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首页» 本刊导读 944-959     DOI : 10.3969/j.issn.2096-1693.2024.06.073
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超深高应力差储层近井筒裂缝扩展转向机理研究
韦世明, 张亚洲, 金衍
1 中国石油大学( 北京) 理学院,北京 102249 2 中国石油大学( 北京) 油气资源与工程全国重点实验室,北京 100049 3 中国石油大学( 北京) 石油工程学院,北京 102249
Study on the mechanism of fracture propagation and deflection near wellbore in ultra-deep high stress difference reservoir
WEI Shiming, ZHANG Yazhou, JIN Yan
1 College of Science, China University of Petroleum-Beijing, Beijing 102249, China 2 State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum-Beijing, Beijing 102249, China 3 College of Petroleum Engineering, China University of Petroleum-Beijing, Beijing 102249, China

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摘要  随着油气勘探开发进入超深层,高应力差条件下水力裂缝扩展易发生大曲率转向,井口超压、砂堵等问题频发,明确超深高应力差储层近井筒水力裂缝的扩展与转向机理与主控因素,对超深层储层安全高效开发具有重要意义。在经典热力学的连续性框架约束下,将离散界面的尖锐裂缝平滑描述为连续损伤的弥散裂缝,利用Griffith能量平衡关系和断裂变分原理构建Lagrange能量泛函,并基于能量最小化原理建立了各向异性储层中射孔井的相场水力压裂模型。通过对比经典的Griffith尖锐裂纹轮廓方程,证实了本文相场模型的正确性。总结模拟结果发现,水力裂缝沿着射孔与最大水平主应力之间的某个方位近似直线起裂,而后向最大水平主应力方向偏转,具体起裂方位受地应力差、排量及射孔角度影响。地应力差的增大会促进近井筒水力裂缝转向扩展,使得转向角增加、转向半径减小;增大排量可减弱水力裂缝转向,使得转向角减小、转向半径增加,促使裂缝沿起裂阶段的直线扩展地更远,并能显著提高裂缝扩展速率;随着射孔角增加,射孔与最大水平主应力夹角增大,会加剧裂缝扩展的偏转程度,使得转向角增大、转向半径减小,从而造成压裂液流动摩阻上升以及砂堵风险的提高;储层的各向异性特征也能显著影响水力裂缝的转向扩展过程,模型中以不同方向上的临界能量释放率作为断裂阻力的各向异性参数,结果表明,裂缝更倾向于沿低阻力的方向扩展,断裂阻力的各向异性越强,水力裂缝的偏转程度也就越大,储层断裂的各向异性特征显著影响裂缝的转向行为。本文的相场水力压裂模型提供了一个无需任何断裂准则的水力裂缝扩展与转向行为研究的便捷方法,有助于提升超深高应力差储层近井裂缝转向认识,帮助理解不同地质环境和压裂工况下的断裂机理与裂缝偏转行为,并为压裂工艺设计与射孔方案优化提供参考和建议。
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关键词 : 超深层,高应力差,水力裂缝,扩展转向,相场法
Abstract

With the exploration and development of oil and gas into the ultra-deep reservoir, hydraulic fracture propagation under the condition of high stress difference is prone to occur large curvature deflection, leading to wellhead overpressure, sand plugging and other problems occur frequently. It is of great significance to clarify the mechanism and main control factors of hydraulic fracture propagation and deflection near wellbore in ultra-deep and high stress difference reservoir for safe and efficient development. Under the constraint of the continuity framework of classical thermodynamics, the sharp fracture on the discrete interface is smoothly described as a continuous damage dispersion fracture, and the Lagrange Energy Functional is constructed based on Griffith energy balance relation and fracture variational principle, and then the phase field hydraulic fracturing model of perforated well in anisotropic reservoir is established based on the principle of energy minimization. The validity of the phase-field model presented in this paper is verified by comparing with the classical Griffith crack opening profile equation. It is found that the hydraulic fracture starts to crack along an approximate straight line between perforation and maximum horizontal principal stress, and then deflects to the maximum horizontal principal stress direction. The specific direction of crack initiation is affected by in-situ stress difference, displacement and perforation angle. The increase of the in-situ stress difference will promote the hydraulic fracture deflection propagation near the wellbore, make the deflection angle increase and the deflection radius decrease; increasing the displacement can weaken the hydraulic fracture deflection, and making the deflection angle decrease and the deflection radius increase; with the increase of perforation angle, the angle between perforation and the maximum horizontal principal stress increases, which will aggravate the deflection degree of crack propagation so that the flow friction of fracturing fluid increases and the risk of sand plugging increases; the anisotropy characteristics of the reservoir can also significantly affect the deflection and propagation process of hydraulic fractures. In the model, the critical energy release rate in different directions is taken as the anisotropic parameter of fracture resistance. The results show that fractures tend to propagate in the direction of low resistance. The stronger the anisotropy of fracture resistance, the greater the deflection degree of hydraulic fractures. The anisotropic characteristics of reservoir fractures significantly affect the turning behavior of fractures. The phase-field hydraulic fracturing model in this paper provides a convenient method to study the propagation and steering behavior of hydraulic fractures without any fracture criteria, which is helpful to improve the understanding of near-well fracture steering in ultra-deep and high stress difference reservoirs, help to understand the fracture mechanism and fracture deflection behavior under different geological environments and fracturing conditions, and provide reference and suggestions for fracturing technology design and perforation scheme optimization.


Key words: ultra-deep reservoir; high stress difference; hydraulic fracture; deflection and propagation; phase field method
收稿日期: 2024-12-30     
PACS:    
基金资助:国家自然科学基金青年科学基金项目(42407252)、国家自然科学基金重点项目(52334001) 和中国石油大学( 北京) 青年拔尖人才项目(2462023BJRC007)联合资助
通讯作者: jiny@cup.edu.cn
引用本文:   
韦世明, 张亚洲, 金衍. 超深高应力差储层近井筒裂缝扩展转向机理研究. 石油科学通报, 2024, 09(06): 944-959 WEI Shiming, ZHANG Yazhou, JIN Yan. Study on the mechanism of fracture propagation and deflection near wellbore in ultra-deep high stress difference reservoir. Petroleum Science Bulletin, 2024, 09(06): 944-959.
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