Microhole Technology Initiative Produces Expandable Wellbore Casing

January 27, 2008 // Published as a news service by IHS

This is the first and only expandable casing that can be designed to work economically in boreholes with diameters smaller than 4 and one-half inches, and it has the potential to become the first expandable casing capable of protecting coiled-tubing drilling systems from harsh drilling conditions said NETL.

The 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 said NETL. 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 self-expanding split-tube design works ably in small-diameter holes. An advantage is that the expandable casing can be controlled to create a high-pressure mechanical seal of the drill hole in lieu of cement.

According to NETL, 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 two 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, a DOE 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 U.S. has an estimated 218B barrels of conventional oil that is unrecoverable with current technology. Recovering just 10% of this amount would equal about 10 years of Organization of Petroleum Exporting Companies (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, said NETL.

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% and reduce overall field development costs by around 50% compared to conventional wells said NETL.

The Microhole Technology Initiative is managed by NETL. More information about the initiative is available on the DOE Office of Fossil Energy's Microhole Systems R&D web site.

Source: U.S. Department of Energy (DOE) National Energy Technology Laboratory (NETL).