Capillary pressure (\(P_c\)) vs water saturation (\(S_w\)) curves for different sandstone reservoirs (I, II, III and IV) are given in the following figure. Which reservoir has the most uniform pore size distribution?
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In capillary pressure curves, a smooth and gradual curve indicates a uniform pore size distribution, while a steep curve suggests more variation in pore sizes.
Step 1: Understanding the capillary pressure curves.
Capillary pressure (\(P_c\)) vs water saturation (\(S_w\)) curves describe how capillary pressure changes with the water saturation of the pore spaces in a reservoir. These curves are used to infer the pore size distribution and other reservoir characteristics.
Step 2: Pore size distribution interpretation.
The uniformity of the pore size distribution is indicated by how smoothly the \(P_c\) curve behaves. A more uniform distribution corresponds to a smoother and more gradual curve.
Step 3: Evaluating the curves.
- (A) I: The curve shows a steep gradient, indicating a heterogeneous pore size distribution.
- (B) II: The curve is less steep but still shows some variability in pore sizes.
- (C) III: The curve indicates a moderate variation in pore sizes, though less than I and II.
- (D) IV: The curve is smooth and gradual, indicating a very uniform pore size distribution. This is the characteristic of reservoir IV.
Step 4: Conclusion.
The reservoir with the most uniform pore size distribution is represented by curve IV. Therefore, the correct answer is (D).
