The effects of pore fluid distribution to the experimental velocity of partially saturated reservoir sandstones

The condition of high frequency at the experimental, the saturation dependence of the P-wave velocity in reservoir sandstone samples put up complex variation tendency when adopting conventional imbibitions saturation methods. Under the low confining pressure, P-wave velocity show non-linear increase with increasing water saturation; under the high confining pressure.P-wave velocity first decrease with increasing water saturation, and then increase with increasing water saturation after certain saturation, which are different from the theoretical results of effective fluid model commonly used in seismic exploration.The saturation dependence of elastic velocity based on effective fluid model and patchy saturation model was discussed elaborately, and some important conclusions have been draw. The effects of patchy saturation on compression wave velocity depend on frequency, which is also another kind of dispersion mechanism at much larger scales than any pore. After velocity calibration to eliminate the effects of Biot flow and squirt fluid, experimental velocity results of partially saturated rock samples are all in the region bounded by the predicted results of effective fluid model and patchy saturation model under low confining pressure.