煤田地质与勘探2023，Vol.51Issue(11)：44-54,11.DOI:10.12363/issn.1001-1986.23.07.0397
层理特征对油页岩水力压裂裂缝扩展规律影响的数值模拟研究
Numerical simulations of the effects of bedding planes on hydraulic fracture propagation law in oil shale
摘要
Abstract
Hydraulic fracturing serves as a major technical means for the exploitation of oil shale reservoirs presently,and the hydraulic fracture morphology in oil shales is primarily affected by differences in the characteristics of bedding planes.However,current studies mostly focus on the influence of the developmental degree of bedding planes on frac-ture propagation,overlooking the effects of the bedding plane thickness itself on hydraulic fracture propagation.This study delves into the oil shale in the Xunyi area,Ordos Basin.Based on the theory of linear elastic fracture mechanics,this study developed a stress-damage-seepage model of hydraulic fracture propagation.Using the global numerical simu-lation method termed finite element method-cohesive zone method(FEM-CZM),this study analyzed the effects of the in-situ stress field and bedding planes'thickness and spacing on hydraulic fracture propagation,followed by comparing fractures'failure type and length and the area connected by bedding planes under different influencing factors.Key find-ings of this study are as follows:(1)The thickness of bedding planes affects their capacity to intercept hydraulic frac-tures.A large thickness will lead to a strong tendency of fracture propagation along laminae planes,thus inducing tensile failure.Accordingly,long fractures and a large area connected by bedding planes will be formed.(2)The bedding plane spacing affects the time for hydraulic fractures to reach bedding planes.In the case of a small spacing,hydraulic frac-tures will directly penetrate bedding planes.The spacing will increase the resistance to fracture propagation.A larger bedding plane spacing is associated with longer fractures and a larger area connected by bedding planes due to tensile failure.(3)the in-situ stress field determines the direction of the hydraulic fracture propagation.In the case of a large vertical in-situ stress difference,the vertical stress will compact bedding planes.As a result,hydraulic fractures are more prone to penetrate bedding planes.When the vertical in-situ stress difference is small,hydraulic fractures will bend and branch in the process of propagation on bedding planes,leading to increased fracture length and area connected by bed-ding planes.Based on these findings,it is recommended that hydraulic fracturing should be performed in areas with large thicknesses and spacings of bedding planes and a small vertical stress field,which are more favorable for the form-ation of efficient seepage and heat transfer channels.This study can provide guidance for the hydraulic fracturing con-struction for oil shale in the Xunyi area.关键词
油页岩/水力压裂/层理厚度/层理间距/地应力/数值模拟/裂缝扩展规律/鄂尔多斯盆地Key words
oil shale/hydraulic fracturing/bedding plane thickness/bedding plane spacing/in-situ stress/numerical sim-ulation/fracture propagation law/Ordos Basin分类
天文与地球科学引用本文复制引用
李彦伟,朱超凡,曾壹坚,水浩澈,范存翰,郭威..层理特征对油页岩水力压裂裂缝扩展规律影响的数值模拟研究[J].煤田地质与勘探,2023,51(11):44-54,11.基金项目
国家重点研发计划课题(2019YFA0705502) （2019YFA0705502）
吉林省中青年科技创新卓越团队项目(20220508135RC) （20220508135RC）
吉林省发展和改革委员会自主创新能力建设项目(2022C021) （2022C021）
