Abstract:
© 2020 Saint Petersburg 2020 - Geosciences: Converting Knowledge into Resources. All rights reserved. Given the fact that huge volumes of world oil and gas reserves are contained in carbonate reservoirs, laboratory studies of the elastic properties of fluid-saturated carbonates are an area of research of great importance. In this paper, we consider the problem of the influence of pore fluid on the acoustic properties of carbonate rocks. The aim of the work was to identify changes in acoustic properties upon saturation. The P and S wave velocities were measured on 53 dry and saturated core samples. The velocities of 22 samples were measured during drying, at a saturation of 100, 75, 50, 25% and in a completely dry state. As a result, it was found that the S wave does not change upon saturation. P wave as expected increased at saturation. The effect of hysteresis of the P wave upon drying of the sample was also revealed. When saturated from 100 to 25%, the speed did not change, and when dried from 25 to 0%, the speed sharply decreased. This is due to the presence of “stiff” and “soft” pores in the rock samples. When drying, rounded stiff pores dry out first, so the speed does not change. Micropores and cracks then dry, and the speed decreases. This assumption was confirmed by lithological and microscopic studies on thin sections.
