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破碎岩石内水力裂缝扩展数值模拟研究

Numerical Simulation of Hydraulic Fracture Propagation in Broken Rock
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摘要 爆炸-水力复合压裂是深层页岩油气开采的新型方法,即通过水力压裂的方法在爆炸后井筒周围形成的破碎岩石中使水力裂缝迅速在破碎岩石内竞争扩展,形成复杂缝网,对深层页岩油气的开采具有重大意义。在最大能量释放率理论基础上,首先推导了破碎岩石内裂缝扩展能量释放率计算式,然后结合内聚力单元和随机泰森多边形,建立了破碎岩石内水力扩展模型,分析了应力差、破碎单元数量、断裂韧性比、施工排量和井周初始裂缝数量对水力裂缝扩展的影响规律。结果表明:应力差从1 MPa增大至9 MPa时,裂缝总长度和平均裂缝延伸速率分别降低了37.79%和33.11%;断裂韧性比的增大会极大地提高破裂压力从而减小应力差的干扰,且断裂韧性比从0.1增大至0.5时,总缝长提高了38.46%,同时也导致平均裂缝延伸速率降低了32.10%;排量和井周初始裂缝条数均与裂缝总长度和平均裂缝延伸速率均呈正相关,但破碎单元数几乎不会改变裂缝延伸速率,并与裂缝总长度呈正相关。 Explosion-hydraulic composite fracturing is a new method for deep shale oil and gas exploitation,that is,the hydraulic fracture is rapidly expanded in the broken rock formed around the wellbore after the explosion by hydraulic fracturing,forming a complex fracture network,which is of great significance to the exploitation of deep shale oil and gas.Based on the theory of maximum energy release rate,the calculation formula of energy release rate of fracture propagation in broken rock was derived firstly.Then,combined with cohesive element and random Thiessen polygon,the hydraulic propagation model in broken rock was established.The influence of stress difference,number of broken elements,fracture toughness ratio,construction displacement and initial fracture number on hydraulic fracture propagation was analyzed.The results show that when the stress difference increases from 1 MPa to 9 MPa,the total crack length and average crack extension rate decrease by 37.79% and 33.11%,respectively.The increase of fracture toughness ratio will greatly improve the fracture pressure and reduce the interference of stress difference.When the fracture toughness ratio increases from 0.1 to 0.5,the total fracture length increases by 38.46%,and the average fracture elongation rate decreases by 32.10%.The displacement and the number of initial fractures around the well are positively correlated with the total fracture length and the average fracture extension rate,but the number of fracture units hardly changes the fracture extension rate and is positively correlated with the total fracture length.
作者 邱思杨 李沁 陈文玲 石明星 张建伟 雷雲 QIU Si-yang;LI Qin;CHEN Wen-ling;SHI Ming-xing;ZHANG Jian-wei;LEI Yun(College of Energy,Chengdu University of Technology,Chengdu 610059,China)
出处 《科学技术与工程》 北大核心 2023年第24期10281-10297,共17页 Science Technology and Engineering
基金 国家自然科学基金(U20A20265)。
关键词 破碎岩石 水力裂缝 断裂韧性 裂缝复杂程度 破裂压力 broken rock hydraulic fracture fracture toughness fracture complexity breakdown pressure
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