Huang Fansheng, Wang Fengbin, Sang Shuxun, Liu Shiqi, You Zhenjiang
Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization, China University of Mining and Technology, Xuzhou 221008, China.
Carbon Neutrality Institute, China University of Mining and Technology, Xuzhou 221008, China.
ACS Omega. 2024 Jul 15;9(29):32066-32079. doi: 10.1021/acsomega.4c04121. eCollection 2024 Jul 23.
Hydraulic fracturing is a widely used technique to enhance the production of coalbed methane reservoirs. However, a common issue is the invasion of coal fines into proppant packs, leading to pore clogging and reduced conductivity. This study investigated the impact of flow velocity on clogging by coal fines in saturated proppant packs to optimize the flow velocity and alleviate clogging during dewatering. Clogging experiments induced by coal fines were conducted on saturated proppant packs with varying superficial velocities. Throughout each experiment, the permeability and effluent concentration were monitored, and the process of clogging was visually observed using an optical microscope. The experimental results showed that both permeability and effluent concentration initially increased and then decreased with an increase in flow velocity, indicating the existence of a critical flow velocity for minimizing clogging in proppant packs. Microscale observations revealed that the dominant regimes of clogging induced by coal fines at low and high flow velocities were surface deposition and hydrodynamic bridging, respectively; a critical flow velocity was required to induce the occurrence of bridging. Removal efficiencies of coal fines in relation to surface deposition and straining against flow velocity were theoretically analyzed, aiming to provide insights into the mechanisms underlying the impact of flow velocity on clogging. The results showed that the overall removal efficiency by surface deposition and straining decreased with an increase in flow velocity. Theoretical data matched well with the experimental results at low flow velocities but failed to explain the outcomes at high flow velocities, primarily due to the onset of bridging at high flow velocities. This study highlights the necessity of developing a removal efficiency model for bridging to accurately describe clogging by coal fines in proppant packs and provides recommendations for clogging control in proppant packs.
水力压裂是一种广泛应用于提高煤层气藏产量的技术。然而，一个常见的问题是煤粉侵入支撑剂填充层，导致孔隙堵塞和导流能力降低。本研究调查了流速对饱和支撑剂填充层中煤粉堵塞的影响，以优化流速并减轻脱水过程中的堵塞。在具有不同表观流速的饱和支撑剂填充层上进行了由煤粉引起的堵塞实验。在每个实验过程中，监测渗透率和流出物浓度，并使用光学显微镜直观地观察堵塞过程。实验结果表明，渗透率和流出物浓度最初随流速增加而增加，然后随流速增加而降低，这表明存在一个临界流速，可使支撑剂填充层中的堵塞最小化。微观尺度观察表明，在低流速和高流速下，由煤粉引起的堵塞主要机制分别是表面沉积和流体动力桥接；需要一个临界流速来引发桥接的发生。从理论上分析了煤粉相对于表面沉积和流速过滤的去除效率，旨在深入了解流速对堵塞影响的潜在机制。结果表明，表面沉积和过滤的总体去除效率随流速增加而降低。理论数据在低流速下与实验结果吻合良好，但无法解释高流速下的结果，主要是因为在高流速下会出现桥接现象。本研究强调了开发桥接去除效率模型以准确描述支撑剂填充层中煤粉堵塞的必要性，并为支撑剂填充层中的堵塞控制提供了建议。
