Method and device for the study of the shear waves indirect

摘要

A method and apparatus for estimating shear wave velocities where such velocities are difficult or impossible to measure because the shear energy transmission is attenuated or its velocity is equal to or less than direct mud velocity or because the shear wave may not propagate at all under certain conditions. The method and apparatus relate to an indirect technique for determining shear modulus by measuring the phase velocity of the Stoneley wave excitation and using it to estimate the shear modulus and the shear velocity. Using at least two receivers, a window is placed over the Stoneley arrival of the wave detected at each receiver and the Fourier transform of each wave is taken. The difference in phase of the Stoneley wave arrivals is determined. The relative shear modulus involving the Lame constants is estimated by a procedure which includes matching two points on Stoneley wave dispersion curves. From the relative shear modulus, the ratio of formation density to the density of mud, and the compressional velocity of the borehole mud is estimated the shear velocity.