A new expandable wellbore casing could prove to be a boon to small-hole drilling. It is the first expandable casing designed to work economically in boreholes with diameters smaller than 4 inches.
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 prove to be a boon to small-hole drilling. This is the first
expandable casing that can be designed to work economically in boreholes with
diameters smaller than 4 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 costs and improve operations in the shallow-gas and
petroleum industries, 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 also should
find this technology useful.
Existing technology has limitations with extrusion (expansion) in
small-diameter holes, but the new self-expanding split-tube design nowworks
ably in them. A significant 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. And 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 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, an Office of
Fossil Energy effort begun in 2005 to reduce the costs and environmental impact
of shallow-gas and petroleum gas well-drilling, and to make possible the
economical development of the vast untapped reserves that exist in America’s
declining or depleted reservoirs.
Microhole technologies also are 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 Web
site at www.fossil.energy.gov.
ND