The effects of temperature and confining pressure on the permeability of diatomite

The purpose of this experiment is to investigate the physical, mechanical, and chemical behavior of sedimentary rocks in the deep ground. We performed the permeability test of diatomite between room temperature and 140degC, under the effective confining pressure between 0.5MPa and 9.5MPa. The coefficient of permeability of diatomite increased with increasing temperature, but the intrinsic permeability was small between 80degC and 100degC (below 140degC). The intrinsic permeability of diatomite decreased with increasing the effective confining pressure from 0.5MPa to 9.5MPa. The effective porosity remarkably decreased with increasing the effective confining pressure from 3.5MPa to 4.5MPa by compression of diatom frustule, however the intrinsic permeability did not remarkably decrease on this pressure. The amount of volume reduction by silica dissolution from diatom frustule was 0.06% at 80degC and 0.12% at 140degC. (author)