Summary
In general, successful applications of horizontal wells have been limited to
high-permeability reservoirs and unconventional formations such as coal, chalk,
and shale. Conversely, few tight-gas-sandstone reservoirs that require
stimulation have realized sustained success with horizontal completions. One
example of such success is the Cleveland Sand of north Texas and the Oklahoma
Panhandle. Very recently, some success with horizontals has been observed in
the Bossier and Cotton Valley Sands of East Texas and north Louisiana.
Horizontal wells are commonly two to four times more expensive to drill and
complete than offset vertical wells, yet they are theoretically capable of up
to three to five times the production. Higher gas prices have lead to
potentially better economics for horizontal wells (Mulder et al. 1992).
However, research shows that in practice, many of these wells typically produce
only 10 to 30% more than offset vertical wells. With costs more than double
those of vertical wells, the economics is obviously unfavorable.
This paper discusses ways to identify and manage risks when planning,
drilling, and completing horizontal wells in tight-sandstone formations to
improve success.
Evidence has shown that shortcuts and blanket approaches do not work usually
in these completion environments. A multitude of lithological and depletion
possibilities exist as risks that need to be identified and managed through
appropriate application of integrated drilling and completion technologies.
Each risk may require different drilling and completion considerations in order
to succeed. There is simply no recipe for repeat success.
A detailed method is presented to identify, understand, and manage risk
associated with horizontal wells drilled in tight-gas-sandstone reservoirs. The
method will address all of the complex subjects that need to be considered for
the successful placement and completion of a horizontal well, including
reservoir description (both static and dynamic), well design, drilling,
stimulation, and production. It will also illustrate consequences of what may
happen if these issues are not considered properly. Through this method,
horizontal-well feasibility and economic results can be determined. If a
horizontal well has been determined to be viable economically, this method can
consistently provide a solution as to what the best completion type (vertical
or horizontal) is to recover reserves and enhance recovery efficiency in
tight-gas-sandstone reservoirs.
© 2009. Society of Petroleum Engineers
View full textPDF
(
5,407 KB
)
History
- Original manuscript received:
1 August 2007
- Meeting paper published:
11 November 2007
- Revised manuscript received:
4 August 2008
- Manuscript approved:
26 September 2008
- Published online:
1 May 2009
- Version of record:
1 May 2009
View Cart
