基于Q弹性阻抗流体因子反演研究

Fluid factor inversion based on Q elastic impedance

1.中石化石油物探技术研究院有限公司,江苏南京 211103;
2.中国石油化工股份有限公司西北油田分公司,新疆乌鲁木齐 830011;
3.中国石油化工股份有限公司胜利油田分公司物探研究院,山东东营 257000

1. SINOPEC Geophysical Research Institute Co.,Ltd.,Nanjing 211103,China;
2. SINOPEC Northwest Oilfield Branch,Urumqi 830011,China;
3. Geophysical Research Institute of Shengli Oilfield Company,SINOPEC,Dongying 257000,China

流体因子反演的难题在于地层介质的正问题从弹性过渡到非弹性介质后如何建立非弹性介质的反射系数表达式,从而更精确地描述传播介质。针对地震波在非弹性介质中的衰减问题,建立了基于Q弹性流体因子理论,结合衰减系数对弹性流体因子项进行扰动获得Q弹性流体因子,在相似介质和弱衰减假设条件下推导了Q弹性流体因子在介质分界面上的散射方程,该表达式与复数条件下的纵、横波速度项及密度项有较高的相关度;进一步通过Q弹性流体因子推导了与纵横波速度的关系,获得了近似条件下Q弹性流体因子纵波反射系数表达式,并分析了该表达式与完全弹性介质反射系数表达式的联系,该方法消除了反演剖面中存在的虚假亮点干扰,从而对衰减弹性介质假设下的储层流体响应进行了更准确的描述。在胜利油田某实际工区的应用结果表明:对流体和围岩进行了区分,获得了相比于常规流体因子反演结果更准确的储层流体响应特征,该流体检测方法在一定程度上降低了流体检测的多解性,消除了仅考虑振幅影响的识别假象。

The problem of fluid factor inversion lies in the forward modeling using the reflectivities of inelastic media instead of elastic media for an accurate description of propagation.For seismic wave attenuation in inelastic media,a Q-based elastic fluid factor is obtained by disturbing the elastic fluid factor term with attenuation coefficient.The scattering equation of the Q elastic fluid factor at the interface is derived under the assumptions of similar media and weak attenuation.The expression highly correlates with the P-velocity,S-velocity,and density terms in the context of complex number.The relationships between Q elastic fluid factor and P- and S-velocities are derived to obtain the equation of P-reflectivity of Q elastic fluid factor under above assumptions,and the relation between this equation and the reflectivity equation of perfectly elastic media is analyzed.Our method eliminates false bright spots on inversion sections,and thus it is possible to obtain accurate fluid responses under the assumption of attenuation elastic media.Field data application to Shengli oilfield shows more distinguishable fluid responses from surrounding rock responses compared with the routine method of fluid factor inversion.Our method mitigates the uncertainties of fluid detection to some extent and eliminates the artifacts generated by single-factor detection merely using amplitude.

国家自然科学基金项目(42174135,42074143)和国家重点研发计划变革性技术关键科学问题重点专项(2018YFA0702503)共同资助。

10.12431/issn.1000-1441.2024.63.04.011