鄂尔多斯盆地北部复杂碳酸盐岩横波速度预测研究

鄂尔多斯盆地北部D气田奥陶系马家沟组马五段发育了岩性和孔隙结构均复杂的碳酸盐岩,储层岩性为白云岩、灰岩中夹杂硬石膏、石英,部分层段黏土含量较高,采用工业界常用的经典碳酸盐岩岩石物理模型Xu-Payne模型不能有效求取该储层的横波速度。针对这一问题,将储层岩石等效为由白云石、方解石、黏土、石英、硬石膏及孔隙流体组成的混合物,将岩石中的孔隙简化等效为刚性孔隙与柔性裂缝,综合利用多孔隙类型微分Kuster-Toksz(简称DKT)岩石物理模型、Gassmann方程、Wood方程、VRH平均公式构建岩石物理模型,在纵波速度的约束下求出刚性孔隙与柔性裂缝的体积分数,进而求取横波速度。研究区实际测井资料应用上述方法求取的横波速度均方根误差、相关系数要明显优于用多矿物扩展的Xu-Payne模型及原始Xu-Payne模型的预测结果,验证了方法对于求取复杂岩性、复杂孔隙结构碳酸盐岩储层横波速度的适用性和有效性。

It developed carbonate reservoir with complex lithology and complex pore structure in the 5th Ma member of Majiagou formation,in D Gasfield of Ordos Basin.The lithology of reservoir developed in this area mainly includes dolomite and limestone mixed up with clay and anhydrite quartz,of which clay content is high.Xu-Payne model as a classical rock physics model for the carbonate reservoirs in the industry cannot effectively calculate the S-wave velocity in this area.In this article,the carbonate reservoir is equivalent to a mixture of dolomite,calcite,quartz,clay,anhydrite and pore fluid,simplifying the porosity of the reservoir as stiff pores and compliant fractures.Combined Gassmann equation,Wood equation and V-R-H average equation with multi-pore differential Kuster-Toksöz rock physics model,we establish a rock physics model for carbonate reservoir,on which the volume percentages of stiff pores and compliant fractures are inverted respectively using conventional logging data under the constraint of the P-wave velocity.Then,the volume percentages of stiff pores and compliant fractures are employed to calculate the S-wave velocity.When the method is applied to the actual logging data in the D Gasfield,the calculated root mean square error and correlation coefficients of the S-wave velocity from the new model have superiority over than the predicted results from Xu-Payne model.It proves that the above S-wave velocity prediction method is applicant and effective for the carbonate reservoir with complex lithology and complex pore structure.

国家科技重大专项“鄂北深层岩溶储层地震预测技术”(2017ZX05005-004-009)及中国石油化工股份有限公司科技部项目“鄂北奥陶系风化壳储层及含气性地震预测技术”(P16066)联合资助。