• 论文
主办单位:煤炭科学研究总院有限公司、中国煤炭学会学术期刊工作委员会
压裂液矿化度对支撑裂缝及裂隙内煤粉运移的影响
  • Title

    Impact of salinity of fracturing fluid on the migration of coal fines in propped fractures and cleats

  • 作者

    皇凡生桑树勋刘世奇陈强周效志王猛

  • Author

    HUANG Fansheng;SANG Shuxun;LIU Shiqi;CHEN Qiang;ZHOU Xiaozhi;WANG Meng

  • 单位

    中国矿业大学 江苏省煤基温室气体减排与资源化利用重点实验室中国矿业大学 碳中和研究院中国矿业大学 资源与地球科学学院重庆大学 煤矿灾害动力学与控制国家重点实验室

  • Organization
    Jiangsu Key Laboratory of Coal-based Greenhouse Gas Control and Utilization, China University of Mining and Technology
    Carbon Neutrality Institute, China University of Mining and Technology
    School of Resources and Geosciences, China Universityof Mining and Technology
    State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University
  • 摘要

    在煤层气井水力压裂阶段,支撑裂缝内煤粉沉积以及裂隙内煤粉运移,将导致支撑裂缝和裂隙渗透率降低,影响水力压裂改造效果以及后续的煤层气井排采效果。为有效疏通支撑裂缝并避免裂隙堵塞,从优化压裂液矿化度的视角,提出了水力压裂阶段支撑裂缝及裂隙内煤粉防控新方法。基于石英砂充填柱和无烟煤样,分别开展了矿化度逐级递减条件下支撑裂缝及裂隙内煤粉运移实验,分析了煤粉运移对矿化度变化的响应特征;采用扩展Derjaguin-Landau-Verwey-Overbeek(DLVO) 理论对煤粉运移进行了模拟,揭示了矿化度对煤粉运移的影响机制;并在此基础上,探究了兼顾支撑裂缝及裂隙内煤粉防控的最优矿化度范围。研究结果表明:支撑裂缝及裂隙内煤粉运移均存在临界矿化度现象,当矿化度低于临界矿化度时,支撑裂缝渗透率急剧增大,裂隙渗透率骤然降低,并伴有大量的煤粉产出;支撑裂缝内煤粉运移临界矿化度高于裂隙内煤粉运移临界矿化度,支撑剂表面电负性强于裂隙,而其疏水性弱于裂隙,是导致支撑裂缝内煤粉运移临界矿化度偏高的主要原因;随矿化度的逐级降低,煤粉与通道间的双电层斥力不断增大,当矿化度降至临界矿化度时,双电层斥力开始大于Lifshitz-van der Waals 引力和Lewis 酸碱引力之和,诱发煤粉运移;理论模型预测的支撑裂缝及裂隙内煤粉运移临界矿化度均与实验结果一致,证实了模型的可靠性。在水力压裂阶段,可将压裂液矿化度设计在支撑裂缝与裂隙内煤粉运移临界矿化度之间,从而促使支撑裂缝内煤粉产出,并抑制裂隙内煤粉运移,达到兼顾支撑裂缝及裂隙内煤粉防控的目的。

  • Abstract
    During the hydraulic fracturing of coalbed methane (CBM) well, the deposition of coal fines in propped fracturesand the migration of coal fines in cleats will damage the permeabilities of propped fractures and cleats, consequently affecting the hydraulic fracturing and the subsequent drainage of CBM well. For the purpose of dredging propped fracturesand avoiding the clogging of cleats effectively, a novel method for the control of coal fines in propped fractures andcleats during hydraulic fracturing was proposed by optimizing the salinity of fracturing fluid. With the salinity decreasingstepwise, the experiments on the migration of coal fines in propped fractures and cleats were conducted on quartz sandpackedcolumns and anthracite coal plugs, respectively, to investigate the response characteristics of the migration of coalfines to the change of salinity. Additionally, the migration of coal fines was simulated by using the extended DLVO method,to elucidate the influence mechanisms of salinity on the migration of coal fines. On this basis, the optimal salinityrange that takes into account the control of coal fines in propped fractures and cleats was explored. The results indicatedthat there existed a critical salt concentration (CSC) for the migration of coal fines in both propped fractures and cleats.When the salinity was lower than the CSC, the permeability of propped fractures abruptly increased while that of cleats decreasedsharply, accompanied by a large amount of coal fines produced. The value of the CSC for the migration of coalfines in propped fractures was higher than that in cleats, which can be attributed to the fact that the surface electronegativityof proppants was stronger than that of cleats, while the hydrophobicity was weaker than that of cleats. With the gradualdecrease of salinity, the electric double layer (EDL) repulsive force between coal fines and channel increased continuously.When the salinity decreased to the CSC, the EDL repulsion started to be greater than the sum of Lifshitz-van derWaals attraction and Lewis acid-base attraction, resulting in the migration of coal fines. Both the values of the predictedCSCs for the migration of coal fines in propped fractures and cleats were consistent with experimental data, indicating theeffectiveness of the model. During hydraulic fracturing, the salinity of fracturing fluid can be designed between the CSCsfor the migration of coal fines in propped fractures and cleats. In that case, the production of coal fines in propped fracturesis promoted while the migration of coal fines is inhibited in cleats, so as to achieve the dual purposes of coal finescontrol in propped fractures and cleats.
  • 关键词

    煤粉运移压裂液临界矿化度支撑裂缝裂隙

  • KeyWords

    coal fines migration;fracturing fluid;critical salt concentration;propped fracture;cleat

  • 基金项目(Foundation)
    国家自然科学基金资助项目(42002182,42030810,41727801)
  • DOI
  • 引用格式
    皇凡生,桑树勋,刘世奇,等. 压裂液矿化度对支撑裂缝及裂隙内煤粉运移的影响[J]. 煤炭学报,2023,48(4):1622−1633
  • Citation
    HUANG Fansheng,SANG Shuxun,LIU Shiqi,et al. Impact of salinity of fracturing fluid on the migration of coal fines in propped fractures and cleats[J]. Journal of China Coal Society,2023,48(4):1622−1633
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