Relationships Among Formation Resistivity Factor, Compressional Wave Velocity, and Porosity for Reservoirs Saturated with Multiphase Fluids

Abstract

The electric formation resistivity factor (F) and the seismic compressional wave velocity (v p) are powerful parameters in understanding the electric and elastic behavior of porous media and in identifying the type of fluid saturating the pore spaces. The formation resistivity factor is a function of various influences, including pore and grain properties; saturation, salinity, and viscosity of pore water; formation and pore-water resistivities; cation-exchange capacity; and clay content. The compressional wave velocity is a function of bulk (grain and fluid) density; type of saturant and degree of saturation; and various elastic moduli, including bulk (pore, fluid, and grain) compressibility. Both parameters (F and v p) are significantly affected by variations of porosity ( φ ), pressure, and temperature. The three parameters (F, v p, φ) were obtained from well log measurements for complex, heterogeneous, and consolidated shaly sandstone reservoirs, saturated with multiphase fluids, offshore of the eastern coast of Canada. Relationships among the three parameters, having coefficients of correlation ranging from 0.75 to 0.92, were obtained. Both F and v p are correlated inversely to φ and directly to each other.