流体饱和度对裂缝—孔隙岩石频变纵波速度及其各向异性的影响  

Effect of fluid saturation on frequency-dependent P-wave velocity and anisotropy of fractured porous rock

作　　者：孔丽云 马彦彦 周惠 刘海浩 KONG LiYun;MA YanYan;ZHOU Hui;LIU HaiHao(Oil and Gas Survey,China Geological Survey,Beijing 100083,China)

机构地区：[1]中国地质调查局油气资源调查中心,北京100083

出　　处：《地球物理学报》2023年第9期3882-3892,共11页Chinese Journal of Geophysics

基　　金：中国地质调查局项目(DD20221653,DD20230325)和中国地质调查局油气资源调查中心(油科创(2023)-YC05号)资助。

摘　　要：流体饱和度会改变裂缝性储层的纵波速度,从而影响地层速度的频散特性及各向异性程度,导致储层地震响应特征复杂,储层预测多解性强,流体识别难度大.本文根据多相流体饱和裂缝性储层的特点,借助于Norris和KG模型,建立部分饱和裂缝-孔隙等效介质模型,给出频变地震波速度随流体饱和度变化的精确关系式.数值模拟结果表明,当气、水两相共存时,随着含水饱和度的增加,高频段纵波相速度逐渐增大,各向异性程度逐渐减小;低频段纵波相速度逐渐减小,各向异性程度不变;相速度频散及其各向异性程度逐渐增强.组合已有的孔隙弹性理论模型,对实验室人工裂缝-孔隙砂岩岩样的纵波速度进行拟合,计算得到的曲线与实验室测量散点值吻合度较高,表明组合模型在给定参数下的有效性.该研究能够为多相流体饱和裂缝性储层的地震响应特征分析奠定扎实的理论基础,为提高储层预测的确定性和流体识别的准确性提供可靠的理论依据.Fluid saturation will change the P-wave velocity of fractured reservoirs,thereby affecting the dispersion characteristics and velocity anisotropy,increasing the complexity of seismic response,multiple solution of reservoir prediction and difficulty of fluid identification.In this paper,according to the characteristics of fractured reservoirs saturated with multi-phase fluids,a partially saturated fractured porous equivalent medium model is established based on Norris and KG models.The exact relationship of P-wave velocity and fluid saturation is further derived.Numerical simulation results show that when gas and water coexist,with the increase of water saturation,P-wave phase velocities gradually increase,with decreasing degree of anisotropy at high frequencies,while P-wave phase velocity gives opposite trend with unchanged degree of anisotropy at low frequencies.The velocity dispersion and its degree of anisotropy gradually increase.Combining the existing poroelasticity theoretical models,we fit the P-wave velocity of a laboratory artificial fracture-porous sandstone sample.The calculated curvea match the measured scatter values reasonably,indicating that the combined model set is effectiveness under the given parameters.These results can lay a solid theoretical foundation for further analysis of seismic response characteristics of multiphase fluid-saturated fractured reservoirs,and provide a reliable theoretical basis for improving the certainty of reservoir prediction and the accuracy of fluid identification.

关 键 词：裂缝-孔隙岩石 流体饱和度 频变纵波速度 频散 各向异性 

分 类 号：P631[天文地球—地质矿产勘探]