Evaluation of a permeability-porosity relationship in a low permeability creeping material using a single transient test

TL;DR

This paper introduces a method to evaluate the permeability-porosity relationship in low-permeability materials using a single transient test, accounting for elastic and non-elastic deformations, and applies it to cement paste.

Contribution

It presents a novel analysis technique that incorporates creep effects to determine permeability-porosity relationships from a single test in low-permeability materials.

Findings

Permeability-porosity relationship calibrated with a power law exponent of 11.

Method effectively accounts for creep during the test.

Permeability evolution is mostly independent of stress and creep strains.

Abstract

A method is presented for the evaluation of the permeability-porosity relationship in a low-permeability porous material using the results of a single transient test. This method accounts for both elastic and non-elastic deformations of the sample during the test and is applied to a hardened class G oil well cement paste. An initial hydrostatic undrained loading is applied to the sample. The generated excess pore pressure is then released at one end of the sample while monitoring the pore pressure at the other end and the radial strain in the middle of the sample during the dissipation of the pore pressure. These measurements are back analysed to evaluate the permeability and its evolution with porosity change. The effect of creep of the sample during the test on the measured pore pressure and volume change is taken into account in the analysis. This approach permits to calibrate a power law permeability-porosity relationship for the tested hardened cement paste. The porosity sensitivity exponent of the power-law is evaluated equal to 11 and is shown to be mostly independent of the stress level and of the creep strains.