1. n. [Well Testing]

A flow regime that occurs when the predominant flow pattern in the reservoir is toward a point. Spherical flow occurs for partial penetration and limited-entry completions. This flow regime is recognized as a -1/2 slope in the pressure derivative on the log-log diagnostic plot. Its presence enables determination of the spherical permeability. When spherical flow is followed by radial flow, both horizontal and vertical permeability can be quantified.