Yan Jin, Ni Xiaoming, Li Junfeng, Zhao Yanwei
School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China.
Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Jiaozuo 454000, China.
ACS Omega. 2025 Mar 7;10(10):10261-10271. doi: 10.1021/acsomega.4c09684. eCollection 2025 Mar 18.
The distribution of mobile water during slug flows in coalbed methane (CBM) wells directly affects the water pressure propagation path. In this article, the distribution characteristics of gas and water in fractures during slug flow are characterized by gas-liquid microscopic flow experiments. Fluid-structure interaction was adopted to analyze the fracture morphology after deformation under stress. A mathematical model of the critical fracture size for migration of mobile water during slug flows was established through nuclear magnetic resonance tests, contact-angle tests, and the theory of the gas-water migration equilibrium. The results show that the flow rate of the gas and liquid affects the length and period of the gas plug and slug. The gas-liquid-solid three-phase properties affect the shape of the gas-liquid boundary. When the mobile water during slug flows is transformed into bound water, the fractures are deformed to an hourglass shape. The fracture size for migration of mobile water is negatively correlated with the reservoir pressure and contact angle with a power exponent while linearly positively correlated with the surface tension. Using fracturing fluids with low surface tension and high liquid-solid contact angles can promote the expulsion of liquids from reservoir fractures, thereby achieving higher resource productivity. Mathematical statistical methods have been employed to establish a rapid calculation model for the movable water transport fracture size. In summary, the research provides an effective and accurate quantitative method of evaluation for the critical fracture size for the migration of mobile water.
煤层气井段塞流期间可动水的分布直接影响水压传播路径。本文通过气液微观流动实验表征了段塞流期间裂缝中气水的分布特征。采用流固耦合分析应力作用下变形后的裂缝形态。通过核磁共振测试、接触角测试和气水迁移平衡理论，建立了段塞流期间可动水迁移临界裂缝尺寸的数学模型。结果表明，气液流速影响气塞和段塞的长度和周期。气液固三相性质影响气液边界形状。段塞流期间可动水转变为束缚水时，裂缝变形为沙漏状。可动水迁移的裂缝尺寸与储层压力和接触角呈负幂指数相关，与表面张力呈线性正相关。使用低表面张力和高液固接触角的压裂液可促进储层裂缝中液体的排出，从而实现更高的资源产能。已采用数理统计方法建立了可动水运移裂缝尺寸的快速计算模型。总之，该研究为可动水迁移临界裂缝尺寸提供了一种有效且准确的定量评价方法。
