Prefracture Testing in Tight Gas Resevoirs
A pressure transient test run prior to a frac job in a tight gas reservoir constitutes an invaluable segment of the total testing program necessary to evaluate the efficacy of such a frac job. This work addresses the problem of treating the pressure-sensitive viscosity-compressibility (..mu..c /SUB t/ ) product while analysing the transient data. The large variation of ..mu..c /SUB t/ product with pressure occurs in a typical low flow capacity (kh) well. These pressure-sensitive gas properties lead to a non-linear gas flow equation. Use of the pseudopressure function partially linearizes the gas flow equation, while introducing pseudotime and pseudo-pressure functions causes the complete linearization. This linearization permits a valid type curve analysis. However, a semi-analytical solution of the diffusivity equation considering only the pseudopressure function suggests the problem of non-linearity is insignificant. This work shows that both the contentions presented in the literature are correct: complete linearization is required when the data are affected by the afterflow, whereas partial linearization is quite adequate for a valid semilog analysis. Large variations of ..mu..c /SUB t/ product also cause the afterflow to last a long time, even in presence of a downhole shut-in tool. We demonstrate that the convolution of the afterflow data does not require a constant wellbore storage (afterflow) coefficient assumption. More importantly, the convolution approach for which the sandface rate measurement is required, shortens the testing time by orders of magnitude yielding the desired formation parameters of kh and skin.
- Research Organization:
- Schlumberger Technical Services Inc.
- OSTI ID:
- 5281879
- Report Number(s):
- CONF-8405166-
- Journal Information:
- Soc. Pet. Eng. AIME, Pap.; (United States), Journal Name: Soc. Pet. Eng. AIME, Pap.; (United States) Vol. SPE12918; ISSN SEAPA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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Plowshare-- (-1989)
COMMINUTION
EFFICIENCY
FLUID FLOW
FLUID MECHANICS
FLUIDS
FRACTURING
FRACTURING FLUIDS
GAS FLOW
HYDRAULIC FRACTURING
HYDRODYNAMICS
MECHANICS
NATURAL GAS WELLS
PRESSURE GRADIENTS
RESERVOIR PRESSURE
STIMULATION
TESTING
WELL STIMULATION
WELLS