基于弹塑性井周的井筒-射孔地层破裂压力预测模型  

A prediction model of breakdown pressure of wellbore-perforation formation based on elastic-plastic around wellbore

作　　者：杨峰[1] 张敏[2] 孟宪波 丁然 陈磊 彭岩 YANG Feng;ZHANG Min;MENG Xianbo;DING Ran;CHEN Lei;PENG Yan(Petroleum Engineering Technology Research Institute of Sinopec Shengli Oilfield Company,Dongying 257001,China;College of Petroleum Engineering,China University of Petroleum-Beijing,Beijing 102249,China;West Oil and Gas Exploration Project Department,Sinopec Shengli Oilfield Company,Dongying 257001,China;Research Institute of Petroleum Exploration and Development,SINOPEC,Beijing 102249,China)

机构地区：[1]中国石化胜利油田分公司工程技术研究院,山东东营257001 [2]中国石油大学(北京)石油工程学院,北京102249 [3]中国石化胜利油田分公司西部油气勘探项目部,山东东营257001 [4]中国石化石油勘探开发研究院,北京102249

出　　处：《中国矿业》2024年第5期173-180,共8页China Mining Magazine

基　　金：国家自然科学基金项目“致密储层缝内变载荷驱动裂缝疲劳扩展机理研究”资助(编号:51974356);中国石油大学(北京)科研基金项目“砾岩油藏变载荷压裂井筒完整性失效力学机理研究”资助(编号:2462021YXZZ012)。

摘　　要：深部“高地应力、高温度、高地层压力”的赋存条件,使储层呈现脆性-延性-应变硬化的塑性特征。针对深部塑性储层的水力压裂改造,存在人工裂缝起裂、延伸压力高的挑战。本文通过开展实时高温高围压的储层岩石三轴压缩实验,明确了储层岩石的塑性破坏特征。建立了深部储层岩石的塑性硬化本构模型,推导了井周的弹塑性应力场分布。结合断裂力学理论,建立了考虑井周塑性区的射孔尖端应力强度因子计算模型,并提出相应的迭代求解方法。采用模型预测室内实验与新疆某油田实际条件下的水力压裂裂缝起裂压力,模型预测结果与实测结果对比表明,考虑弹塑性井周应力场的破裂压力预测值比实际压裂预测值高,储层塑性特征不利于水力裂缝的起裂。模型预测值与油田实测结果的误差为6.6%,验证了模型的可靠性。考虑弹塑性井周的破裂压力预测模型可保证压裂设计的安全性,为深部储层的压裂方案设计提供有效指导。The“high geostress,high temperature,and high formation pressure”conditions in the deep part of the reservoir make the reservoir show the plastic characteristics of brittle-ductile-strain hardening.Hydraulic fracturing for deep plastic reservoirs presents challenges of artificial fracture initiation and high extension pressures.In this paper,the plastic failure characteristics of reservoir rocks are clarified by conducting real-time triaxial compression experiments with high temperature and high confining pressure.Based on the experimental results,the corresponding plastic hardening constitutive model is proposed,and the distribution of elastic-plastic stress field around the wellbore is established.Based on the theory of fracture mechanics and considering the influence of plastic zone on the distribution of stress field around the wellbore,the calculation model of fracture toughness of perforation tip in the elastic-plastic stress field around the wellbore is derived,and the corresponding iterative solution method is proposed.The model is used to predict the fracture initiation pressure in laboratory experiments and actual conditions of an oilfield in Xinjiang.The comparison between the model prediction results and the measured results shows that the predicted value of fracture pressure considering the elastic-plastic stress field around the wellbore is higher than the actual fracturing pressure,and the plastic characteristics of the reservoir are not conducive to the initiation of hydraulic fractures.The error between the predicted value of the model and the measured result is 6.6%,which verifies the reliability of the model.The fracture pressure prediction model considering the elasticplastic around wellbore can ensure the safety of fracturing design and provide effective guidance for the design of deep reservoir fracturing schemes.

关 键 词：深部地层 破裂压力 弹塑性 井周应力场 井筒-射孔 

分 类 号：TD315[矿业工程—矿井建设] TE122.14[石油与天然气工程—油气勘探]