elastomers and plastics are available, each with different inherit qualities.
Elastomers function quite well in most wellbore environments but problems
can arise under the following conditions:
  •  Certain corrosive environments
  •  Wide temperature fluctuations
  •  Extreme pressures
The completion technologist should be aware of downhole conditions,
especially temperatures, to enable selection of the correct elastomers (seal
and o-ring) for a specific application.


General Seal
Materials Guide



Elastomers 

There are two major types of polymer materials, elastomers and plastics. They
are differentiated on the basis of their elastic properties although there is no
sharp distinction between them. Polymers may be blended with other materials
to create substances with specific properties. An elastomer is a material which
can be stretched at least twice its length and upon release of the stress will
quickly return to approximately its original length.
Materials are added to elastomers and plastics to increase the strength, stiffness,
oil resistance, low temperature resilience, high temperature resistance and to
lower the friction coefficient. Unfortunately, whenever materials are added to
enhance one quality, another quality often suffers.
Polymers are blended for construction of O-rings, seals and packing elements.
The most common type of elastomer is Nitrile. This substance is also know as
Buna-N or Hycar (brand name). Other common materials are Viton and Aflas
which are fairly strong and resistant to degradation from exposure to wellbore
fluids.
Polymer materials are used as high performance packing for moderate
temperatures, pressures and corrosion. When completion tools must be
installed in wells where the temperature is very high, or in an H2S environment,
elastomers of fluorocarbons are used. Fluorocarbon elastomers can be
compounded with many substances including glass and asbestos, thereby
improving resistance to extrusion.
Plastics are also used in the manufacture of completion tools and equipment.
There are two major types of plastics:
  •  Thermoplastic - Formed by melting a resin, pouring the resin into a
mold and letting it cool to harden.
  •  Thermosetting plastic. - Plastic in a liquid form is poured into a
mold and heat or hardening agents are applied to produce certain
chemical changes that cause the plastic to harden into the shape
of the mold. Once a thermosetting plastic has been formed it will
not melt, at least not at normal temperature. Examples of
thermosetting plastics are Teflon, Loctite and Eastman 910 (brand
names).
Teflon has probably the greatest oilfield application of the thermosetting
plastics. It has a high resistance to both high and low temperature, very low
friction and is inert to most fluids.
Teflon is used to form seal rings. However, to be efficient they must be
mechanically energized to make and maintain a seal. For this reason, Teflon
seals are usually used as back-up or secondary seals in high pressure
applications.
A number of new exotic plastics have been developed which show a high
degree of resistance to H2S, high pressure, and temperature conditions.
Fig 8-8 illustrates many of the common polymers used in oilfield tools.

Forces lec ( 10 )



Tubular Forces 

Determining the stress levels that the completion string and components will
be subjected to, under the best and worst conditions, is a critical step in
completion design. Properly assessing the length and force changes will avoid
premature failures and costly remedial operations.
  •  Temperature
  •  Pressure
  •  Weight
  •  Fluid gradients
  •  Friction
Tubing Forces



 Each completion will have a variety of downhole conditions which affect the
total design, choice of downhole tools and the operation of the completion
components once in place. Changes in temperature, pressure, applied weight,
fluid gradients and friction are a few of the variables that must be considered.
The choice of completion equipment not only must meet minimum stress
requirements, but they themselves contribute directly to these stress
calculations. The illustration in Fig 7-1 summarizes the principal variables that
need to be considered in a completion operation.For more detailed discussion
on basic forces refer to the “ Completions Hydraulics Handbook.”

Factors Influencing
Completion String Length
and Force Changes





Length and
Force Changes


The most important aspect when evaluating a packer installation is the
determination of the length and force changes due to varying pressures and
temperatures. When the magnitude and direction of these length and force
changes have been calculated, this information can then be used as shown
below.
  •  To aid in the packer selection process
  •  To determine if tubing damage will occur
  •  To determine the proper spacing-out procedure for the packer and completion components

There are four different effects which create length and force changes. Each of
these effects must be analyzed and combined to assess the total effect for any
packer installation.
  •  Piston effect
  •  Buckling effect
  •  Ballooning effect
  •  Temperature effect
This piston effect, bucking effect and ballooning effect result from pressure
changes in the system. The temperature effect is related only to temperature
change and is not affected by pressure changes. While some effects are
related to each other, each must be calculated individually. Each calculated
effect will be a magnitude and direction. Once each effect is known, they are
combined to obtain the total effect. The decision to add or subtract when
combining is based on the direction that each effect (resultant force) acts.
The approach used to evaluate packer installation problems will depend on the
type of tubing-to-packer hookup being considered. If the packer system will
not permit length change in the direction of the total effect, then the packer
installation is evaluated by calculating the force changes. If the packer system
permits length change in the direction of the total effect, then the calculation
would be as a length change.

Piston Effect 

See Completions Hydraulics Handbook