Average Reservoir Pressure Estimates in a Commingled Reservoir

Abstract

SummaryLate-transient buildup responses at a well that produces a two-layer reservoir with no-crossflow are studied. The well is located at the center of a circle and the outer boundaries are assumed to be impermeable. The initial pressure is identical in each layer. Our emphasis is on the determination of average reservoir pressure. This study provides (i) a complete description of the buildup trace following the initial-transient period (or the semilog straight line should it exist) by obtaining analytical expressions that highlight the influence of the variables that affect the trace, (ii) a physical interpretation for the value of pressure that corresponds to the level portion of the buildup curve, (iii) an interpretation of average pressure estimate obtained by using the Matthews-Brons-Hazebroek functions for single-layer systems (in this regard a number of insights are provided), (iv) a theoretical justification for the application of the Muskat and the Arps-Smith methods to estimate average reservoir pressure, and (v) a direct method to compute average reservoir pressure. Results are extended to multilayer systems.