Tight Rock Permeability Measurement in Laboratory

Abstract

The laboratory measurement of tight rock permeability is important in several areas including hydrocarbon recovery from unconventional reservoirs, caprock integrity associated with CO 2 geological sequestration, and geological disposal of high-level nuclear wastes in tight rock formations. This chapter briefly reviews commonly used laboratory methods for tight rock permeability measurement, including the steady-state flow, pressure pulse-decay (PPD), and Gas Research Institute (GRI) methods, and then presents two newly developed laboratory methods. To overcome the challenge that plug-scale tight rock matrix permeability cannot be measured from fractured samples with currently available methods, we have developed a laboratory method to measure both fracture and matrix permeability from a fractured sample. The method is a generalization of the conventional PPD method and uses early-time data, dominated by fracture flow, to estimate fracture permeability and late-time data, dominated by matrix flow, to estimate matrix permeability. To deal with the inefficiency of conventional methods that are exclusively based on linear theories for fluid flow, we have also developed a laboratory method to directly measure the tight rock permeability as a function of pore pressure, with a single test run, from a non-fractured rock sample. It, unlike conventional methods, is based on a nonlinear theory of fluid flow and can increase measurement efficiency by at least multiple times. Both methods are validated with laboratory measurements.