How to Infer Porosity from Seismic Data by Using Effective Medium Modeling? A Case Study in the Fort Worth Basin

Abstract

Many geophysical studies in reservoir characterization focus on the variations in the elastic properties of rocks. They commonly involve seismic data, which are processed in terms of seismic attributes. These processed data still have to be related to the physical properties of the rock mass and the fluids saturating the pore space. This need motivated the development of research projects referring to the effective medium theory (EMT). In the present, we refer to EMT to infer porosity data from seismic impedances within a fractured reservoir. The leading idea is to take advantage of the available impedances to characterize the spherical porosity and the crack density. We develop an effective medium model that provides numerical responses for seismic impedances. These responses are then compared to the impedances obtained from stratigraphic inversion. The overall procedure consists in adjusting the input parameters of the EMT model, which are spherical porosity and crack density, to minimize the impedance mismatch. Our case study concerns the limestone formations of the Fort Worth Basin (Marble Falls and Ellenburger formation). Results are promising and the EMT could be a very useful tool to explain reservoir and geophysical data in terms of microstructural properties, in particular for fractured reservoirs.