Determining Reservoir and Rock Physics Parameters with a Petrophysically Coupled Joint Inversion of CSEM and AVA Data

Abstract

We consider a simple one dimensional marine gas sand model: a reservoir sand layer is buried in an encasing shale host. Using well established petrophysical relationships such as Archie’s law and Gassman’s equations, we create corresponding geophysical models of resistivity, density, P-wave velocity and S-wave velocity. From these models we calculate synthetic frequency domain marine controlled-source electromagnetic (CSEM) data and amplitude vs. angle (AVA) traces to examine a petrophysically coupled method for joint inversion. We then analyze the resolution properties of a joint inversion problem where not only the thickness of the gas layer, the gas saturation and the sandstone porosity are unknown, but several rock physics parameters are as well. Results show that in certain cases, gas saturation and thickness can be independently resolved with a joint inversion. However, the sandstone porosity may be intercorrelated with the bulk and shear moduli of the sand. This result is one of many different outcomes and shall examine a variety of rock physics and reservoir models in our talk.