1. n. [Reservoir Characterization]

Regression techniques that find relationships between two or more variables that have a complex (nonlinear) relationship. Porosity and permeability relationships are often of this form in rocks that have multiple porosity types (primary, intergranular, fracture or vugular porosity, for example) or multiple cement types and other variables that affect permeability.

See: fracture porosity,  porosity,  primary porosity,  vugular porosity