基于叠前地震反演弹性参数的渝西W井区页岩储层水平地应力预测

Horizontal In-Situ Stress Prediction of Shale Reservoirs in the W Well Area of Western Chongqing Based on Elastic Parameters from Prestack Seismic Inversion

摘要: 针对页岩储层井间地应力难以连续表征的问题，以渝西W井区五峰组–龙一1亚段为研究对象，基于测井、岩心实验及叠前地震资料开展水平地应力预测。首先利用叠前同时反演获得纵、横波速度和密度等弹性参数，并计算杨氏模量和泊松比；结合岩心实验建立杨氏模量动静态转换关系，在此基础上利用弹性参数约束的水平地应力计算关系，预测最大、最小水平主应力及水平应力差异比(DHSR)，并采用DFIT及岩心声发射实验资料进行验证。结果表明，研究区最大水平主应力约为82~128 MPa，主体为95~118 MPa；最小水平主应力约为71~109 MPa，主体为80~100 MPa；DHSR约为0.08~0.25，主体为0.12~0.21，均表现出一定的空间非均质性。水平地应力空间变化与构造埋深并非简单对应，其非均质性受上覆载荷、岩石弹性性质、裂缝柔度和局部构造等条件共同影响。井点验证结果表明，预测结果与实测及实验资料具有较好的一致性，可实现水平地应力由井点向井间的连续表征，为页岩储层地质–工程评价提供参考。

Abstract: To address the difficulty of continuously characterizing interwell in-situ stress in shale reservoirs, the Wufeng Formation-Longyi-1 submember in the W well area of western Chongqing was selected as the study interval. Horizontal in-situ stress prediction was conducted using well-log, core experimental, and prestack seismic data. Prestack simultaneous inversion was first applied to obtain P-wave velocity, S-wave velocity, and density, from which Young’s modulus and Poisson’s ratio were calculated. A dynamic-to-static conversion relationship for Young’s modulus was established based on core experimental data. Subsequently, the maximum horizontal principal stress, minimum horizontal principal stress, and differential horizontal stress ratio (DHSR) were predicted using an elastic-parameter-constrained stress calculation method, and the results were validated using DFIT and core acoustic-emission data. The results show that the maximum horizontal principal stress ranges from approximately 82 to 128 MPa, mainly between 95 and 118 MPa, while the minimum horizontal principal stress ranges from approximately 71 to 109 MPa, mainly between 80 and 100 MPa. The DHSR ranges from approximately 0.08 to 0.25, mainly between 0.12 and 0.21, exhibiting evident spatial heterogeneity. The spatial variation in horizontal in-situ stress does not show a simple correspondence with structural burial depth, and its heterogeneity is jointly influenced by overburden loading, rock elastic properties, fracture compliance, and local structural conditions. Validation results show good agreement between the predicted and measured/experimental stress values. The proposed approach enables continuous characterization of horizontal in-situ stress from wells to interwell areas and provides a reference for geological-engineering evaluation of shale reservoirs.