With continued growth in world demand for oil and gas and declined production for conventional oil and gas, unconventional oil and gas with large resource potential has gradually become a new field of exploration. The tight oil becomes one of the highlights of global unconventional petroleum exploration and development.

Porosity and permeability of tight sandstone are very low. There is no natural production capacity or natural production capacity is very low in the general conditions. So, large-scale fracturing is needed to produce industrial oil and gas flow. However, experience has shown that the production of tight sandstones of different fracturing section and different perforation clusters is not the same due to lithology and stress factors caused by the heterogeneity even if the large scale fracturing is used. Therefore, it is important to investigate the anisotropic properties of tight sandstone.

To investigate the laws of tight sandstone wave velocity and anisotropy with confining pressure and elastic anisotropy characteristics under different saturated states, cores in different directions were drilled and their acoustic characteristics were measured under ultrasonic frequency in laboratory. Change laws of sample P and S wave velocity, stiffness coefficient, and anisotropy coefficient with increasing confining pressure were then analyzed. The experimental results indicate that P and S wave velocity, ratio of P wave to S wave and stiffness coefficient all raise with increasing confining pressure, but the change rates under different saturated status were entirely different. Ratio of P wave to S wave and anisotropy coefficients have inconspicuous change law under saturation state, this indicates that the existence of fluid is very important to rock physical properties. The experimental work is not only necessary to investigate tight sand elastic anisotropy characteristic under different fluid properties, but also contribute to identification of tight sandstone fluid and gas.

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