碳酸盐岩强非均质储层相控反演方法研究

岩溶缝洞体是碳酸盐岩主要储层类型, 具有强非均质性特征, 量化预测难度大。常规地震反演方法虽然可实现储层的量化预测, 但满足不了岩溶缝洞体中多类型储层的量化及高精度研究需求。针对这一问题, 在相控约束反演技术思路的基础上, 提出了基于梯度结构张量属性约束的确定性相控反演方法。该方法可概述为3步: 首先, 基于梯度结构张量属性, 划分出反映碳酸盐岩缝洞体轮廓的储层相与非储层相; 其次, 以地震相为约束条件, 建立低频模型; 最后, 将低频模型应用于地震反演过程, 得到储层敏感属性, 进而实现碳酸盐岩强非均质储层的量化预测。模型试算结果和塔里木盆地M工区实际应用结果均表明, 该方法能有效识别岩溶缝洞体中多类型储层的分布范围, 与实钻结果及开发动态特征吻合, 为碳酸盐岩缝洞型油藏的整体量化研究奠定了基础。

Karst fractured-vuggy units are the main type of carbonate reservoirs and have strong heterogeneity; thus, it is difficult to accomplish quantitative prediction.Conventional seismic inversion methods are suitable for quantitative prediction of clastic reservoirs with weak heterogeneity.However, quantitative karst reservoir prediction with high precision is a much tougher problem.The idea of facies-controlled inversion is a plausible solution.By using discontinuity attributes, such as amplitude curvature, to identify carbonate reservoirs qualitatively, a low-frequency model is established to constrain the inversion process.The inversion results can further improve the resolution of the fracture-cavern reservoirs.On this basis, a deterministic facies-controlled inversion method based on gradient structure tensor is proposed.The method includes three steps.Firstly, based on the gradient structure tensor, reservoir facies and non-reservoir facies are divided to reflect the contour of the carbonate fractured-vuggy units.Secondly, a low-frequency model is established with seismic facies as the constraints.Finally, the low-frequency model is applied to the inversion process to obtain seismic attributes sensitive to reservoir properties and realize quantitative prediction of heterogeneous carbonate reservoirs.The results of model tests and a field application to Area M in the Tarim Basin show that the method is feasible for reservoir prediction with strong heterogeneity, as it pinpoints different types of carbonate reservoirs and predicts inter-cavity connectivity.Seismic prediction agrees with well drilling results and production performance.It lays the foundation for systematic quantitative study of carbonate reservoirs.