Use of Compressional and Shear Wave Velocity for Overpressure detection

摘要

New results are presented that show overpressure can be detected from surface seismic, cross-well, sonic logs and measurements ahead of the drill bit. By analyzing experimental data we show that in many room-dry rocks, the Poisson's ratio (PR) decreases with decreasing differential pressure (confining minus pore pressure). This means that in gas-saturated rocks, PR decreases with increasing pore pressure. We confirm the generality of the observed effect by theoretically reproducing it via effective medium modeling. These results may prove useful in the extraction of "overpressure atributes" from seismic data.