鄂尔多斯盆地大牛地气田致密砂岩储层三维岩石力学参数场研究

作为中国石化重要的天然气勘探开发基地之一，鄂尔多斯盆地大牛地气田上古生界致密砂岩气藏目前水平井压裂开采效果不理想。针对该气田上古生界致密砂岩储层岩石力学参数研究较为薄弱的现状，在对目的层岩心力学参数单轴/三轴压缩试验测试和纵横声波速度测试的基础上，首先建立了静态、动态弹性参数转换关系和纵横波速关系；在此基础上结合前人成果构建了岩石力学参数单井计算模型；并进一步运用测井资料和三维地震层速度资料确定了目的层力学参数场特征。结果表明，该区上古生界致密砂岩储层内聚力在2～10MPa之间，内摩擦角在30°～42°之间，抗张强度多数集中在5～15MPa之间，抗压强度多数集中在150～250MPa之间。太2段-盒1段弹性模量大部分在15～40GPa之间，泊松比在0.22～0.27之间，横向上每一层岩石弹性参数都存在明显的非均一性，垂向上随深度增加岩石力学参数呈变大趋势。该研究成果一方面可为该区地应力场模拟、气田钻完井设计及目的层压裂改造施工提供基础力学参数，同时研究中确定的动静态岩石力学参数转换、纵横波速等定量关系可为邻近地区相关研究提供参考或借鉴。

Research on Three-dimensional Mechanical Parameters′ Distributionof the Tight Sandstone Reservoirs in Daniudi Gasfield

Based on mechanical parameters testing by uniaxial/triaxial compression experiment and compressinal & shear acoustic velocities testing,the relationship between the static and dynamic elastic parameters of the tight sandstone reservoirs of Daniudi Gasfield in the Ordos Basin was established,then a single-well calculation model of mechanical parameters was constructed referring to predecessors′ achievements,further the characteristics of mechanical parameters field were investigated with log data and three-dimensional seismic interval velocity data.The results show that the cohesion of the Upper Paleozoic tight sandstone reservoirs ranges from 2MPa to 10MPa,the angle of internal friction being between 30° and 42°,the tensile strength mostly being between 5MPa and 15MPa,and the compressive strength mostly being between 150MPa and 250MPa.The modulus of elasticity of C₂t₂-P₁x₁ sandstone reservoirs is mostly between 15GPa and 40GPa,and their Poisson′s ratio is between 0.22 and 0.27.The rock elastic parameters show obvious inhomogeneities horizontally and their values increase with depth vertically.The research results can provide basic mechanical parameters for stress field simulation,gas drilling & completion design and target-layers′ fracturing,additionally the quantitative relationship between the static and dynamic mechanical parameters and that between the shear and longitudinal wave velocity might supply a reference for similar study in surrounding areas.