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首页» 过刊浏览» 2020» Vol.5» Issue(2) 239-253     DOI : 10.3969/j.issn.2096-1693.2020.02.021
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超临界 CO2 压裂诱导裂缝机理研究综述
周大伟,张广清
中国石油大学(北京)石油工程学院,北京 102249
A review of mechanisms of induced fractures in SC-CO2 fracturing
ZHOU Dawei, ZHANG Guangqing
College of Petroleum Engineering, China University of Petroleum-Beijing, Beijing 102249, China

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摘要  超临界二氧化碳(SC-CO2)压裂改造非常规储层具有提高油气产量、储层无污染、节约水资源、埋存CO2 等优点,受到了工业界和学术界的广泛关注。本文综述了目前室内SC-CO2 压裂实验方法、裂缝起裂扩展特征与 机理,以及存在的问题并给出建议。SC-CO2 与岩石的“热(T)—流(H)—力(M)—化(C)”多场耦合作用机理为诱 导应力和弱化断裂性质两方面。诱导应力方面包括:SC-CO2 低黏度和高扩散性导致的孔隙压力场和热应力场, 共同降低有效应力并诱发天然裂缝的剪切破坏(TH-M);SC-CO2 相变释放的能量以冲击载荷和热应力的形式促 进裂缝动态扩展(TH-M)。弱化断裂性质方面包括:零表面张力的SC-CO2 可进入微裂纹尖端,降低裂缝扩展所 需的缝内净压力(H-M);SC-CO2 吸附在微裂纹表面,降低裂缝失稳扩展所需的临界应力(C-M)。因此,SC-CO2 压裂易于形成以I-II混合型破坏为主的多裂缝,适合改造裂缝性致密储层。未来应积极开展SC-CO2 三维裂缝扩 展实验模拟,进行裂缝特征重构和定量评价,利用理论模型和数值模拟研究方法,实现研究尺度的升级,加快 SC-CO2 压裂工业应用进程。
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关键词 : SC-CO2 压裂;裂缝形成机理;实验研究;THMC耦合;非常规油气
Abstract
In unconventional reservoir stimulation, Supercritical (SC) CO2 fracturing can not only increase oil/gas production, minimize formation damage and conserve water resources, but also promote CO2 geological storage, which draws broad attention in both industry and academia. This work reviewed the current studies with respect to experimental techniques, characteristics and mechanisms of fracture initiation and propagation, and related existing problems and suggestions in SC-CO2 fracturing. The mechanisms of coupled thermo-hydro-mechanical-chemical (THMC) processes between SC-CO2 and rockare induced stress and weakened fracture toughness. The induced stress includes the thermal stress and pore pressure field induced by the low viscosity and high diffusionof SC-CO2, which can lower the effective stress and even create shear failure (TH-M effects). Thedynamic load and thermal stress created by the SC-CO2 phase change can enhance micro-fracture initiation and propagation (TH-M effects). The weakened fracture toughness includes SC-CO2 of zero surface tension, tending to penetrate into the micro-cracks to lower fracture net pressure for crack growth (H-M effects). CO2 adsorption can lower the surface energy of rock and this in turn reduces the critical stress for crack growth (C-M effects). Therefore, SC-CO2 fracturing tends to create multiple fractures characterized by I-II type failure, which can be applied for stimulation of fracturedtight reservoirs. So, in the future, it will be necessary to conduct SC-CO2 fracturing experiments, to be used to reconstruct and evaluate the induced 3D fractures. The research scale is upgraded
with the theoretical and numerical models to accelerate the process of SC-CO2 fracturing in the field.

 

Key words: SC-CO2 fracturing; fracture mechanism; experimental study; THMC coupling; unconventional reservoirs
收稿日期: 2020-06-30     
PACS:    
基金资助:国家杰出青年科学基金(51925405)、国家自然科学基金面上项目(51774299) 和国家科技重大专项(2016ZX05046-04, 2016ZX05050,
2017ZX05069) 联合资助
通讯作者: zhangguangqing@cup.edu.cn
引用本文:   
ZHOU Dawei, ZHANG Guangqing. A review of mechanisms of induced fractures in SC-CO2 fracturing. Petroleum Science Bulletin, 2020, 02: 239-253.
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