College of Water Resource & Hydropower, Sichuan University
Shale Gas Research Institute, PetroChina Southwest Oil & Gas Field Company
Sino-German Energy Research Center, Sichuan University

页岩气开发需要通过水力压裂技术形成缝网系统,为了研究天然裂缝特征对页岩储层渗流的影响,基于页岩储层中的质量守恒定律、朗格缪尔吸附方程及达西定律等,推导出了用于描述储层压裂区域内气体渗流行为的数学模型;基于该数学模型对引入的嵌入离散裂缝模型进行数值模拟,将模拟结果与已有文献结果,以及与现场实际生产数据进行对比,验证了模型的正确性;并在不同的天然裂缝渗透率、密集度、倾斜角组合情况下进行了页岩储层渗流数值模拟,研究了不同天然裂缝特征组合对页岩储层渗流的影响。研究结果表明:该数学模型能较好地模拟出储层情况,改变天然裂缝渗透率、密集度、倾斜角等参数均对页岩储层渗流行为有明显影响,增加天然裂缝渗透率会加大倾斜角、密集度对储层渗流的影响,对产气量的影响约10%;增加密集度会加大渗透率对储层渗流的影响,减小倾斜角对储层渗流的影响,对产气量的影响约6.3%;增大倾斜角会同时减小密集度、渗透率对储层渗流的影响,此现象可能是由于天然裂缝与水力裂缝交叉位置数量降低所致。该成果一方面可加深对不同天然裂缝特征组合与储层渗流潜在联系的科学认识;另一方面,所描述的天然裂缝特征的影响规律可对设计水力压裂施工方案、提高储层产量提供参考。

In the process of shale gas recovery, hydraulic fracturing technology is needed to form fracture net-work system. In order to study the influence of natural fracture characteristics on the seepage in shale reservoirs, this paper derives a mathematical model for describing the gas seepage behavior in the fractured area of the reservoir based on the law of mass conservation in shale reservoirs, the Langemuir adsorption equation and Darcy's law, etc. The mathematical model is used to describe the gas seepage behavior in the fractured area of reservoir; Numerical simulation with the introduced embedded discrete fracture model is performed based onthis mathematical model, and the model is verified by comparing the simulation results with the existing litera-ture data, as well as the actual production data on site; The verified model is used to investigate gas flow behav-ior influenced by natural fractures, where the permeability, densities and orientation are proved to have an ob-vious effect on seepage behavior. Increasing the natural fracture permeability amplifies the effects of inclina-tion angle and fracture density on reservoir flow, and the maximum of influence reaches about 10%. The higher fracture density enhances the impact of permeability while weakening the influence of inclination angle on res-ervoir flow, and the maximum of influence reaches about 6.3%. Moreover, an increase in the inclination angle simultaneously reduces the effects of density and permeability on reservoir flow, potentially due to a decrease in the number of intersections between natural and hydraulic fractures. On the one hand, the results deepen the scientific understanding of the potential connection between different combinations of natural fracture charac-teristics and reservoir seepage; on the other hand, the described laws of the influence of natural fracture charac-teristics are of great significance for the design of hydraulic fracturing construction programs and the enhance-ment of reservoir production.

国家自然科学基金资助项目(U20A20266,12302503);四川省科技计划资助项目(2023ZYD0154,2024GJHZ0035)

1数学模型
1.1渗流场方程
1.2变形场方程
2模型验证
2.1 DFM方法验证
2.2现场验证
3不同天然裂缝特征组合的影响
3.1渗透率及密集度的影响
3.2渗透率及倾斜角的影响
3.3密集度及倾斜角的影响
4结论

刘建锋, 何鑫, 薛福军, 等. 天然裂缝多特征组合对页岩储层渗流的影响[J]. 采矿与岩层控制工程学报, 2024, 6(1): 013437.

LIU Jianfeng, HE Xin, XUE Fujun, et al. The influence of natural fractures of multi-feature combination on seepage behavior in shale reservoirs[J]. Journal of Mining and Strata Control Engineering, 2024, 6(1): 013437.