首页|In-situ laboratory study on influencing factors of pre-SC-CO2 hybrid fracturing effect in shale oil reservoirs

In-situ laboratory study on influencing factors of pre-SC-CO2 hybrid fracturing effect in shale oil reservoirs

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Supercritical CO2(SC-CO2)fracturing,being a waterless fracturing technology,has garnered increasing attention in the shale oil reservoir exploitation industry.Recently,a novel pre-SC-CO2 hybrid fracturing method has been proposed,which combines the advantages of SC-CO2 fracturing and hydraulic frac-turing.However,the specific impacts of different pre-SC-CO2 injection conditions on the physical pa-rameters,mechanical properties,and crack propagation behavior of shale reservoirs remain unclear.In this study,we utilize a newly developed"pre-SC-CO2 injection → water-based fracturing"integrated experimental device.Through experimentation under in-situ conditions,the impact of pre-SC-CO2 in-jection displacement and volume on the shale mineral composition,mechanical parameters,and fracture propagation behavior are investigated.The findings of the study demonstrate that the pre-injection SC-CO2 leads to a reduction in clay and carbonate mineral content,while increasing the quartz content.The correlation between quartz content and SC-CO2 injection volume is positive,while a negative correlation is observed with injection displacement.The elastic modulus and compressive strength exhibit a declining trend,while Poisson's ratio shows an increasing trend.The weakening of shale mechanics caused by pre-injection of SC-CO2 is positively correlated with the injection displacement and volume.Additionally,pre-injection of SC-CO2 enhances the plastic deformation behavior of shale,and its breakdown pressure is 16.6％lower than that of hydraulic fracturing.The breakdown pressure demon-strates a non-linear downward trend with the gradual increase of pre-SC-CO2 injection parameters.Unlike hydraulic fracturing,which typically generates primary fractures along the direction of the maximum principal stress,pre-SC-CO2 hybrid fracturing leads to a more complex fracture network.With increasing pre-SC-CO2 injection displacement,intersecting double Y-shaped complex fractures are formed along the vertical axis.On the other hand,increasing the injection rate generates secondary fractures along the direction of non-principal stress.The insights gained from this study are valuable for guiding the design of preSC-CO2 hybrid fracturing in shale oil reservoirs.

Pre-CO2 hybrid fracturingFracture propagationFracture patternShale oil reservoir

Yu-Xi Zang、Hai-Zhu Wang、Bin Wang、Yong-Gang Yi、Tian-Yu Wang、Ming-Liang Shi、Gang-Hua Tian、Shou-Ceng Tian

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State Key Laboratory of Petroleum Resources and Prospecting,China University of Petro-leum(Beijing),Beijing 102249,China

Engineering Technology Research Institute of Xinjiang Oilfield Company,Karamay 834000,Xinjiang,China

State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing,102249,China

College of Petroleum,China University of Petroleum-Beijing at Karamay,Karamay,834000,Xinjiang,China

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2024

10.1016/j.petsci.2024.05.020

石油科学(英文版)
中国石油大学（北京）

石油科学(英文版)

EI
影响因子：0.88
ISSN：1672-5107
年,卷(期)：2024.21(5)