This paper describes a new analysis technique for determining vertical permeability from pressure buildup data in partially-perforated wells. The method applies when the vertical permeability is low enough that the Horner straight-line region characteristic of the perforated interval exists. A correlation chart is presented that relates the vertical permeability to the dimensionless pressure group (P* " Pi)/m, the percent completion, and a dimensionless time based on the flow duration, rock and fluid properties, and the thickness of the perforated interval. The variable m is the slope of the straight line corresponding to the perforated interval, p* is the extrapolation of this line to infinite shut-in time, and p,- is the initial reservoir pressure. Two simulated pressure buildup responses are presented and discussed to illustrate the technique.

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