Meeting Economic Challenges of Deepwater Drilling With Expandable Tubular Technology
Expandable-tubular technology involves a process that expands casing in oil wells drilled in especially challenging environments, such as deepwater. Until now, operators have had to use progressively smallerdiameter pipe as a well was drilled deeper; but expandable-tubular goods are designed for reducing well tapering while preserving bore-hole size. The ability to expand casing in situ enables hole-size maintenance and conservation of internal casing diameter for increased efficiency; therefore operators are less likely to run out of hole diameter before evaluating all potential pay zones. They can now drill smaller holes while drilling deeper to access untapped reserves and still end up with larger casing sizes to produce at higher rates than are currently practical. In brief, the technology applies to the design and construction of oil and gas wells to • drill deeper vertical and farther extended-reach deviated wells • access reservoirs unreachable economically with other available technology • rejuvenate old wellbores by cladding expandable casing inside existing holes to increase burst rating or repair casing damage • allow the running of larger-diameter production tubulars at total depth (TD) without increasing the casing sizes used at spud One of the first applications for expandable systems is deepwater drilling. Deep, directional, horizontal, and extended-reach drilling continually create demand for more efficient tubular-goods use. Hole-size conservation is most critical in environments of high hydrostatic pressure that exist at spud depth and progressively rise immediately below it. Expandable-tubular systems enable operators to drill high-risk, high-reward, deepwater wells in uncertain areas, especially those with marginal pore pressures and fracture gradients. The technology reduces the tapering effect typical of conventional deepwater drilling and, therefore, enables operators to drill deeper and more efficiently. The decreased number and sizes of concentric pipe strings needed to equip wells increases the potential for lower drilling and production costs. Conservation and better use of downhole space give expandable-tubular systems their greatest advantage: the potential for development of oil and gas reservoirs not economically exploitable by current field methods. Expandable-tubular technology is a particularly interesting and promising field of engineering research and development. A 13 3/8- × 16-in. expandable-tubular system has been designed, built, and tested. This system will enable operators to save a casing string by extending their 16-in. shoe across a lost-circulation zone that usually occurs within 500 to 1,000 ft of drill out in the deepwater. This paper discusses known and potential deepwater applications of the technology. The paper presents the design, summarizes the testing that has been performed to date, including full-scale rig-handling tests, and discusses operational considerations associated with installation of expandable-tubular systems and the 13 3/8- × 16-in. system in particular.