Pore-Space Reduction in Sandstones

In two deep wells in Wyoming three types of pore-space reduction occur. These are simple pore filling, solid flow, and solution and redeposition or removal of the dissolved material. Five sands, ranging in depth from 2,885 to 8,343 feet, and sections of randomly packed sand grains were studied. Sand-grain contacts, as they appear in the plane of a random thin section, are classified. The number of contacts per grain and types of contacts due to pressure increase with depth, and each type of contact has its individual trend with increasing depth. Development of tension cracks and crushing of fragile grains are other features due to pressure. Some cementation and replacement occur, but no depth relationship can be established.