Time‐lapse CSEM analysis of a shaly sandstone simulated by comprehensive petro‐electric modeling

Abstract

We simulate a poorly consolidated shaly sandstone reservoir model representing a prograding near‐shore zone geological pattern. To account for the spatial distribution of petrophysical properties, an effective porosity model is first simulated by Gaussian geostatistics. Dispersed clay and dual water models are then efficiently combined with other well‐known theoretical and experimental petrophysical correlations to consistently simulate reservoir model parameters. Next, the constructed reservoir model is subjected to numerical simulation of multi‐phase fluid flow to replicate a waterflooding scenario on a black oil reservoir and to predict the spatial distributions of fluid pressure and saturation. Finally, a modified Archie's equation for shaly sandstones is utilized to simulate rock resistivity. As a result, the comprehensive petro‐electric model developed in this paper can be efficiently utilized in sensitivity analyses of CSEM (controlled‐source electromagnetic) data to petrophysical properties and, ultimately, applied to reservoir characterization and monitoring research. As an example, we choose to present a time‐lapse frequency domain CSEM feasibility study over the 2D reservoir model embedded in a 1D background resistivity model. Three sets of marine 2.5D CSEM data are simulated by a parallel adaptive finite element algorithm. Our analysis demonstrates that a detectable time‐lapse signal after 5 years and a strong time‐lapse signal after 10 years of waterflooding are attainable using the current CSEM technology.