Method of determining shear wave travel time in subsurface formations

摘要

Methods for estimating shear wave travel time in formations of mixed lithology employing the compressional wave travel time in conjunction with other logging derived information. A shear/compressional wave travel time ratio is established for a sand formation as a function of the porosity of the formation. A shear/compressional wave travel time ratio is established for a shale formation as a function of bulk shale density as derived from the bulk density of the formation. A shale factor is used to compensate the two ratios to the mixed lithology of the measured formation providing a shear/compressional wave travel time ratio for the measured formation. Shear wave travel time is determined using the formation travel time ratio and a compressional wave travel time measurement.