摘要
煤岩储层内发育大量的割理、层理、天然裂缝等弱固结面,孔隙结构复杂,导致水力压裂期间裂缝扩展形态难以预测。明确煤层弱固结面与水力裂缝相交扩展规律,有利于实现煤层压裂全面有效增渗。基于黏聚力单元法,考虑弱固结面的产状以及与射孔的间距,建立了弱固结面水力压裂裂缝扩展模型,分析了不同弱固结面逼近角和强度下,长距比(弱固结面长度与注入点到弱固结面中心点间距的比值)对水力裂缝相交扩展规律的影响。结果表明:当长距比为1/3、2/3、1/1时,随逼近角增大,裂缝偏转角也增大;当长距比为1/3、2/3时,随逼近角增大,总缝长逐渐减小;当长距比为1/1时,随逼近角增大,总缝长逐渐增大;当逼近角≤15°时,水力裂缝与弱固结面相交后更倾向于沿弱固结面方向扩展延伸;当逼近角≥30°时,水力裂缝容易穿透弱固结面;当逼近角为30°时,缝宽最大;当弱固结面强度增大时,裂缝的偏转角和改造长度均呈增大趋势。
Coal seam reservoirs contain a large number of weakly consolidated interfaces such as cleats,bedding,and natural fractures,which,along with complex pore structures,make the prediction of fracture propagation patterns during hydraulic fracturing challenging.Understanding the intersection and expansion rules of hydraulic fractures with coal seam weakly consolidated interfaces can facilitate comprehensive and effective permeability enhancement in coal seams through fracturing.We establish a model for the expansion of hydraulic fractures on weakly consolidated interfaces based on the cohesive element method,considering the occurrence of weakly consolidated interfaces and their distance from the perforations,analyze the impact of different approach angles and strengths of weakly consolidated interfaces on the intersection and expansion patterns of hydraulic fractures at different length to distance ratios(the ratio of the weakly consolidated interface length(L)to the distance(D)from the injection point to the center of the interface).The results indicate that when the length to distance ratio(L/D)is 1/3,2/3,1/1,as the approach angle increases,so does the fracture deflection angle;when L/D is 1/3 or 2/3,the total fracture length gradually decreases with increasing approach angle;when the aspect ratio is 1/1,the total fracture length gradually increases with the increase of the approach angle;when the approach angle is≤15°,hydraulic fractures are more likely to extend along the direction of the weakly consolidated interfaces after intersection,whereas when the approach angle is≥30°,hydraulic fractures tend to penetrate the weakly consolidated interfaces;the fracture width is maximum when the approach angle is 30°;as the strength of the weakly consolidated interfaces increases,both the fracture deflection angle and the modified fracture length show an increasing trend.
作者
徐敏
孔祥伟
陈青
谢昕
张少斌
谢广宇
徐洲
XU Min;KONG Xiangwei;CHEN Qing;XIE Xin;ZHANG Shaobin;XIE Guangyu;XU Zhou(School of Petroleum Engineering,Yangtze University,Wuhan 430100,China;Hubei Key Laboratory of Oil and Gas Drilling and Production Engineering,Wuhan 430100,China;CNOOC Research Institute Co.,Ltd.,Beijing 100028,China;Institute of Oil&Gas Processing Techniques,Qinghai Oilfield Branch Company,Dunhuang 736202,China)
出处
《煤矿安全》
北大核心
2026年第1期1-10,共10页
Safety in Coal Mines
基金
中海油“十四五”规划重大资助项目(CCL2022RCPS0471RSN,CCL2022RCPS0038ESN)。
关键词
煤层压裂
黏聚力单元
裂缝相交
弱固结面
长距比
coal seam fracturing
cohesive element
fracture intersection
weakly consolidated interfaces
length-to-distance ratio
