We have developed a probabilistic method to invert reflectivity quotients for fluid modulus given imperfect data and incomplete information. The method does not require perfect amplitude calibration and outputs a fluid modulus probability density function. Numerical tests indicate that the results are most accurate when shear-wave reflectivities are utilized and when rock parameters are well known. However, even with imperfect measurements and knowledge, the inversion may yield distributions that are sufficiently narrow to distinguish gas from brine saturated porous sandstones, and provides a means to synthesize all known information and summarize this knowledge in terms of implied fluid modulus.
The fluid modulus inversion problem seeks to deduce information concerning the identity of a fluid saturating a particular rock by comparing seismic response of the rock to that obtained when the rock is saturated with some other fluid.
