Fines migration and compaction in diatomaceous rocks

The effect of confining pressure on permeability was investigated by repeated loading and unloading of outcrop cores at different intermediate pressures and temperatures. With increasing net effective stress, significant permeability degradation was observed with a noticeable acceleration at about 600 psia. Mercury porosimetry of damaged material indicates that changes may be due to pore collapse. Almost no permeability recovery was detected when the core was unloaded. Significant creep was observed with significant permeability reduction resulting from a constant applied confining pressure. Permeability reduction at a slightly smaller effective stress was observed for the high temperature cases but no significant material differences in the primary compaction curves were detected between 25 °C and 100 °C. Limited rebound suggests that the stress history of diatomites may be a significant factor in determining the degree of acceptable depletion in the field development planning for thermal operations.