Production Packer
Types
There are several types of production packers. Several of the most common
types are identified below:
- Retrievable mechanical packers
- Hydraulic/hydrostatic set retrievable packers
- Permanent seal bore packers
- Retrievable seal bore packers
Mechanical Packers
Applications
Mechanical packers represent the most common packers used in the oil field.
Mechanical packers are set and released by manipulation of the tubing string.
Tubing string rotation and the application of weight or tension at the packer
are required to set or release. Mechanical packers can be set or unset without
being removed from the well for redress.They are suitable for application in the
following general conditions:
- Shallow to medium setting depths
- Low to moderately high pressures
- Straight hole or moderate deviation
Types
There are two basic types of Mechanical packers:
- Single grip retrievable packers (Fig 5-1) which are set and packed
the tension or compression force to be maintained in order for the
packer to remain set and packed off.
- Double grip retrievable packers (Fig 5-2) which contain some
is set. This type of packer may be further divided into two types:
- Those utilizing hydraulic accuated slips (holddown buttons), to prevent upward movement of the packer once it is set.
Tension Set Retrievable
Mechanical Packers
Mechanical Packers
Description
Single grip tension set mechanical packers (Fig 5-3) are not commonly used
nowadays except for shallow low pressure applications. Most models of tension
set packers utilize a secondary shear release system, which allows the packer
to be released by pulling a predetermined amount of tension on the tubing in
case the packer cannot be released using normal procedures.
Generally, tension set mechanical packers are best suited for applications in
which the expected pressure differential is from below, such as shallow injection
or disposal wells.
The model SA-3 (Fig 5-3) and the model ‘T’ retrievable packers (Fig 5-4) are
examples of mechanical tension set packers. The SA-3 is a single grip type in
which the slips hold in one direction only and so the packer will only remain set
so long as a tubing tension is maintained on the packer. The model ‘T’ is an
example of a double grip type tension packer, in that once it is set with the
proper amount of tension, it locks in that position and will remain set and
packed off independent of tubing forces, so long as the shear valve of the
secondary release is not exceeded.
Benefits of
Mechanical Packers
To prevent accidental release or failure, it is essential that an appropriate packer
design be used with the correct compression or tension applied. The benefits
of a retrievable mechanical packers include the following:
- Cost - Generally these packers require less initial investment
- Repeated use - The setting mechanism enables the packer to be
procedures.
- Versatile - Packer may be used for a variety of applications including
Compression Set
Single Grip Retrievable
Mechanical Packers
Single Grip Retrievable
Mechanical Packers
Description
Single grip compression set mechanical packers (Fig 5-5) generally utilize one
set of slips, that when activated, prevent the packer from moving down hole.
The continued application of tubing compression packs off the element system
which will remain packed off so long as sufficient compression force is
maintained.
Compression set packers are most suitable for applications in which the expected
pressure differential will be in favor of the annulus.
The model CA is an example of a very simple and basic compression set packer
suitable for shallow low pressure applications. The SR-2 (Fig 5-6) is an example
of a single grip compression set packer with a better element system plus an
equalizing system which makes it more suitable for higher pressure medium
depth applications. Compression set packers were once the most common
type of mechanical packer used, this type has been replaced in most completion
applications by the double grip type packers
Double Grip
Mechanical Packers
Mechanical Packers
Description
This type of retrievable packer has become the most common type of mechanical
set packers. Double grip mechanical packers are reliable and versatile packers
suitable for shallow to medium depth wells and applications where moderately
high pressures are expected.
Double grip packers are generally packed off with compression force. The
packer is unset with tubing manipulation. Most types of bi-directional packers
utilize a pressure equalizing system to prevent hydraulic problems when
releasing.
The SR-1 (Fig5-7) is an example of a mechanical double grip packer which
utilizes hydraulic upper slips. This type of packer must be set in compression
and tubing compression must be maintained. The hydraulic slips prevent the
packer from being forced up the well due to high pressures on the tubing side.
The SOT-1 (Fig5-8) is an example of a premium bi-directional retrievable packer.
The SOT-1 utilizes two sets of slips placed on either side of the elements. This
allows pressure differential forces across the elements to be taken directly by
the slips. This feature allows the packer to safely handle higher pressures than
other types of double grip packers which have both sets of slips below the
elements. The SOT-1 packer locks into the set position and once set, remains
locked independent of pressure and tubing forces.
Hydraulic Set
Retrievable Packers
Retrievable Packers
Hydraulic and/or hydrostatic-set retrievable packers are set without mechanical
manipulation of the tubing. After the packer is run to depth, hydraulic pressure
is applied to the fluid in the tubing string to set the packer. Once set, the packer
is mechanically locked in the set position. Release mechanisms vary and are
generally right-hand rotation or straight-pull release.
Types of Hydraulic Set Retrievable Packers:
- Single string differential set retrievable packer
- Single string hydrostatic set retrievable packer
- Selective set single string hydrostatic set retrievable packer
- Dual string hydrostatic set retrievable packer
- Multiple conduit hydraulic set retrievable packer
Operation
During the setting operation, the string is temporarily plugged below the packer
to allow pressure to be applied to the setting mechanism. At a preset value,
shear pins are broken allowing the packer slips to be forced out to engage the
casing wall and the sealing elements are compressed. A ratchet mechanism
locks the slips and packing in the set position. The packer can be mechanically
released using either rotation or a straight pull. Most models cannot be reset
once released.
