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岩石力学参数表征泥页岩的脆性,反映泥页岩在应力作用下发生破坏产生裂缝的能力.开展泥页岩的脆性评价研究,可为压裂设计提供技术支撑,是提高页岩产能的关键.鄂尔多斯盆地东南部下寺湾地区延长组长7段陆相泥页岩层系内大量发育粉砂质泥页岩条带,岩性非均质性强,对页岩气产量影响显著.针对这一地质实际,本文分页岩、粉砂质泥页岩两种岩性开展三轴压缩等力学实验,对力学弹性参数特征、应力-应变特征、岩石破裂模式及脆性进行了分析,认为其力学破坏具有明显的脆性断裂特征.通过不同岩性横波时差与纵波时差、密度等测井数据的最小二乘法拟合,构建横波波速模型,计算动态力学参数,并利用动静态力学参数间的关系,校正测井计算的力学参数,进而定量评价泥页岩层段脆性.通过误差分析,并与YY22井ECS测井解释的矿物组分脆性加以对比,认为本文计算的脆性剖面是可信的.综合实验分析和测井脆性评价结果,为确定下寺湾地区长7段内的高脆性段,优选压裂目的层,提供了重要的地质依据.
Rock mechanics parameters characterize the brittleness of shale and reflect the ability of shale to rupture and produce cracks under the stress.Study on the brittleness of shale can provide the technical support for fracturing design and is the key to improve shale productivity Large amount of silty shale bands are developed in the continental shale strata of the Member 7 of the Yanchang Formation in the Lower Tertiary Bay Area, southeast of the Ordos Basin, showing strong litho-heterogeneity and significant impact on shale gas production Geological reality, this paper shale, silt shale two kinds of lithology to carry out three-axis compression and other mechanical experiments, the mechanical characteristics of elastic parameters, stress-strain characteristics, rock failure mode and brittleness were analyzed, that the mechanical failure Has obvious brittle fracture characteristics.The shear wave velocity model is constructed by the least squares fitting of log data of different lithology time-lapse and longitudinal wave time difference and density, the dynamic mechanical parameters are calculated, and the relationship between dynamic and static mechanical parameters is used to correct Logging calculation of mechanical parameters, and quantitative evaluation of mud shale layer brittleness by error analysis, and YY22 well ECS logging interpretation of the brittleness of mineral composition to be compared, this article Brittle sectional count is credible. Comprehensive experimental results of analysis and evaluation logging brittle, frangible section to determine a taller inner segment 7, preferably fracturing object layer Xiasiwan area, provides an important geological basis.