Small Scale Permeability Measurements at Evelated Pressures: Analysis and Correction of Experimental Error using Micro Xray-CT

Abstract

The experimental measurement of permeability on small samples with rough surfaces under high confining pressure is subject to signific ant errors caused by boundary effects. These include the performance of various sleeve materials as well as core damage through coring and uneven compaction across the sample. Thus, under these conditions it is difficult to accurately measure permeability as function of applied stresses/strains. In this work we use samples of Bentheimer and Castlegate sandstone as well as Mt Gambier limestone and a sucrosic dolomite. Plugs with diameters between 5mm and 7mm are cut and placed into a purpose-built tri-axial cell on a micro-CT rotation stage. The plugs are surrounded radially by a sleeve separating confining fluid from the samples and axially by fluid distribution heads made of steel which also supply the axial load. We consider hydrostatic confinement and acquire images as well as measure permeability first at low confining pressure, then at high confining pressure, and again at low confining pressure (unloaded). Show more