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Effective Pressure for Elastic Wave Velocities of Sandstone
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 80th EAGE Conference and Exhibition 2018, Jun 2018, Volume 2018, p.1 - 5
Abstract
Studying the relation between the effective pressure and the elastic wave velocities of the rock is of great importance for the oil/gas exploration and production. In this work, we investigate the effective pressure for sandstone elastic wave velocities experimentally. The sandstone samples are subjected to both confining and pore pressures, which are changed at the same amplitude and hence keep the differential pressure constant. The P-and S- wave velocities are then measured using the ultrasonic pulse transmission method. The results show that the velocities and elastic moduli decrease with the pore pressure while keeping the differential pressure constant. This indicates that the effective pressure is different from the differential pressure, which is inconsistent with the previous research and hence a new expression for the effective pressure is needed. The analysis of the experimental results show that the effective pressure coefficient is pressure-dependent and increases when the effective pressure decreases. This provides the basis for finding the appropriate expression for the effective pressure in the future.