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One of the most exciting developments in the last decade has been expandable tubulars because they offer the potential for a "monoborehole" and drilling to depths no longer limited by initial hole diameter. As a result, the focus on tubulars has concentrated on expandable casing.
Monodiameter borehole concept
A key development is the concept of the monodiameter borehole (Fig. 1). Production casing can be run inside the expanded form of casing with the same diameter with this concept. It will allow, for the first time, casing to be set at will or as needed without a penalty in completed depth. Lost-circulation zones, swelling shales, and other drilling problems can be put behind pipe as necessary without jeopardizing planned total depth. Total depth limitations will now be limited primarily to mechanical capabilities of the drill rig, casing, and/or drillpipe run into and out of the borehole.
Elastomers on the exterior of the expanded casing have proved to be effective pressure seals in liner lap applications in lieu of running a conventional liner hanger seal assembly. Additional testing for sealing potential is being conducted. Field tests are planned to investigate the potential of expandable casing to seal off against the formation without cement. If the test is successful, it will demonstrate the potential to eliminate most cementing operations, one of the costliest phases of well construction. If this becomes an accepted, safe practice, it could enable other opportunities for unprecedented reductions in exploration cost.
Noteworthy papers in OnePetro
Rune Gusevik, Randy Merritt 2002. Reaching Deep Reservoir Targets Using Solid Expandable Tubulars, SPE Annual Technical Conference and Exhibition, 29 September-2 October. 77612-MS. http://dx.doi.org/10.2118/77612-MS.
Roger van Noort et al. 2002. Using Solid Expandable Tubulars for Openhole Water Shutoff, Abu Dhabi International Petroleum Exhibition and Conference, 13-16 October. 78495-MS. http://dx.doi.org/10.2118/78495-MS