基于快速反射率法的AVA反演技术在致密砂岩薄储层勘探中的应用

Application of AVA inversion technique based on rapid reflectivity method in thin tight gas reservoir exploration

1.页岩油气富集机理与有效开发国家重点实验室,北京100083;
2.中国石化弹性波理论与探测技术重点实验室,北京100083;
3.中国石油化工股份有限公司石油勘探开发研究院,北京102206

1. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development,Beijing 100083,China;
2. Sinopec Key Laboratory of Seismic Elastic Wave Technology,Beijing 100083,China;
3. Sinopec Exploration and Production Research Institute,Beijing 102206,China

致密砂岩储层成层性明显且具有储层厚度薄的特点。传统的地震数据处理技术不能有效地压制地层内部的多次波,也不能准确地补偿传输损耗,使得基于Zoeppritz方程或其近似值的AVA反演理论不适用于致密砂岩储层。提出了一种以快速反射率算法为驱动核心的叠前AVA反演方法,快速反射率法可以计算全波响应,包括反射、透射、转换波和内部多次波,适用于致密砂岩储层,并利用薄层模型对方法进行了验证分析。目标函数的构建基于Gauss-Newton法,并推导出雅可比矩阵的解析解,提高了反演的准确度和收敛速度。将该方法分别应用于不含噪声和含噪声的薄互层模型数据,测试结果表明,基于快速反射率法的反演结果更加准确且具有一定的抗噪能力。四川崇州工区的实际数据应用结果表明,基于快速反射率法的正演模拟结果与实际地震数据更加接近,此外基于快速反射率法的反演结果更接近于测井曲线,更准确地反映地层变化的趋势,能更好地识别致密砂岩储层。

Tight gas reservoirs are characterized by apparent stratification and thin reservoirs,in which internal multiples are difficult to suppress and accurate compensation of transmission loss is difficult.Therefore,AVA inversion methods based on the Zoeppritz equations or their approximations are not applicable to thin interbeds.In this study,we propose a prestack AVA inversion method based on the rapid reflectivity method.The rapid reflectivity method can compute full-wave responses,including reflections,transmissions,mode conversions,and internal multiples,and it is beneficial for the seismic inversion of tight gas reservoirs.Another advantage of the rapid reflectivity method is that the partial derivatives of the reflection coefficient with respect to the elastic parameters can be expressed as analytical solutions.Based on the theories of the rapid reflectivity method,we established an objective function using the Gauss-Newton approach.To estimate the elastic parameters (P- and S-wave velocities and density),the objective function was established by minimizing the difference between the simulated and observed data in the angle domain.Eventually,we implemented the rapid reflectivity method-based inversion on the thin interbed model and field data and then compared it with the inversion method based on the exact Zoeppritz equation.The forward simulation results based on the rapid reflectivity method were closer to the field seismic data.The inversion results demonstrate that the rapid reflectivity method-based inversion can accurately reflect the trend of reservoir change and identify tight gas reservoirs.

中国石化科技部项目(P21050-3)资助。

10.3969/j.issn.1000-1441.2023.01.011