Summary
Gas wells in low-permeability formations usually require hydraulic
fracturing to be commercially viable. Pressure transient analysis in
hydraulically fractured tight gas wells is commonly based on analysis of three
flow regimes: bilinear, linear, and pseudoradial. Without the presence of
pseudoradial flow, neither reservoir permeability nor fracture half-length can
be independently estimated. In practice, as pseudoradial flow is often absent,
the resulting estimation is uncertain and unreliable. On the other hand,
elliptical flow, which exists between linear flow and pseudoradial flow, is of
long duration (typically months to years). We can acquire much rate and
pressure data during this flow regime, but no practical well test analysis
technique is currently available to interpret these data.
This paper presents a new approach to reliably estimate reservoir and
hydraulic fracture properties from analysis of pressure data obtained during
the elliptical flow period. The method is applicable to estimate fracture
half-length, formation permeability, and skin factor independently for both
infinite- and finite-conductivity fractures. It is iterative and features rapid
convergence. The method can estimate formation permeability when pseudoradial
flow does not exist. Coupled with stable deconvolution technology, which
converts variable production-rate and pressure measurements into an equivalent
constant-rate pressure drawdown test, this method can provide fracture-property
estimates from readily available, noisy production data. We present synthetic
and field examples to illustrate the procedures and demonstrate the validity
and applicability of the proposed approach.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
5 December 2006
- Meeting paper published:
29 January 2007
- Revised manuscript received:
3 June 2008
- Manuscript approved:
10 July 2008
- Published online:
15 April 2009
- Version of record:
15 April 2009
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