Summary
Slickwater fracturing has been increasingly applied to stimulate
unconventional shale-gas reservoirs. Comparing with crosslinked fluids,
slickwater used as a fracturing fluid has several advantages, including low
cost, a higher possibility of creating complex fracture networks, less
formation damage, and ease of cleanup. An enormous amount of water is injected
into the formation during the treatment. Even with a good recovery of injected
water from flowback, large quantities of water are still left within the
reservoir.
The dynamics of the water phase within the created hydraulic fractures and
reactivated natural fractures (induced fractures) has significant impact on
both short- and long-term performance of a hydraulically fractured well. The
dynamics of the water phase within fractures is controlled by many mechanisms,
such as relative permeability, capillary pressure, gravity segregation, and
stress-sensitive fracture conductivities. In this paper, reservoir-simulation
models for a generic gas-shale reservoir are constructed to investigate the
changes of water-saturation distribution in fractures over time during
production and their impact on gas-production performance. It is demonstrated
that water imbibitions caused by capillary pressure and gravity segregation can
play important roles in water-saturation distribution and redistribution,
particularly during extended shut-in, which in turn affects gas flow
significantly. Moreover, an unfavorable combination of relative permeability,
capillary pressure, stress-sensitive fracture conductivities, and invasion-zone
permeability damage can lead to water-blockage problems.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
3 September 2010
- Meeting paper published:
10 February 2010
- Revised manuscript received:
29 May 2011
- Manuscript approved:
8 September 2011
- Published online:
27 February 2012
- Version of record:
14 March 2012
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