Summary
Many shale gas reservoirs have been previously thought of as source rocks,
but the industry now finds these source rocks still contain large volumes of
natural gas and liquids that can be produced using horizontal drilling and
hydraulic fracturing. However, one of the most uncertain aspects of shale gas
development is our ability to accurately forecast gas resources and shale gas
development economics. The uncertainty of the problem begs for a probabilistic
solution.
The objective of our work was to develop the data sets, methodology and
tools to determine values of original gas in place (OGIP), technically
recoverable resources (TRR), recovery factor (RF) and economic viability in
highly uncertain and risky shale gas reservoirs. Existing approaches for
determining values of TRR, such as the use of decline curves or even volumetric
analyses, may not be reliable during early time because there may not be enough
production history for decline curves to work well or the uncertainty in the
reservoir properties may be too large for volumetric analyses to be useful.
To achieve our research objective, we developed a computer program,
Unconventional Gas Resource Assessment System (UGRAS). In the program, we
integrated Monte Carlo technique with an analytical reservoir simulator to
estimate the original volume in place, predict production performance and
estimate the fraction of TRR that are economically recoverable resources (ERR)
for a variety of economic situations. We applied UGRAS to dry gas wells in the
Barnett Shale and the Eagle Ford shale to determine the probabilistic
distribution of their resource potential and economic viability. Based on our
assumptions, the Eagle Ford shale in the dry gas portion of the play has more
technically recoverable resources than the Barnett shale. However, the Eagle
Ford shale is currently not as profitable as the Barnett shale because of the
higher drilling costs in the Eagle Ford dry gas window.
We anticipate that the tools and methodologies developed in this work will
be applicable to any shale gas reservoir that has sufficient data available.
These tools should ultimately be able to allow determination of technically and
economically recoverable resources from shale gas reservoirs globally.
© 2013. Society of Petroleum Engineers
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History
- Original manuscript received:
9 February 2012
- Meeting paper published:
6 February 2012
- Revised manuscript received:
30 October 2012
- Manuscript approved:
3 December 2012
- Published online:
1 February 2013
- Version of record:
1 February 2013
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