Estimation of reservoir porosity and saturations using multiple sources of geophysical data

This paper is aimed at developing a technique for estimation of porosity and saturations of up to two phases by using several sources of geophysical data. The method is based on the use of four sources of geophysical information, namely, inversion of normal incidence reflection seismology data, high resolution velocity analysis, well-log methods, and ultra-sonic well-log estimates of P and S velocities in boreholes. It is assumed that the relationship between porosity and measured geophysical parameters are described by a model belonging to a predefined set of models. The model-related functions of measured geophysical parameters are approximated by a combination of predefined porosity-saturation functions. The results of these approximations are then used for the prediction of porosity when several measured geophysical parameters are available. In the case of two-phase media, a relative volume of each phase may be derived using acoustic impedance11Acoustic impedance is the product of rock density and acoustic velocity. timates of velocities or densities based on the use of a system of balance equations. For a three-phase medium, estimates of P and S velocities (or acoustic impedances) and densities may be used jointly to estimate relative volumes of all three components.