Permeability anisotropy of Erin formation friable rocks under high effective pressures

Abstract

The reduction of carbon emissions is a global challenge. Carbon capture and sequestration has been established as a viable solution to the problem of rising carbon emissions. Consequently, mature and depleted fields, some of which are friable reservoirs, are increasingly being used to store CO₂. However, because it can be extremely challenging to obtain intact samples and prepare highly friable specimens for laboratory testing, very few studies have examined the permeability of highly friable rocks as compared to consolidated rocks. Therefore, there is a scarcity of data on the permeability of friable rocks. In this study, the permeability of the Erin Formation highly friable sandstone and thin-bed shale was measured under effective pressures, up to 130 MPa, in both perpendicular (k_v) and parallel (k_h) directions to bedding. The Erin Formation is a major reservoir from which oil has been produced in Southern Trinidad for the past century. The friable rocks exhibit low permeability, with ranges from 12.5 to 0.02 μD, and 0.2 μD to 2 nD for sandstone and thin-bed shale, respectively. The effective pressure has a substantial impact on permeability, causing the permeability to decrease as the effective pressure increases. The permeability is higher in the parallel bedding direction and the anisotropy (k_h/k_v) ranges from 17 to 421, which is greater in the sandstone. The results indicate that the flow of CO₂ during injection will be predominantly lateral along the beds with the thin-bed shale acting as a reliable seal to flow perpendicular to bedding.