Summary
Gas-well productivity in tight reservoirs is greatly impeded by
fracturing-fluid interactions with the formation. New simulators introduce
formation-damage mechanisms to calculate gas-well productivity. However,
equations describing formation damage must be supported by experimental data
obtained in conditions representative of fracturing operations.
The purpose of this work is to derive absolute-permeability and
multiphase-flow damages upon return gas permeability after core invasion by a
fracturing fluid by methods used in the Special Core Analysis Laboratory
(SCAL). The core permeability is in the microdarcy range with significant
illitic content. Absolute-permeability damages caused by fracturing-fluid
filtration and water sensitivity are measured. Water-saturation profiles
recorded by X-ray in two-phase-flow experiments are interpreted. The
methodology of interpretation provides the petrophysical data specific to the
rock/fluid system: absolute permeability, relative permeability damage caused
by hysteresis, and capillary pressure.
In addition, simulations are presented for the evaluation of the effect of
various operational parameters, such as pressure drawdown, on gas productivity.
It is shown that permeability hysteresis is the determinant factor to explain
low gas recoveries at short term. In the long term, the natural cleanup is very
slow. The results, derived from a real rock/fluid system, are used to provide
recommendations for improving backflow procedures. This methodology can be
applied to any case of damage caused by the alteration of rock/fluid
properties.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
9 November 2007
- Meeting paper published:
14 February 2008
- Revised manuscript received:
1 April 2009
- Manuscript approved:
9 October 2009
- Published online:
14 July 2010
- Version of record:
2 December 2010
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