Tie-Back Packer

A tie-back packer is a sealing device used in well completions to connect a new section of casing or tubing back to a section already in place. The most common application is reconnecting an upper casing string to a previously installed liner that was hung off below it. The tie-back packer creates a pressure-tight seal between the new tieback string and the existing liner, restoring full-bore pressure isolation in the well. It is a specialty packer, not a routine production packer, and it shows up most often in liner-extension workovers, well-deepening jobs, and certain sidetrack completions where a new wellbore needs to share the lower portion of an existing one.

Key Takeaways

A tie-back packer connects a new casing or tubing string to an existing liner in the well, sealing the connection point against pressure from above and below. The seal lets the operator extend a liner up to surface or to a different setting depth without having to redrill the lower section.
The most common context is the tie-back of a production liner to surface. A liner is a casing string that hangs from a previous casing shoe rather than running all the way to surface. After the well is drilled and completed, the operator may decide to convert the liner into a full-bore casing by tying it back. The tie-back packer is the seal at the top of the original liner where the new string attaches.
Tie-back packers can be set mechanically (using rotation or weight applied from surface), hydraulically (by pumping pressure into the work string), or by setting tools (a separate setting tool deployed on wireline or coiled tubing). Each setting method has cost and reliability trade-offs depending on the well configuration.
The seal element is typically an elastomer (HNBR, FKM, or AFLAS depending on temperature and chemical exposure) that compresses against the inside of the existing liner. Modern HPHT tie-back packers use metal-to-metal sealing in addition to or in place of elastomer for high-temperature service above 200 degrees Celsius.
Tie-back failures can be expensive. A leaking tie-back packer admits annular fluid into the production string, contaminates production, and can require a complete pull-and-reset of the upper string. The remediation cost on a deep well is typically CAD 800,000 to CAD 3 million depending on depth and rig type.

Fast Facts

Some of the deepest tie-back operations in the world take place in the deepwater Gulf of Mexico, where production liners hung at 25,000 feet (7,620 metres) are regularly tied back to floating production facilities through 5,000 feet of water column plus the upper wellbore. The tie-back packer at the top of the production liner has to seal against pressures over 15,000 psi at temperatures over 150 degrees Celsius for the producing life of the well, which can be 25 years or more. A single tie-back failure on one of these wells can shut in 20,000 barrels per day of production, making the integrity of this small piece of completion hardware disproportionately important.

What a Tie-Back Packer Does, Explained

Picture two pieces of pipe, one above the other in a well, that need to be joined into a single sealed conduit. The lower pipe (a liner) was installed first, hung from a hanger at its top. The upper pipe (the tieback) is being installed later. At the joint between the two, the upper pipe needs to land cleanly into a profile inside the top of the lower pipe, and the joint needs to seal against pressure from the well below and pressure from the annulus around it.

The tie-back packer is the sealing element at that joint. It sits on the bottom of the upper string and lands into a polished bore receptacle (PBR) at the top of the lower string. When set, the packer's seal element compresses against the inside surface of the receptacle, creating a pressure-tight connection. The upper string can now be pressure-tested as a complete unit, and the well can be put on production.

Where Tie-Back Packers Are Used

The standard case is a liner tieback after the lower well has been completed. The operator originally drilled the lower section, hung a production liner across the reservoir interval, and produced through a tubing string that landed in a separate seal bore. After several years of production, the operator decides to convert the well configuration: pull the tubing, install a tieback to extend the liner up to surface as a full-bore casing, then run new tubing through the longer cased hole. The tie-back packer is the connection at the top of the original liner.

Sidetrack completions are another use case. When an existing well needs to be sidetracked (drilled in a new direction from a higher kickoff point), the operator drills the new wellbore down to the new target. The new well's casing has to tie back to the existing casing at the kickoff point. A tie-back packer at the junction creates the pressure seal between the old and new wellbores.

Well-abandonment programs sometimes use tie-back packers as part of the plug-and-abandonment design. A tieback can isolate a deeper section of the well that contains a producing or potentially producing reservoir, allowing the upper section to be abandoned cleanly while preserving the option to re-enter the lower section in the future.

A tie-back packer is also called a tieback seal, tieback assembly, or liner tieback packer. The corresponding receptacle in the lower string is called a polished bore receptacle (PBR), tieback nipple, or seal bore. Related terms include liner (a casing string that hangs from the previous casing shoe rather than running to surface; the lower string that a tie-back packer attaches to), packer (a sealing device used to isolate sections of a wellbore; the broader category that includes tie-back packers, production packers, and various specialty types), polished bore receptacle (PBR, the smooth-walled internal section at the top of a liner where a tie-back packer or production seal lands; the mating surface for the packer's seal element), casing (the steel pipe cemented into a wellbore to prevent collapse and isolate formations; tie-back operations extend a liner into the role of a full-bore casing string), and sidetrack (a new wellbore drilled from a kickoff point above the bottom of an existing well; tie-back packers are used to seal the junction between the original and sidetracked sections).

Why a Small Seal Holds the Whole Well Together

A semisubmersible drilling rig in the Norwegian Continental Shelf is finishing a deepwater appraisal well. The well was drilled with a production liner hung at 4,200 metres total depth. The completion design calls for tying the liner back to the wellhead at the seabed using a 7-inch tieback string. The tie-back packer sits at the top of the production liner, 4,150 metres below the seabed and 5,500 metres below the rig.

The tieback string is run on the drillpipe, the packer is landed in the polished bore receptacle, and a setting tool applies hydraulic pressure to compress the elastomer seal element against the receptacle wall. The pressure test reads 12,000 psi held for 30 minutes with no decay. The tieback is sealed.

The well is then completed and put on production. For the next 18 years, the small elastomer seal at the top of that liner holds the produced fluids inside the tieback string and out of the annulus, allowing the well to produce 14,000 barrels per day cleanly. A failure of that seal at any point in those 18 years would have meant pulling the entire tieback string, replacing the packer, and re-running everything: a USD 12 to 18 million workover. The seal does not fail. The job is done. A piece of hardware roughly the size of a soccer ball, sitting two and a half miles below the rig floor, is what keeps the well economically viable for almost two decades.