IMPORTANCE OF CLAY IN PETROLEUM GEOLOGY
IMPORTANCE OF CLAY IN PETROLEUM GEOLOGY Clay is the common name for a number of fine-grained, earthy materials that become plastic when wet. Chemically, clays are hydrous aluminums silicates, usually containing minor amounts of impurities such as potassium, sodium, calcium, magnesium, or iron. One of the commonest processes of clay formation is the chemical decomposition of feldspar. Clay consists of sheets of interconnected silicates combined with a second sheet-like grouping of metallic atoms, oxygen, and hydroxyl, forming a two-layer mineral such as kaolinite. Sometimes the latter sheet like structure is found sandwiched between two silica sheets, forming a three-layer mineral such as vermiculite. In the lithification process, compacted clay layers can be transformed into shale . Under the intense heat and pressure that may develop in the layers, the shale can be metamorphosed into slate . Properties of clay minerals include plasticity, shrinkage under firi...