MORGANTOWN, W. Va. –Under the auspices of the U.S. Department of Energy’s Natural Gas and Oil Program, a cost-shared project led by Dynamic Tubular Systems Inc. has successfully completed all essential steps in developing an innovative expandable wellbore casing that could revolutionize small-hole drilling. This is the first and only expandable casing that can be designed to work economically in boreholes with diameters smaller than 4½ inches, and it has the potential to become the first expandable casing capable of protecting coiled-tubing drilling systems from harsh drilling conditions.
The new wellbore casing is expected to benefit a variety of extraction industries where it could extend the reach of traditional telescoping wellbore designs that sometimes “run out of hole” and fall short of target. The casing has great potential to reduce cost and improve operations in petroleum industry areas, including remedial work and patches for well repair, and recovery of bypassed and stranded resources, unconventional resources, and coalbed methane. Environmental, civil, and mineral extraction fields should also find this technology useful.
Existing technology has limitations with extrusion (expansion) in small-diameter holes, but the new self-expanding split-tube design works ably in them. A great advantage is that the expandable casing can be controlled to create a high-pressure mechanical seal of the drill hole in lieu of cement. This is important because cementing is difficult to perform reliably in small-diameter wells since they typically have minimal clearance between the casing and borehole; unexpected difficulties often arise, making the cost of cementing the most expensive item in a drilling project and rendering the small diameter hole uneconomical.
Development of the expandable casing progressed from initial concept to demonstration in just 2 years and has attracted industry interest as an affordable approach for maintaining borehole stability and well control. The project was supported by the Microhole Technology Initiative, an Office of Fossil Energy effort begun in 2005 to reduce the costs and environmental impact of oil and gas well-drilling and to make possible the economical development of the vast untapped oil and gas reserves that exist in America’s declining or depleted reservoirs.
The United States has an estimated 218 billion barrels of conventional oil that is unrecoverable with current technology. Recovering just 10 percent of this amount would equal about 10 years of OPEC oil imports at current rates. Microhole drilling—using supporting technologies developed through the Microhole Technology Initiative, such as the self-expanding wellbore casing—has the potential to unlock these and many other deposits currently uneconomical to extract.
Microhole technologies are also being pursued for their potential value to applications such as drilling shallow development wells, drilling reservoir data monitoring holes, drilling shallow re-entry wells, and lateral drilling from deep exploration holes. Microholes are projected to reduce drilling wastes by 20 percent and reduce overall field development costs by around 50 percent compared to conventional wells.
The Microhole Technology Initiative is managed by the National Energy Technology Laboratory. For more information about the initiative, please visit the Office of Fossil Energy’s Microhole Systems Research and Development (R&D) website.