Flow tests are conducted for oil well in reservoirs P, Q, R and S having different parameters as given in the following table. In all the four cases the wells are tested at 1200 stb/day. Identify the reservoir in which the pressure transient reaches earliest at a point 2000 ft away from the wellbore.
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When analyzing pressure transients, prioritize reservoirs with higher permeability and smaller wellbore radius for faster pressure responses.
Step 1: Understand the factors affecting pressure transient.
The pressure transient in a reservoir is influenced by permeability, oil viscosity, total compressibility, wellbore radius, and pay zone thickness. Generally, higher permeability and lower viscosity will result in faster pressure transients.
Step 2: Analyze the given parameters for each reservoir.
- Reservoir P: High permeability (100 mD) and moderate porosity (23%), but a small wellbore radius (0.5 ft) and relatively low pay zone thickness (10 ft).
- Reservoir Q: Moderate permeability (50 mD) and porosity (21%), but higher oil viscosity (1.1 cP) and smaller wellbore radius (0.4 ft).
- Reservoir R: High permeability (150 mD) and porosity (25%), with moderate oil viscosity (0.9 cP) and the smallest wellbore radius (0.3 ft).
- Reservoir S: High permeability (170 mD) and porosity (28%), with moderate oil viscosity (1.0 cP), but the largest wellbore radius (0.6 ft) and the thickest pay zone (20 ft).
Step 3: Conclusion.
Reservoir R, with the highest permeability and moderate oil viscosity, is expected to have the earliest pressure transient response. The relatively small wellbore radius (0.3 ft) ensures that pressure transients occur faster than in reservoirs with larger radii.
Thus, the correct answer is (C) R.
