A Rock Physics based Petroleum Reservoir Characterization. The Case of a West African Reservoir

Abstract

The primary variables that determine the elastic response in clastic sediments are porosity, minerology and pore fluid. However typically, only two are obtained from seismic data. As a result, resolving petroleum and gas reservoir properties in respect of seismic data is not obtainable. In order to resolve this problem a case study is presented here. The study is based on well log data derived from the West African Congo basin. A marine environment characterized by thick shale above a shaly/sand oil layer with elastic properties linked to sediment properties by the rock-physics model of Han et al. (1986). Taking into consideration the work of Thomas and Stieber (1975), a petrophysical linear link was developed based on conceptual inferences. This link is expected to serve as a means of substituting porosity for clay content and vice versa in order to resolve the underdetermined system of rock-physics equations. As a result, an inversion of reservoir elastic properties for petrophysical properties becomes obtainable. Furthermore, this work presents reservoir delineation based on Han et al (1986) model on the well log scale and later up scaled to the seismic scale.