Thermally-induced cracking behaviors of coal reservoirs subjected to cryogenic liquid nitrogen shock

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外文摘要：The benefits of using cryogenic liquid nitrogen shock to enhance coal permeability have been confirmed from experimental perspectives.In this paper,we develop a fully coupled thermo-elastic model in combination with the strain-based isotropic damage theory to uncover the cooling-dominated cracking behaviors through three typical cases,i.e.coal reservoirs containing a wellbore,a primary fracture,and a natural fracture network,respectively.The progressive cracking processes,from thermal fracture initi-ation,propagation or cessation,deflection,bifurcation to multi-fracture interactions,can be well captured by the numerical model.It is observed that two hierarchical levels of thermal fractures are formed,in which the number of shorter thermal fractures consistently exceeds that of the longer ones.The effects of coal properties related to thermal stress levels and thermal diffusivity on the fracture morphology are quantified by the fracture fractal dimension and the statistical fracture number.The induced fracture morphology is most sensitive to changes in the elastic modulus and thermal expansion coefficient,both of which dominate the complexity of the fracture networks.Coal reservoir candidates with preferred thermal-mechanical properties are also recommended for improving the stimulation effect.Further findings are that there exists a critical injection temperature and a critical in-situ stress difference,above which no thermal fractures would be formed.Preexisting natural fractures with higher density and preferred orientations are also essential for the formation of complex fracture networks.The obtained results can provide some theoretical support for cryogenic fracturing design in coal reservoirs.

外文关键词：

Coal reservoirsCryogenic shockThermal cracking behaviorsFracture morphology

作者：

Songcai Han、Qi Gao、Xinchuang Yan、Lile Li、Lei Wang、Xian Shi、Chuanliang Yan、Daobing Wang

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作者单位：

College of Energy,Chengdu University of Technology,Chengdu,610059,China

School of Engineering,The University of Western Australia,35 Stirling Highway,Perth,WA,6009,Australia

School of Petroleum Engineering,China University of Petroleum(East China),Qingdao,266580,China

School of Mechanical Engineering,Beijing Institute of Petrochemical Technology,Beijing,102617,China

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基金：

Natural Science Foundation of Sichuan,ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of China

项目编号：

2022NSFSC1227U176221651574270

出版年：

2024

DOI：

10.1016/j.jrmge.2023.12.018

岩石力学与岩土工程学报(英文版)

中国科学院武汉岩土力学所中国岩石力学与工程学会武汉大学

岩石力学与岩土工程学报(英文版)

CSTPCD

影响因子：0.404

ISSN：1674-7755

年,卷(期)：2024.16(8)