SHALE ALTERATION BY WATER ADSORPTION

Abstract

In tests on samples of 50 shales from formations ranging in depth from 300 to 16,000 ft, it was found that the degree of alteration resulting from water adsorption depends on the types and amounts of clays contained in the shales. Unless hydration was controlled, unconfined samples expanded so much that shale density measurements could not be used for correlating or predicting abnormal pressure zones. For the shales tested, the amount of water absorbed at ambient conditions was an indication of the amount of clay in the shale and of the magnitude of stresses that might be developed by the shale in situ.