岩心力学实验刻度弹性参数的页岩脆性评价方法改进

Improvement of Shale Brittleness Evaluation Methods Based on Calibration of Elastic Parameters by Rock Core Mechanics Experiments

页岩储层的规模动用关键在于水力压裂造缝,复杂缝网形成的地质因素取决于天然裂缝、水平应力差及脆性,高脆性是压裂形成缝网的必要条件之一。针对现有弹性参数脆性指数评价方法中杨氏模量和泊松比权重系数占比不清的问题,在岩心三轴力学测试和全岩样品分析的基础上,提出基于应力-应变曲线的脆性评价指标,通过统计交会分析,明确杨氏模量和泊松比对岩石脆性敏感程度,并且根据脆性评价指标和杨氏模量及泊松比的相关系数,采用等比例方式进一步刻度杨氏模量和泊松比的权重系数,改进了现有的弹性参数脆性指数评价方法。东部盆地页岩层系应用实例表明,岩心力学实验刻度后的弹性参数脆性评价方法更加合理有效,能更好地反映页岩储层脆性分布特征。

The key to the scale utilization of shale reservoirs lies in the formation of fracturesby hydraulic fracturing.The geological factors that form complex fracture network depend on the natural fractures,horizontal stress difference and brittleness of shale reservoirs.High brittleness is one of the necessary conditions to form fracture network by fracturing.Aiming at the problem of unclear weight coefficients of Young’s modulus and Poisson’s ratio in existing methods for evaluating the brittleness index of elastic parameters,a brittleness evaluation index based on stress-strain curve is proposed based on triaxial mechanical testing of rock cores and analysis of whole rock samples.Through statistical intersection analysis,the sensitivity of Young’s modulus and Poisson’s ratio to rock brittleness was clarified.Based on the correlation coefficients between brittleness evaluation indicator and Young’s modulus and Poisson’s ratio,the weight coefficients of Young’s modulus and Poisson’s ratio were further determined using an equal proportion method,improving the existing evaluation methods for elastic parameter brittleness index.The application examples of shale formations in the eastern basin show that compared with existing evaluation methods,the elastic parameter brittleness evaluation method calibrated by core mechanics experiments is more reasonable and effective,and can better reflect the distribution characteristics of shale reservoir brittleness.