摘要
中国深层页岩气藏构造复杂、储层温度高和地应力差异大,致使页岩气储层压裂过程中存在起裂压力高、裂缝网络单一等问题。为此,综合超临界CO_(2)压裂(SCF)与脉冲压裂在致裂储层的优势,探索了超临界CO_(2)脉冲压裂(SCPF)对页岩裂缝起裂和扩展的影响规律。以四川盆地下志留统龙马溪组页岩为研究对象,开展了SCPF页岩的对比实验,通过声发射监测、CT扫描及三维重构技术对实验结果进行表征,揭示了不同压裂方式及脉冲参数对页岩裂缝起裂压力、扩展形态及裂缝复杂性的影响。研究结果表明:①SCPF的起裂压力相较SCF降低了16.33%,较水力压裂降低了40.95%;②SCPF使大振幅的应力释放被分散到多次小振幅事件中,可以释放更多的声发射信号,产生的声发射累计能量和起裂瞬态能量分别是SCF的2.30倍和0.83倍;③SCPF形成拉-剪混合裂缝网络,伴随大量次生裂缝和层理裂缝,裂缝扩展面积和体积分别是SCF的2.07倍和1.47倍;④在低频脉冲条件下,起裂压力随脉冲频率和振幅的增加而降低,裂缝复杂程度随脉冲频率和振幅的增加而提高。结论认为,超临界CO_(2)脉冲压裂技术能够有效改善页岩储层压裂效果,为优化页岩气开采工艺参数提供了理论与实验依据。
Deep shale gas reservoirs in China are characterized by complex structures,high reservoir temperature and varying in-situ stress,leading to high fracture initiation pressure(FIP),simple fracture networks and other problems in reservoir fracturing.By taking the shale of Lower Silurian Longmaxi Formation in the Sichuan Basin as an example and considering the advantages of supercritical CO_(2) fracturing(SCF)and pulse fracturing,the influence laws of supercritical CO_(2) pulse fracturing(SCPF)on initiation and propagation of fractures in shale were investigated.The physical simulation experiment was conducted on SCPF in shale and the experimental results were characterized using the acoustic emission monitoring,CT scanning and three-dimensional reconstruction techniques,finally,the effects of different fracturing techniques and pulse parameters on shale fracture initiation pressure,propagation pattern and complexity were revealed.The following results are obtained.First,FIP in SCPF is 16.33%lower than that in SCF and 40.95%lower than that by hydraulic fracturing.Second,SCPF enables a dispersion of stress relief at a high amplitude into multiple low-amplitude events,thus releasing more acoustic emission signals,with the generated cumulative energy of acoustic emission and transient energy of fracture initiation being 2.30 and 0.83 times that in SCF.Third,SCPF creates a network of mixed tensile and shear fractures,associated with numerous secondary fractures and bedding fractures,corresponding to the fracture propagation area and the volume being 2.07 and 1.47 times respectively that in SCF.Fourth,at a low-frequency pulse,FIP drops with the increasing pulse frequency and amplitude,and the degree of fracture complexity increases with the increasing pulse frequency and amplitude.It is concluded that SCPF can effectively improve the shale reservoir fracturing performance.This new insight provides a theoretical basis for optimizing parameters of shale gas recovery processes,thereby facilitating the beneficial development of shale gas and the high-quality growth of the industry.
作者
陆朝晖
闫卓林
王俐佳
卢义玉
房大志
周军平
LU Zhaohui;YAN Zhuolin;WANG Lijia;LU Yiyu;FANG Dazhi;ZHOU Junping(State Key Laboratory of Coal Mine Disaster Dynamics and Control//Chongqing University,Chongqing 400044,China;School of Resources and Safety Engineering,Chongqing University,Chongqing 400044,China;Sichuan Shale Gas Exploration&Production Co.,Ltd.,Neijiang,Sichuan 641199,China;Sinopec East China Oil&Gas Company,Nanjing,Jiangsu 210011,China)
出处
《天然气工业》
北大核心
2025年第9期79-91,共13页
Natural Gas Industry
基金
重庆市杰出青年科学基金项目“海相页岩气储层超临界CO_(2)阶跃式脉冲循环体积压裂及置换封存机理”(编号:cstc2021jcyj-jqX0007)
重庆市技术创新与应用发展重点项目“页岩气老井采收率提升关键技术研究与应用”(编号:CSTB2023TIADKPX0082)
“深层页岩气超临界CO_(2)复合增能压裂关键技术研究与应用”(编号:CSTB2024TIAD-KPX0086)。
关键词
深层页岩气
超临界CO_(2)
脉冲压裂
脉冲频率
脉冲振幅
疲劳损伤
起裂压力
裂缝扩展
Deep shale gas
Supercritical CO_(2)
Pulse fracturing
Pulse frequency
Pulse amplitude
Fatigue damage
Fracture initiation pressure(FIP)
Fracture propagation
