油气藏评价与开发 ›› 2023, Vol. 13 ›› Issue (6): 834-843.doi: 10.13809/j.cnki.cn32-1825/te.2023.06.015

• 综合研究 • 上一篇    下一篇

连续加载应力下真实裂缝流场和渗透率演化规律数值研究

梁运培1,2(),张怀军1,2,王礼春3,秦朝中1,2,田键1,2(),陈强1,2,史博文1,2   

  1. 1.重庆大学煤矿灾害动力学与控制全国重点实验室,重庆 400044
    2.重庆大学资源与安全学院,重庆 400044
    3.天津大学表层地球系统科学研究院,天津 300072
  • 收稿日期:2023-01-18 发布日期:2024-01-03 出版日期:2023-12-26
  • 通讯作者: 田键(1990—),男,博士,助理研究员,主要从事非常规油气储层保护与开发、复杂多孔介质微观渗流方面的相关科研工作。地址:重庆市沙坪坝区沙正街174号重庆大学A区,邮政编码:400044。E-mail:tianjian2171@cqu.edu.cn
  • 作者简介:梁运培(1971—),男,博士,教授,主要从事非常规天然气开发、煤矿瓦斯灾害防治等方面的科研与教学工作。地址:重庆市沙坪坝区沙正街174号重庆大学A区,邮政编码:400044。E-mail:liangyunpei@cqu.edu.cn
  • 基金资助:
    国家自然科学基金项目“多重非对称采动卸压边界动态演化特征及对瓦斯运移影响机制”(52174166);国家自然科学基金项目“自发渗吸微观动力学特性及其在两相达西模型中的量化”(127072053);中国博士后面上项目“孔隙尺度气-水界面演化对致密砂岩气流动作用机理研究”(2021M700606)

Numerical simulation of flow fields and permeability evolution in real fractures under continuous loading stress

LIANG Yunpei1,2(),ZHANG Huaijun1,2,WANG Lichun3,QIN Chaozhong1,2,TIAN Jian1,2(),CHEN Qiang1,2,SHI Bowen1,2   

  1. 1. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
    2. School of Resources and Safety Engineering, Chongqing University, Chongqing 400044, China
    3. Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China
  • Received:2023-01-18 Online:2024-01-03 Published:2023-12-26

摘要:

采用数值随机生成的裂缝研究有效应力作用下裂缝导流能力变化忽视了真实裂缝开度非均质性的影响。研究采用巴西劈裂法对不同种类岩石造缝获取真实裂缝样品,使用三维光学扫描仪提取真实裂缝形貌特征及裂缝开度信息,建立接触力学模型和单相渗流模型,开展了有效应力连续加载下的裂缝流场和渗透率演化行为数值研究,并分析了传统的经验公式对真实裂缝案例的适应性。结果表明:①巴西劈裂的25 mm×50 mm真实裂缝在原始开度、表面粗糙度等微观结构上具有非均质性强特征,与直接通过数值生成的达到平均化尺度的裂缝存在明显不同;②由于非均质性的影响,不同岩石裂缝在有效应力加载过程中的裂缝开度、接触面积和空间相关长度在x方向和y方向上的演化行为有显著区别,且对渗透率变化的控制机理不同;③采用传统的经验公式拟合裂缝应力敏感渗透率演化时,拟合程度随着裂缝样品的非均质性增加而出现偏差增大。研究认为,传统经验公式在研究达到平均化尺度的裂缝时具有较好的应用基础,但针对非均质性强或整体未能满足平均化裂缝的应用受限。

关键词: 裂缝, 应力, 渗透率演化, 非均质性, 数值模拟

Abstract:

In the study of fracture conductivity evolution under stress using direct numerically generated fracture models, a key issue is the neglect of the real fracture's heterogeneous microstructure. To address this, the Brazilian splitting method is used to create fractures in various types of rocks. A 3D optical topography scanner then captures the actual fracture morphology and aperture information. This data forms the basis for establishing a contact mechanics model and a single-phase seepage model, which are used to study the evolution of the fracture flow field and permeability under continuous stress loading. The study also evaluates the applicability of traditional empirical formulas to real fracture cases. The findings are significant: ① The 25 mm×50 mm real fracture in Brazilian splitting shows obvious heterogeneity in the microstructure of the original aperture and surface roughness, which is obviously different from the fracture that reaches the average scale directly generated by numerical method. ② In the process of stress loading, the fracture aperture, contact area and spatial correlation length show different evolution characteristics in the x direction and y direction due to the fracture heterogeneity, and the control mechanism of permeability change is different; ③ When the traditional empirical formula is used to fit the stress-sensitive permeability evolution of fracture, the deviation of the fitting degree increases with the increase of the heterogeneity of fracture samples. This study suggested that the traditional empirical formula has a good application basis in the study of the fracture reaching the averaging scale, but it is limited in the application of the fracture with strong heterogeneity or failure to meet the averaging scale.

Key words: fracture, stress, permeability evolution, heterogeneity, numerical simulation

中图分类号: 

  • TE377