A New Derivative Type-Curve for Pressure Buildup Analysis with Boundary Effects

Abstract

This study investigates pressure buildup behavior of wells with wellbore storage and skin in bounded circular reservoirs, when inner and outer boundary effects interact to fully or partially dominate the well pressure response. Using dimensionless pressure derivative as the dependent variable, we show that early time response is governed by CDeZ and late time response by r,D2/cD . Equations are provided to estimate the limits of the intermediate time period, which corresponds to infinite acting radial flow and a semi-log straight line on a pressure-time graph. We present a new buildup derivative type curve, incorporating inner boundary (early-time) and outer boundary (late-time) effects. Applications of this type curve in buildup test design and interpretation are discussed.