Production Packers

1.8.12 Production Packers

A production packer may be defined as a sub-surface component used to provide a seal between the casing and the tubing in a well to prevent the vertical movement of fluids past the sealing point, allowing fluids from a reservoir to be produced to surface facilities through the production tubing.

NOTE: By no means are all wells completed with production packers.

However, for the purposes of this course, only those packers used in well completions will be discussed.

The prime purpose of using a packer or packers in a well completion is as follows:

• To protect the casing from reservoir fluids

• To protect the casing from the effects of flowing pressures

• To isolate various producing zones

In general, packers are constructed of hardened slips which are forced to bite into the casing wall to prevent upward or downward movement while a system of rubberised elements contact the casing wall to effect a seal.

Production packers may be grouped according to their ability to be removed from a well, that is, retrievable or permanent.

Retrievable Production Packers

Are run on the tubing string and may be set mechanically or hydraulically. They are usually removed from the well by the application of mechanical forces. An example of a retrievable production packer is shown in Figure 1:25.

Permanent Production Packers

These may run in a variety of ways and become an integral part of the casing once set. A permanent packer may run as follows:

• On wireline and set in the casing using pyrotechnics to generate the forces required to set it in the casing

Or

• On pipe and set hydraulically by the application of tubing pressure. Figure 1:26 shows an example of this type of permanent packer.

NOTE: Both the above methods provide a disconnect mechanism from the

setting device. The setting device is removed from the well after the packer has been set. The completion string is then run into the well and a seal assembly stabbed into the polished bore of the packer.

Completion Design

Completion Design

Completion Design

Permanent packers may also be run

• Latched onto the completion tubing and hydraulically set by the application of tubing pressure.

NOTE: The tubing may be disconnected from the packer by rotation of the

latch system or by utilising an expansion joint located in the completion directly above the latch assembly.

Figure 1:27 shows an example of this type of permanent (hydro-set) packer. Permanent/Retrievable Production Packers

These packers have the same mechanical characteristics as permanent packers, but have the facility to be released and recovered from the well. These packers will not be discussed in this course.

NOTE: In general, permanent production packers can withstand much

greater differential pressures than the equivalent retrievable packer.

Completion Design

Completion Design 1.8.13 Seal Assemblies

Seal assemblies, run on tubing, packs off in the bore of a permanent packer. The sealing element frequently used is the chevron packing ring, fabricated from synthetic rubber, or from plastic such as Teflon. Seal rings are assembled in sets, facing opposite directions, to give a two-way seal. An alternative to chevron seals is the moulded rubber sleeve and in some permanent packer systems a choice of either is provided.

Figure 1:28 illustrates the assemblies available for connecting the tubing to the packer and maintaining a seal.

Locator Seal Assembly

Here the top collar or (No-Go Shoulder) locates on the bevel of the packer body, just above the left-hand thread. This type of assembly allows the tubing to set in neutral or compression.

NOTE: Seal assemblies of this type can be used without the locating collar.

Locator Seal Assemblies do not permit the tubing to be landed in tension. At most the full tubing weight can be hung off at the tubing hanger. However, when the well is producing, the temperature of the tubing will increase and the tubing will expand longitudinally. With the locator seated on the packer, and top of the tubing string fixed in the tubing hanger, expansion can take place only at the expense of buckling. By using a series of seal subs below the locator, the tubing can be pulled back a calculated distance (space-out) and then landed, leaving the locator the same distance above the packer, but with the seal assembly still within the packer bore. This will allow for tubing expansion. A completion string may also be spaced out appropriately if overall cooling of the tubing string will occur eg. in a water injection well.

Anchor Seal Assembly

This seal assembly has a latch sleeve, threaded to match the left-hand thread at the top of the packer. The lower part of the sleeve, carrying the thread, has vertical slots cut in it, and the lower flank of the thread is chamfered. On entry into the packer, the latch sleeve collapses inwards, and then springs out to engage the thread of the packer. The anchor seal assembly permits the tubing to be landed in compression, neutral, or tension. The anchor seal assembly can be released from the permanent packer by pulling the tubing in slight tension and rotating the tubing right-handed at surface. The latching sleeve will back out of the packer.

Polished Bore Receptacles (PBRs)

These are usually anchor latched to a hydro-set packer and run in the well in the closed position (shear ringed, shear pinned, J-slotted). After the packer is set, the PBR may be spaced out appropriately. A PBR affords maximum flow capability through the packer and allows a method of disconnecting from the packer for workover operation.

Tubing Seal Receptacles (TSRs)

These are usually anchor latched to a hydro-set packer and run in the well in the closed position (shear ringed, shear pinned, J-slotted). After the packer is set, the TSR may be spaced out appropriately. A TSR affords maximum flow capability through the packer and allows a method of disconnecting from the packer for workover operation. A TSR affords protection to the seals. Also, a TSR may be manufactured with circulation ports on the inner mandrel.

Completion Design

Completion Design

Completion Design