Following the introduction of expandable tubular technology, an impressive list of applications emerged, starting with the universally desirable monobore completion.
With an optimized well bore, defined as one with the largest possible inside diameter, operators have been presented with a multitude of completion and production choices. Many of these options were not possible in wells constructed using standard API tubular size progressions. This was particularly true in wells that encountered unexpected problems while drilling, forcing the operator to set an unplanned liner or protection string. Dropping a full API size could wipe out the possibility of using certain completion options, or at the very least limit the number of options considerably.

Unequaled versatility of SET Systems provides a wide variety of easily-implemented solutions to typical well problems (red).



Well problems seldom occur as isolated incidents. For example, the lost circulation problem that an operator might solve by setting a protection string could be the harbinger of deep formation damage in the pay zone. One solution for deep formation damage is to use deep-penetrating perforation charges, but “Oh-oh!” the liner that solved the lost circulation problem is too small to accommodate the larger perforating guns needed to reach beyond the damaged zone.

Necessity remains the mother of invention

Current energy economics demand that operators try to get the most out of every well they drill. And technology advances have kept pace with this increasing demand. Completion and production technology and techniques help improve production rates and recovery factors while at the same time providing sand and water management solutions as well as improved flow assurance. But all the solutions in the world won’t help if there’s no room to deploy them. Expandable tubulars can provide that room.

Although multizone completions have been around for a long time, they have undergone a major renaissance with the advent of unconventional gas plays. Operators that considered dual completions as cutting-edge technology a few decades ago now think nothing of performing a 15-stage hydraulic fracture treatment in
a single horizontal well bore.

Comparison of conventional liner with swellable packers versus SET System in openhole completion illustrates increased inside diameter benefits of expandables, leaving more room for deployment of completion hardware.



But to effectively perform multistage fracturing jobs requires hydraulic isolation for each stage and the ability to convey large volumes of frac fluid at high rates to propagate the fractures for maximum reservoir contact. Pumping these treatments through small-diameter tubulars, often the result of problems during the drilling phase, limits their effectiveness and drives up costs.

The list of advantages provided by expandable tubulars used in new well multizone completions is impressive:
• Allows largest possible well bore, largest diameter coiled tubing, largest perforating guns, fastest post-frac cleanout.
• Reduces tubular friction, lowers frac horsepower requirements;
• Provides unlimited number of stages treated per trip.
• Enhances zonal isolation over that provided by conventional liners with swellable seals or conventional packers.
• Can reduce rig time by reducing number of trips into the well.
• No mechanical complexity such as frac sleeves or multicomponent packers.
• Leaves a full diameter thru-bore. No nipples to drill out.
• No cementing required.

Applications list grows exponentially

The number of potential applications for expandable tubular technology is growing by leaps and bounds, largely due to its ability to solve a multitude
of issues in an elegant way. Not a quick-fix approach intended only to solve unexpected well problems, expandables are being cited in well construction plans.

Nowhere are these solutions more beneficial than in re-entry work or re-fracturing programs. Because of near-universal applications and their ability to adapt to any diameter, solid expandables are ideal for field rejuvenation programs. A wide variety of workover activities can be achieved successfully and economically.

One of the most popular applications for expandable technology is restoring wellbore integrity, either by repairing damaged or split casing or by sealing off perforations. Sections of casing weakened by wear, erosion or corrosion can be restored to their original pressure ratings by cladding using an expandable liner. Water or sand ingress can be curbed by cladding across old perforations or ineffective sand control media with little loss of inside diameter.

Expandables can even be used in the open hole to bridge across unstable sections, facilitate branch laterals or sidetracks by providing an effective, maximum-diameter liner in the build section, or as an easy-to-set isolation plug.

Production optimization applications beckon

Perhaps among the most interesting recent applications for expandable technology is in re-completions, especially in re-frac treatments. In the many shale gas plays around North America, operators are finding that they can dramatically increase their recovery factors by sealing off depleted fractures and re-fracing new, untreated sections of the reservoir. Of course, this can be done conventionally using packers and liners, but not without giving up considerable inside diameter in the process. In a well originally completed with 51?2-in. casing, for example, it doesn’t take too many liners to run out of room in the well bore long before the reservoir runs out of gas.

Compare a conventional re-frac job performed in 51?2-in., 17 lb/ft casing. Inside diameter (ID) of the casing is 4.892 in. and drift ID is 4.767 in. That means that, allowing for isolation with swellable packer material, the largest conventional liner that can be run in the well would be 31?2-in., 9.3 lb/ft casing with a 2.992-in. drift ID. Assuming that the liner can be run successfully, then the operator must wait five to 10 days for the packer material to swell and seal off the annulus so the new zones can be perforated and treated.

The same job performed with an expandable system could use a 4.25-by 5.50-in. FracSET ReFrac liner that, when fully expanded and sealed would leave an ID of 4.21 in. — plenty of room to get large guns and coiled tubing into the well to perform the re-frac job. Because compression is put into the seal material when the liner is expanded, there is no delay waiting on the swellable. The well could even undergo a second re-frac treatment using a 4- by 5-in. ReFrac liner with an ID of 3.465 in. — as opposed to the 2.992-in. ID of the conventional single re-treat job.

Figure 2 shows the comparison between conventional 41?2-in. liner with swellable seals and a MaxFrac 51?2- by 7-in. FracSET liner in a 61?4-in. open hole.

Two types of FracSET liners are available — fully expandable and partially expandable. The fully expandable liner, as its description implies, expands across its entire length. The partially expandable liner has expandable isolation anchors at each end to seal and anchor the liner, but the intervening length of liner is not expanded. Either system can be enhanced by installing swellable or bonded seals at intervals to isolate old perforations and new frac zones. Installation of either system is fast and results in a larger drift ID of the completion compared with any other technique except squeeze cementing, which has limitations and adds considerable risk.

The system is both efficient and versatile. Long continuous clads can be installed in a few hours on a single trip. An unlimited number of isolation points can be preplanned by installing swellable external seals at the required intervals in the field before running the liner into the hole. Short or long perforation clusters can be accommodated with ease. And standard completion tools and deployment techniques such as pump-down assemblies, tractors, coiled tubing, high-pressure liquid jet perforators, and composite frac plugs can be used because of the added available ID.

Long-term profitability enabled

With their operational flexibility and deployment efficiency, expandable techniques offer an economic solution to the challenge of improving reservoir productivity and life. In years past, about the only available technique to improve production was to drill infill wells. This was largely due to the limited number of options imposed by conventionally-completed wells. After the first workover, there was no more room to do anything except attempt a costly clean-out program that
often damaged the original tubulars. Squeezing off old perforations and re-completing by re-perforating and treating different zones was problematic and often resulted in loss of hydraulic isolation compromising success of the re-treatment. Many times a company will re-enter an old well only to find out there are myriad well integrity problems that must be resolved before a re-treatment can be performed. A single application of an expandable can solve several of these problems at once while re-enforcing the old tubulars over the entire length where the liner is installed.

The list goes on as additional applications are conceived. Most importantly, SET Liners have minimal effect on production because of the maximum thru-bore capacity after expansion. Whether installed as a liner to facilitate a re-frac job or to enable a sidetrack into a previously undeveloped reservoir compartment, expandable technology provides the maximum number of options to improve asset productivity or extend its life.