The tubing is plugged during the setting process by one of the following
methods:
- Positive plug
- Pump open plug
- Pump out plug/ball
- Standing valve
Applications
Hydraulic set retrievable packers are suitable for application in the following
general conditions:
- Shallow to medium depths
- Low to medium pressure applications
- Multiple packer single string completions
- Dual string completions
- Selective set multiple packer completions
Advantages
- After the packer is set, energy is stored in the ratchet mechanism
securing the packer. Therefore, packer setting is not dependent
upon applied tubing force.
- Since the setting force is mechanically locked into the packer it is
above or below the packer.
- This type of packer may be set after the wellhead has been installed.
- Dual tubing string completions and multiple packer applications
movement in the setting process.
Hydro Packers
Differential Set
Hydraulic Packers
This type of packer is set by using the force generated by tubing pressure
acting on a piston against annulus pressure. A specific amount of differential
pressure (in favor of the tubing) has to be applied to complete the setting. The
Hydro-6 packer (Fig 5-9) is an example of this type of hydraulic packer.
With the increased demand for subsurface instrumentation and electric or
hydraulic operated devices, a new type of hydraulic set packer has been
developed to fulfill the requirement for multiple conductors to pass through
the packer without compromising the packers integrity. The model ‘MPP’
hydraulic set packer is an example of this type of packer.
Hydrostatic Set
Hydraulic Packers
These packers utilizing a setting piston similar to differential set packers, but
all or part of the piston area is acting against a chamber containing atmospheric
pressure rather than annulus pressure. This allows the hydrostatic tubing
pressure to assist the setting of the packer. Less pressure is required to generate
a required force than with a hydraulic set Packer. This allows hydrostatic set
packers to have a larger mandrel size than hydraulic set packers
Hydrostatic set packers are more expensive to manufacture than the differential
set and are normally used when larger tubing sizes are required. For example, in
7" casing with 2 7/8 tubing, a differential set packer will work fine but if 3 ½”
tubing is required a hydrostatic packer would be used due to the reduced
piston area resulting from the larger packer mandrel.
The Hydro-8 single string (Fig 5-11) and the Hydro-10 dual string packers are
examples of hydrostatic set packers. The Hydro-8 is also available in a selective
set version as well. Selective setting allows several packers to be run in a
tubing string and each packer to be set independently of the others. The
setting mechanism in each packer is activated by wireline intervention.
Permanent Seal
Bore Packers
Bore Packers
Description
As the name implies, permanent seal bore packers are just that: permanent.
Once set they cannot be unset and if their removal is necessary it must be done
using milling equipment to cut the packer out. This is the main disadvantage of
this type of tool. However, this also allows for several features which are
advantages over retrievable packers.
- incorporation of full 360º back-up on the packing element
- elimination of complicated pressure equalizing systems and their
- much greater slip coverage in the casing I.D.
- easier and more economical to manufacture in high alloy materials
- most models are suitable for high pressure application in wells of
- allow use of larger tubing sizes
packers are, but instead utilize a polished inside seal area into which a seal unit,
that is run as a part of the tubing string, seals into. This polished seal bore can
either be incorporated as a through bore in the packer or it can be incorporated
above the packer to accommodate larger inside seal diameters. Permanent seal
bore packers are run and set by one of the following three methods:
- Application of hydraulic pressure to an integral setting mechanism
- Application of hydraulic pressure to a separate recoverable and
- Reusable wireline setting tool utilizing an explosive charge to
Design
Figure 5-14 illustrates a basic wireline set permanent seal bore packer showing
the main components of the packer in both the running and set positions.
Options
Tubing-to-packer attachment and sealing in a seal bore packer is accomplished
using one of three basic seal assembly options.
- Latched or No-Motion (Also known as an Anchor Seal)-
assembly. The tubing is not free to move internally in the packer.
Forces on the tubing will be transmitted directly to the packer.
Such forces can result in failure of the top tubing joint (Fig 5-15).
- Limited-motion (Landed)- The stinger is fitted with dynamic
seal assembly allows limited movement downward, and uses a nogo
diameter to prevent the seals from moving completely through
the packer bore. This is useful for situations where cooling of the
tubing string (injection of cold fluid) and allows contraction of the
string without placing excessive tension of the top joint (Fig 5-16).
- Stung-through or Free-motion - This is useful in preventing
to an expansion joint and provides some freedom of tubing
movement (Fig 5-17).
Applications
Permanent seal bore packers are used in the following situations:
- Medium or deep set applications
- Deviated and extended reach wells
- Multiple packer completions
- Dual string completions with parallel flow tubes
- Sump packer for gravel packer operations
- Medium to high pressure application
Retrievable Seal
Bore Packers
Description
Retrievable seal bore packers utilize a seal bore similar to the permanent seal
bore packers. Because they are designed to be retrievable most retrievable seal
bore packers have a lower pressure rating than permanent seal bore packers
and are generally more expensive. Retrievable seal bore packers are commonly
used in gravel pack operations as well as completions.
The retrievable seal bore packers utilize many of the same accessories such as
setting adapters, seal assemblies, etc. as the permanent packers. They also are
available in both wireline set versions and self contained hydraulic set versions.
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