鄂尔多斯盆地南部长7页岩油储层地质力学特征及可压裂性评价

    • 摘要: 鄂尔多斯盆地是我国重要的非常规油气产区,其内延长组长7储层页岩油富集,勘探开发潜力巨大。储层地质力学评价是指导和实现鄂尔多斯盆地页岩油效益开发的关键。查明长7页岩油储层地质力学特征,并建立定量预测模型,是支撑储层可压裂性评价、甜点区段优选的重要依据。本研究采集盆地南部典型井延长组长7储层岩芯样品,通过实验测试获取弹性模量、泊松比、现今地应力等地质力学参数,以其为约束,借助BP神经网络构建基于测井数据的地质力学参数预测模型,分析长7页岩油储层地质力学特征,并评价其可压裂性。研究结果表明:1)基于BP神经网络的储层地质力学参数预测模型精度高,预测结果与实测值误差小;2)长7页岩油储层关键地质力学参数具非均质性,弹性模量介于16.26~59.12 GPa,断裂韧性介于0.2~1.2 MPa·m0.5,水平最大主应力和水平最小主应力分别介于20~43 MPa和12~38 MPa;3)构建基于储层地质力学参数的长7页岩油储层可压裂性评价指标F,据其划分储层为4等级:I类储层F>2.00,II类储层2.00>F>1.50,III类储层1.50>F>0.10,IV类储层F<1.00。研究结果可为储层压裂优化设计提供科学指导。

       

      Abstract: The Ordos Basin is an important unconventional oil and gas production area in China. The Yanchang Formation Chang 7 reservoir is rich in shale oil and has great potential for exploration and development. Reservoir geomechanics evaluation is critical for guiding and realizing the efficient development of shale oil in Ordos Basin. Identifying the geomechanical characteristics of Chang 7 shale oil reservoir and establishing a quantitative prediction model are important bases for supporting reservoir fracturability evaluation and sweet spot interval optimization. In this study, typical Chang 7 reservoir core samples in southern Ordos Basin were collected, and geomechanical parameters such as elastic modulus, Poisson's ratio, present-day in-situ stresses were experimentally determined. Further, a geomechanical parameter prediction model based on logging data was constructed with the BP neural network to achieve quantitative evaluation of geomechanical parameters and fracturability in the Yanchang Formation Chang 7 shale oil reservoir. The results show that: 1) the reservoir geomechanical parameter prediction model based on BP neural network has high accuracy, and the error between prediction results and measured values ​​is small; 2) the key geomechanical parameters of Chang 7 shale oil reservoir are heterogeneous, elastic modulus is between 16.26 and 59.12 GPa, fracture toughness is between 0.2~1.2 MPa·m0.5, the horizontal maximum principal stress and the horizontal minimum principal stress are between 20 and 43 MPa, 12 and 38 MPa, respectively; 3) the Chang 7 shale oil fracturability evaluation index F based on reservoir geomechanical parameters is constructed, and the reservoir grades are divided. According to the classification, the reservoirs are divided into four levels: Class I reservoirs F>2.00, Class II reservoirs 2.00>F>1.50, Class III reservoirs 1.50>F>0.10, and Class IV reservoirs F<1.00. The research results can provide scientific guidance for reservoir fracturing optimization design.

       

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