A Comprehensive Pressure Distribution Model for Horizontal Well in a Gas-Cap Reservoir

Abstract

Subjecting well test data to interpretation model limits the data to capacity of the model. It is therefore necessary that pressure distribution models have all pertinent features that enhance accuracy of well test analyses. Flow regimes have been identified by the characteristic shape of their flow pattern. But the existing well test interpretation models limit the spatial orientation of these flow patterns within the three-principal axes of a reservoir. Thus, the number of flow regimes is limited. This article presents a comprehensive pressure distribution model for horizontal well in a reservoir subject to a gas cap. Pressure distribution in form of dimensionless pressure and dimensionless pressure derivatives were derived from Source and Green’s functions. Result show that, the type of flow regime that would exist and its interval of existence are determined by the architecture of the reservoir system, reservoir system parameters and the fluid properties. Additional six flow regimes, which hitherto were not considered, have been presented. Each flow regime was characterized by its flow pattern, its spatial orientation in relation to the three-principal axes, its interval of existence and characteristic signature on log-log pressure distribution plot. It was observed that boundary dominated effect of gas cap resulted in constant value of dimensionless pressure and a declining value of dimensionless pressure derivative.