Rock physics templates for anisotropic and heterogeneous reservoir rocks considering mineralogy, texture and pore-filling fluid

Abstract

Anisotropic Rock Physics Templates (RPTs) are efficient tools to interpret well logs. In this work, micromechanical modeling is used to calculate the effective properties of heterogeneous and anisotropic rocks due to the presence of fluid-filled aligned fractures or other minerals, e.g. clay, quartz and calcite. When the spheroidal inclusions are aligned, the transversely isotropic symmetry is described by Hill’s 5 elastic moduli, which are obtained after solving a system of nonlinear algebraic equations. New anisotropic Rock Physics Templates are based on these elastic moduli, in which it is easy to identify the presence of fluids in a reservoir. It has been observed that effective properties depend strongly on the aspect ratio of inclusions, pore fluid, and mineralogy. These new numerical results are similar to with others already published when the aspect ratio is set to 1. For aspect ratios δ of 0.25,0.5, and 0.75, these ternary plots give new elements of interpretation and analysis of results obtained either in a rock physics laboratory or in the field station. For instance, lower aspect ratios δ=0.5 until values nearly to δ=1 consider thick interbedded formations or fluid-filled pore under compaction. The latter will lead to a better characterization of the heterogeneous and anisotropic reservoir rocks, which are linked to producing commercial hydrocarbon areas. Herein, a shale gas reservoir is consistently identified by the proposed anisotropic RPTs.