Modeling of elasticity effects of sandstone compaction using coated inclusions

Abstract

Compaction of siliciclastic sediments leads to an increase in their stiffness parameters and seismic velocities. Although mechanical compaction implies a reduction of porosity and closing of compliant pores, chemical compaction may alter the mineral properties, the cementing of grain contacts, and the pore volume. The ability of rock physics models to quantify such effects on seismic observables will aid hydrocarbon exploration. A framework was designed for modeling compaction effects by use of a so-called coated inclusion model that eliminates the need of using a hybrid approach through combining different theories. A basic feature of the model is that the inclusion is defined by a kernel representing the pore, which is surrounded by shells that may individually have different elastic properties from those of the pore-filling material and the background matrix. The modeling can be designed to explore seismic effects of various texture perturbations, including contact cementing and pore-filling processes. The numerical modelings seem to be consistent with the results obtained from other rock physics models. The model allows for the possibility of including small-scale heterogeneities within the rock texture and estimating frequency dispersion together with attenuation due to pore fluid flow. A basic weakness of the method is the relatively large number of parameters needed to describe a porous rock, which will always limit its practical usage. However, its basic physical foundation may provide a reference for understanding the qualitative and quantitative effects of various cementation scenarios on seismic parameters.