Summary
On occasion, a hydraulically fractured tight-gas well does not perform up to
its potential because of slow or incomplete fracture-fluid cleanup. A number of
papers have been written to address individual factors related to
fracture-fluid cleanup, but many questions as to which factors mostly affect
gas production from such wells remain unanswered. Numerical reservoir
simulation is one of the best methods to study the fracture-fluid-cleanup
problem. Continuing from our previous publication (Wang et al. 2008) on the
effect of gel damage on fracture cleanup, we used reservoir simulation to
analyze systematically the factors that affect fracture-fluid cleanup and gas
recovery from tight-gas wells.
We first developed a comprehensive data set for typical tight gas reservoirs
and then ran single-phase-flow cases for each reservoir and fracture scenario
to establish the idealized base-case gas recovery. We then systematically
evaluated the following factors: multiphase gas and water flow, proppant
crushing, polymer filter cake, and, finally, yield stress of concentrated gel
in the fracture. The gel in the fracture is concentrated because of fluid
leakoff during the fracture treatment. We evaluated these factors additively in
the order listed. We found that the most important factor that reduces
fracture-fluid cleanup and gas recovery is the gel strength of the fluid that
remains in the fracture at the end of the treatment.
This paper illustrates the complexity of the fracture-fluid-cleanup problem
and points out the need to use reservoir simulation and to include all the
pertinent factors to model fracture-fluid cleanup rigorously. The procedures
presented can provide a useful, systematic guide to engineers in conducting a
numerical simulation study of fracture-fluid cleanup.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
12 November 2008
- Meeting paper published:
20 January 2009
- Revised manuscript received:
19 August 2009
- Manuscript approved:
12 September 2009
- Published online:
28 April 2010
- Version of record:
22 September 2010
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