Prefracture testing in tight gas reservoirs
A pressure transient test run before a fracture job in a tight gas reservoir is an invaluable part of the total testing program necessary to evaluate the efficacy of such a fracture job. This paper addresses the problem of treating the pressure-sensitive viscosity/compresssibility (..mu..c/sub t/) product while analyzing the prefracture test data. A large variation of ..mu..c/sub t/ with pressure occurs in a typical low-flow-capacity (kh) well. These pressure-sensitive gas properties lead to a nonlinear gas flow equation. Use of pseudopressure function partially linearizes the gas flow equation, while introduction of pseudotime and pseudopressure causes the complete linearization. This linearization permits a valid type-curve analysis. However, a semianalytical solution of the diffusivity equation that considers only the pseudopressure function suggests that the problem of nonlinearity is insignificant. The authors show that both the contentions presented in the literature are correct: complete linearization is required when the data are affected by wellbore storage, whereas partial linearization is quite adequate for a valid semilog analysis. Large variations of the ..mu..c/sub t/ product also cause the wellbore storage to last a long time, even in the presence of a downhole shut-in tool. They demonstrate that the convolution approach, for which the sandface rate measurement is required, shortens the testing time by orders of magnitude and yields the desired formation parameters of kh and skin.
- Research Organization:
- Schlumberger Technical Services Inc.
- OSTI ID:
- 5603249
- Journal Information:
- SPE (Society of Petroleum Engineers) Format. Eval.; (United States), Journal Name: SPE (Society of Petroleum Engineers) Format. Eval.; (United States) Vol. 1:2; ISSN SFEVE
- Country of Publication:
- United States
- Language:
- English
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Prefracture testing in tight gas reservoirs
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ANALYTICAL SOLUTION
COMMINUTION
COMPRESSIBILITY
DATA ANALYSIS
DIFFUSION
ENERGY SOURCES
ENHANCED RECOVERY
EQUATIONS
EQUIPMENT
FLOW RATE
FLUID FLOW
FLUIDS
FORMATION DAMAGE
FOSSIL FUELS
FRACTURING
FUEL GAS
FUELS
FUNCTIONS
GAS FLOW
GAS FUELS
GASES
HYDRAULIC FRACTURING
MECHANICAL PROPERTIES
NATURAL GAS
NATURAL GAS WELLS
NONLINEAR PROBLEMS
PERFORMANCE TESTING
PERMEABILITY
PRESSURE DEPENDENCE
PRESSURE MEASUREMENT
RECOVERY
RESERVOIR PRESSURE
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
STIMULATION
TESTING
VISCOSITY
WELL LOGGING
WELL LOGGING EQUIPMENT
WELL PRESSURE
WELL STIMULATION
WELLS