Effect of CO2 pre-fracturing on fracture networks in shale oil reservoirs

doi:10.3969/j.issn.1006-6535.2026.02.008

Abstract

Abstract: To investigate the influence of CO₂ pre-fracturing on the scale and morphology of fracture networks in shale oil reservoirs,a three-dimensional geological model that includes natural fractures was constructed using Petrel software,based on the reservoir characteristics of a shale oil formation in the Dongying Sag.By using the fracture network volume and network complexity as evaluation indices of fracturing effectiveness,analysis was made on the impact of CO₂ pre-injection volumes on these indices under different natural fracture densities and horizontal stress differences.The results showed that natural fracture density had little effect on fracture network volume;increasing CO₂ injection volume first reduced and then increased the network volume,with a sharp increase occurring once the CO₂ injected per stage exceeded about 120 t which point the low viscosity and high diffusivity of CO₂ dominated.Higher natural fracture density led to higher network complexity;in reservoirs with well-developed natural fractures,increasing CO₂ injection caused network complexity to rise and then level off.Horizontal stress difference significantly affected network complexity:branching fractures formed more readily under low stress-difference conditions.This study provides theoretical guidance for designing horizontal-well CO₂ pre-fracturing in shale oil reservoirs.

Key words: CO₂ pre-fracturing, shale oil reservoir, natural fracture, horizontal stress difference, fracture network volume, fracture network complexity

CLC Number:

TE357

CUI Chuanzhi, QIAN Yin, WU Zhongwei, WANG Junkang, ZHANG Shiming, LYU Qi, CHENG Ziyan. Effect of CO₂ pre-fracturing on fracture networks in shale oil reservoirs[J]. Special Oil & Gas Reservoirs, 2026, 33(2): 72-78.

References

[1] 雷群,翁定为,熊生春,等.中国石油页岩油储集层改造技术进展及发展方向[J].石油勘探与开发,2021,48(5):1035-1042.
LEI Qun,WENG Dingwei,XIONG Shengchun,et al.Progress and development directions of shale oil reservoir stimulation technology of China national petroleum corporation[J].Petroleum Exploration and Development,2021,48(5):1035-1042.
[2] 雷群,胥云,才博,等.页岩油气水平井压裂技术进展与展望[J].石油勘探与开发,2022,49(1):1-8.
LEI Qun,XU Yun,CAI Bo,et al.Progress and prospects of horizontal well fracturing technology for shale oil and gas reservoirs[J].Petroleum Exploration and Development,2022,49(1):1-8.
[3] 杨勇.济阳陆相断陷盆地页岩油富集高产规律[J].油气地质与采收率,2023,30(1):1-20.
YANG Yong.Enrichment and high production regularities of shale oil reservoirs in continental rift basin:a case study of Jiyang Depression,Bohai Bay Basin[J].Petroleum Geology and Recovery Efficiency,2023,30(1):1-20.
[4] 卢义玉,廖引,汤积仁,等.页岩超临界CO₂压裂起裂压力与裂缝形态试验研究[J].煤炭学报,2018,43(1):175-180.
LU Yiyu,LIAO Yin,TANG Jiren,et al.Experimental study on fracture initiation pressure and morphology in shale using supercritical CO₂ fracturing[J].Journal of China Coal Society,2018,43(1):175-180.
[5] 罗攀,孙晓,贺沛,等.CO₂与清水的压裂特征对比[J].大庆石油地质与开发,2023,42(4):90-98.
LUO Pan,SUN Xiao,HE Pei,et al.Fracturing characteristics comparison of CO₂ and fresh water[J].Petroleum Geology & Oilfield Development in Daqing,2023,42(4):90-98.
[6] 邹雨时,李彦超,李四海.CO₂前置注入对页岩压裂裂缝形态和岩石物性的影响[J].天然气工业,2021,41(10):83-94.
ZOU Yushi,LI Yanchao,LI Sihai.Influence of CO₂ pre-injection on fracture morphology and the petrophysical properties in shale fracturing[J].Natural Gas Industry,2021,41(10):83-94.
[7] 郭兴,孙晓,穆景福,等.超临界CO₂压裂缝内支撑剂运移规律[J].钻井液与完井液,2022,39(5):629-637.
GUO Xing,SUN Xiao,MU Jingfu,et al.Proppant migration in fracture fractured with supercritical CO₂ fracturing fluid[J].Drilling Fluid & Completion Fluid,2022,39(5):629-637.
[8] 赵坤,李泽阳,刘娟丽,等.吉木萨尔页岩油井区CO₂前置压裂工艺参数优化及现场实践[J].油气藏评价与开发,2024,14(1):83-90.
ZHAO Kun,LI Zeyang,LIU Juanli,et al.Parameter optimization and field practice of CO₂ pre-fracturing process in Jimsar shale oil block[J].Petroleum Reservoir Evaluation and Development,2024,14(1):83-90.
[9] 张矿生,齐银,薛小佳,等.鄂尔多斯盆地页岩油水平井CO₂区域增能体积压裂技术[J].石油钻探技术,2023,51(5):15-22.
ZHANG Kuangsheng,QI Yin,XUE Xiaojia,et al.CO₂ regional enhanced volumetric fracturing technology for shale oil horizontal wells in Ordos Basin[J].Petroleum Drilling Techniques,2023,51(5):15-22.
[10] 杨勇,张世明,吕琦,等.济阳坳陷古近系沙四段——沙三段页岩油立体评价探索与实践[J].中国石油勘探,2024,29(3):31-44.
YANG Yong,ZHANG Shiming,LYU Qi,et al.Research and practice of stereoscopic evaluation of shale oil in the fourth-third member of the Paleogene Shahejie Formation in Jiyang Depression[J].China Petroleum Exploration,2024,29(3):31-44.
[11] 臧雨溪,王海柱,王斌,等.鄂尔多斯盆地页岩油储层前置CO₂压裂流体分布特征[J].西安石油大学学报(自然科学版),2024,39(2):55-61.
ZANG Yuxi,WANG Haizhu,WANG Bin,et al.Fluid distribution characteristics in CO₂ fracturing for shale oil reservoirs in Ordos Basin[J].Journal of Xi′an Shiyou University (Natural Science Edition),2024,39(2):55-61.
[12] DERSHOWITZ W S,HERDA H H.Interpretation of fracture spacing and intensity[C]//TILLERSON J R,WAWERSIK W R.Rock mechanics.Rotterdam:Balkema,1992:757-766.
[13] WENG X,KRESSE O,COHEN C,et al.Modeling of hydraulic-fracture-network propagation in a naturally fractured formation[J].SPE Production & Operations,2011,26(4):368-380.
[14] LEE T C,KASHYAP R L,CHU C N.Building skeleton models via 3-D medial surface axis thinning algorithms[J].Graphical Models and Image Processing,1994,56(6):462-478.
[15] KERSCHNITZKI M,KOLLMANNSBERGER P,BURGHAMMER M,et al.Architecture of the osteocyte network correlates with bone material quality[J].Journal of Bone & Mineral Research,2013,28(8):1837-1845.
[16] 李阳,祝仰文,李宗阳,等.济阳坳陷页岩油注二氧化碳开发技术[J].石油勘探与开发,2024,51(4):855-864.
LI Yang,ZHU Yangwen,LI Zongyang,et al.Shale oil recovery by CO₂ injection in Jiyang Depression,Bohai Bay Basin,east China[J].Petroleum Exploration and Development,2024,51(4):855-864.

Effect of CO₂ pre-fracturing on fracture networks in shale oil reservoirs

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