Shale gouge ratio (typically abbreviated to SGR) is a mathematical algorithm that aims to predict the fault rock types for simple fault zones developed in sedimentary sequences dominated by sandstones and shales. The parameter is widely used in the oil and gas exploration and production industries to enable quantitative predictions to be made regarding the hydrodynamic behavior of faults. At any point on a fault surface, the shale gouge ratio is equal to the net shale/clay content of the rocks that have slipped past that point.