Injection and falloff test analysis to estimate properties of unsaturated fractures
A new technique for calculating hydraulic properties of unsaturated fractured formations is proposed as an alternative to the common approach involving steady-state analysis of multi-rate gas injection tests. This method is based on graphical analysis of transient pressure data from an injection-falloff test sequence. Flow in a fracture of limited lateral extent, bounded above and below by an impermeable matrix, and intersected by a cylindrical borehole is described by two analytical models. The first model corresponds to early-time infinite acting radial flow, and the second to late-time linear flow. Interpretive equations are derived for computing fracture conductivity and volumetric aperture from early-time data, and fracture width from late-time data. Effects of fracture inclination and gravity are studied numerically, and found to be practically negligible for gas as well as water injection. Analysis of simulated injection-falloff tests using the suggested procedure yields results that agree well with simulator input values. 13 refs., 5 figs.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6967945
- Report Number(s):
- LBL-22102; CONF-861220-9; ON: DE88009831
- Country of Publication:
- United States
- Language:
- English
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