Swelling shales and compacting cakes

摘要

Swelling clays are important to the petroleum industry because of their use in drilling fluids and because of their presence in shales through which oil wells are drilled. Models for compaction of clay filtercakes are discussed; these models incorporate chemical effects both in the equilibrium stress-strain relation and in the transport relations for water and ions. Analyses of shale swelling similarly require models both for equilibrium and for transport. A theory based upon Biot poroelas-ticity is applied to a wellbore geometry, and laboratory experiments are presented. Transport through a clay membrane is analysed in terms of linear relations for the fluxes of water and ions as functions of the jump in chemical potentials across the membrane, and the analysis is used to interpret experiments.