天然气工业2025，Vol.45Issue(9)：79-91,13.DOI:10.3787/j.issn.1000-0976.2025.09.007
超临界CO2脉冲致裂页岩裂缝起裂及扩展影响规律
Influence laws of supercritical CO2 pulse fracturing on initiation and propagation of fractures in shale:An experimental study and discussion
摘要
Abstract
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 CO2 fracturing(SCF)and pulse fracturing,the influence laws of supercritical CO2 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.关键词
深层页岩气/超临界CO2/脉冲压裂/脉冲频率/脉冲振幅/疲劳损伤/起裂压力/裂缝扩展Key words
Deep shale gas/Supercritical CO2/Pulse fracturing/Pulse frequency/Pulse amplitude/Fatigue damage/Fracture initiation pressure(FIP)/Fracture propagation分类
能源科技引用本文复制引用
陆朝晖,闫卓林,王俐佳,卢义玉,房大志,周军平..超临界CO2脉冲致裂页岩裂缝起裂及扩展影响规律[J].天然气工业,2025,45(9):79-91,13.基金项目
重庆市杰出青年科学基金项目"海相页岩气储层超临界CO2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:CSTB2023TIAD-KPX0082)、"深层页岩气超临界CO2复合增能压裂关键技术研究与应用"(编号:CSTB2024TIAD-KPX0086). （编号:cstc2021jcyj-jqX0007）
