天然气饱和度对岩石弹性参数影响的数值研究

Numerical Study of the Effect of Natural Gas Saturation on the Reservoir Rocks' Elastic Parameters

基于三维数字岩心,对岩石的弹性模量、纵横波速度、拉梅常数、泊松比等参数随不同含气饱和度变化规律进行数值研究。研究结果表明岩石的含气饱和度对横波速度影响不大,含气饱和度的增加将引起横波速度的缓慢增加。岩石的拉梅常数、泊松比、纵波速度、弹性模量和纵横波速度比随含气饱和度的增加而减小,当含气饱和度较低时,它们随含气饱和度增加急剧降低。将各弹性参数随含气饱和度的变化率进行比较,发现对天然气饱和度变化最敏感的参数是拉梅常数,其次是泊松比、体积模量和纵横波速度比等。该研究有助于选取对天然气饱和度变化敏感的参数计算储层的含气饱和度,从而提高计算精度。

The variation law of the effect of natural gas saturation on the reservoir rocks＇ elastic parameters, such as elastic moduli, P-wave and S-wave velocities, Lain6 constant, Poisson＇s ra-tio, is studied based on 3D digital cores. The results show that gas saturation of reservoir rocks has little influence on S-wave velocity and the S-wave velocity increases slowly with the increase of gas saturation. The elastic parameters, such as Lam6 constant, Poisson＇s ratio, P-wave veloc-ity, the ratio of P-wave velocity to S-wave velocity, decrease as the gas saturation increases. Mo-reover, they are changed sharply when the sandstone contains very small amount of gas. After comparing the change ratios of the elastic parameters with the variation of gas saturation, it is found the Lam6 constant is most sensitive to the variation of gas saturation, followed by Poisson＇s ratio, bulk modulus and the ratio of P-wave velocity to S-wave velocity. Through this study, the parameter which is sensitive to change of gas saturation can be used to calculate gas saturation of reservoir rocks in order to improve the calculation accuracy.