垂直裂隙P波响应特征分析

Analysis on P-wave seismic response of vertical fractures

应用反射P波数据预测裂缝发育带,进行流体识别是当前地震勘探的重点和难点。利用各向异性弹性波方程交错网格高阶有限差分数值模拟方法,开展了不同密度和不同充填物的垂直裂隙介质的波场响应特征研究。对不同模型反射P波的振幅和速度随方位角和炮检距的变化特征进行了定量的分析和总结。研究结果表明,当地层中含有单组垂直的平行裂隙时,反射P波振幅对垂直裂隙中充填物的敏感性大于速度对裂隙中充填物的敏感性,随着裂隙密度的增加,P波各向异性程度也相应增强,裂隙中含气时,各向异性程度较含饱和水时强。在一定程度上,为利用P波属性进行垂直裂隙油气藏的检测提供了理论依据。

To predict fractured zones and identify fluid in reservoir by using reflected P-wave information are important for current seismic exploration,but it is difficult.Based on anisotropic elastic wave equation staggering grid high-order finite-difference numerical simulation, the wave field response characteristics of vertical fracture medium with different densities and infillings were studied.The variable characteristics of P-wave amplitude and velocity via azimuth and offset inversed by different models were quantitatively analyzed and summarized.The results show when formations contains a single vertical parallel fracture system,the amplitude of reflected P-wave is more sensitive than velocity for different infillings of vertical fractures;the anisotropy increases as fracture density increasing; the anisotropy of gas-bearing fracture is stronger than the fracture saturated with fluid.To some degree,the results provide theoretical items for the detection of reservoir with vertical fractures by using P-wave attributes.