Which flow type involves formation-to-wellbore flow channeled through a short set of perforations or a probe, with a characteristic t^-0.5 slope?

• A. Spherical Flow
• B. Radial Flow
• C. Bilinear Flow
• D. Image Wells

Answer: (A)

Flow around a short perforation or probe acts like a localized, point-like source feeding the well. The affected region grows in three dimensions, so the flow pattern is spherical rather than spreading uniformly around the entire wellbore. In this spherical near-wellbore geometry, the pressure response to a constant-rate drawdown shows a characteristic t^-0.5 decline, which is the telltale sign of spherical flow. If the flow were radial, it would imply flow all the way around the wellbore circumference; bilinear flow involves flow into a fracture plane, and image wells are a modeling construct for boundary effects, not the actual near-wellbore geometry. Thus the scenario described best matches spherical flow.