基于线弹性与损伤力学的砂砾岩裂缝扩展规律研究  

Study on the crack propagation law of conglomerate based on linear elasticity and damage mechanics

作　　者：刘洪涛[1] 王孟江[1] 肖诚诚 陈红旗 LIU Hongtao;WANG Mengjiang;XIAO Chengcheng;CHEN Hongqi(Research Institute of Petroleum Engineering Technology,Henan Oilfield Branch,SINOPEC,Nanyang 473000,Henan;Henan Pingdingshan Petroleum Branch of SINOPEC Sales Co.,Ltd.,Pingdingshan 467000,Henan)

机构地区：[1]中国石化河南油田分公司石油工程技术研究院,河南南阳473000 [2]中国石化销售股份有限公司河南平顶山石油分公司,河南平顶山467000

出　　处：《长江大学学报（自然科学版）》2024年第6期79-88,共10页Journal of Yangtze University(Natural Science Edition)

基　　金：低渗透油气田勘探开发国家工程实验室开放课题“深层煤岩气储层压裂缝网扩展数值模拟及改造方案设计优化研究”(2023-015)。

摘　　要：水力压裂法是提高砂砾岩油气藏开发效率的关键技术手段。采用线性弹性断裂力学与损伤力学原理,构建了一个描述裂缝在砂砾岩储层中动态扩展的理论模型,探究砂砾岩储层中水力裂缝的动态扩散过程。研究结果表明:在砂砾岩储层中水力裂缝以绕砾为主进行扩展,砾径变化不会对水力裂缝延伸方向产生较大影响;在水平井筒附近易形成复杂裂缝网络,扩展到远井区域后以简单缝为主。随着施工排量增加,近井起裂产生多裂缝的条数相应增加,在远井区域逐渐被优势裂缝扩展所取代,当排量达到10 m^(3)/min时最远沟通距离可达190 m。低黏度(1 mPa·s)压裂液易造成简单缝,中(10~30 mPa·s)、高黏度(50 mPa·s)压裂液易形成复杂缝,在远井区域形成优势扩展,高黏度压裂液形成裂缝遇砾石易分支,趋于形成垂直缝与水平缝相互连通的裂缝形态。随着水平应力差增加,裂缝复杂程度明显降低,且近井区域复杂缝网规模也在明显降低,目标区块应力差达到10 MPa时优势裂缝明显大幅度减少。该研究对于指导砾岩储层水力压裂的优化设计方案具有至关重要的作用。Hydraulic fracturing is a critical technique to enhance the development efficiency of conglomerate oil and gas reservoirs.Based on the principles of linear elastic fracture mechanics and damage mechanics,establishes a theoretical model to describe the dynamic propagation of fractures in conglomerate reservoirs and investigates the dynamic propagation process of hydraulic fractures in such formations.The results indicate that hydraulic fractures in conglomerate reservoirs primarily propagate around gravel particles,and changes in gravel size have minimal impact on the direction of hydraulic fracture extension.Complex fracture networks are likely to form near horizontal wellbores,transitioning to simpler fractures farther from the well.With the increase of construction displacement,the numbers of multiple fractures initiated near the wellbore increases,but gradually being replaced by dominant fractures in distal regions.When construction displacement reach 10 m^(3)/min,the maximum communication distance can reach 190 m.Low-viscosity(1 mPa·s)fracturing fluids tend to produce simple fractures,while medium(10~30 mPa·s)and high-viscosity(50 mPa·s)fracturing fluids are more likely to form complex fractures,forming advantages expansion in distal regions.High-viscosity fracturing fluids are easy to branch when encountering gravel,and form fracture patterns of interconnected vertical and horizontal fractures.With increase of horizontal stress difference,fracture complexity and the scale of the near-wellbore complex fracture network significantly decrease.When the horizontal stress difference reaches 10 MPa,dominant fractures are substantially reduced.This study provides essential guidance for optimizing hydraulic fracturing designs in conglomerate reservoirs.

关 键 词：砾岩储层 裂缝扩展 水力压裂 损伤力学 

分 类 号：TE34[石油与天然气工程—油气田开发工程]