An Investigation of the Permeability of Yorkshire Chalk under Differing Pore Water and Confining Pressure Conditions

The pores and pore throats of chalk form a very complicated network of channels through which fluid flow takes place. Due to the nonrigid character of the rock fabric, variations in pore water and confining pressures can cause significant changes to the intrinsic porosity and permeability of the rock. This paper describes the results of permeability tests at a series of high confining pressures and low pore water pressures performed on chalk from East Yorkshire, England. It has been found that permeability variations are more sensitive to changes in the pore water pressure than to changes in the confining pressure. Scanning electron microscope studies have indicated that pressure solution phenomena and grain deformation are responsible for permanent changes in porosity and permeability induced during the tests. The possibility of such changes occurring in production reservoirs is highly relevant to the choice of exploitation strategy.