韦世明,金衍,夏阳,徐丹,曾萍. 自发渗吸对页岩油储层压裂后闷井的影响[J]. 石油钻采工艺,2023,45(6):756-765. DOI: 10.13639/j.odpt.202302025
引用本文: 韦世明,金衍,夏阳,徐丹,曾萍. 自发渗吸对页岩油储层压裂后闷井的影响[J]. 石油钻采工艺,2023,45(6):756-765. DOI: 10.13639/j.odpt.202302025
WEI Shiming, JIN Yan, XIA Yang, XU Dan, ZENG Ping. Influence of spontaneous imbibition on post-fracturing well soaking in shale oil reservoirs[J]. Oil Drilling & Production Technology, 2023, 45(6): 756-765. DOI: 10.13639/j.odpt.202302025
Citation: WEI Shiming, JIN Yan, XIA Yang, XU Dan, ZENG Ping. Influence of spontaneous imbibition on post-fracturing well soaking in shale oil reservoirs[J]. Oil Drilling & Production Technology, 2023, 45(6): 756-765. DOI: 10.13639/j.odpt.202302025

自发渗吸对页岩油储层压裂后闷井的影响

Influence of spontaneous imbibition on post-fracturing well soaking in shale oil reservoirs

  • 摘要: 针对目前页岩油储层压裂后是否闷井、闷井时间设计缺乏理论指导的难题,建立了考虑毛细管渗吸的油水两相渗流模型,并采用有限元-有限体积方法进行闷井和生产联合模拟,模拟过程考虑了页岩基质渗吸是否产生微裂缝对渗吸和生产的影响,研究了闷井时间和毛管力对闷井过程中页岩基质吸水量和开井后页岩油产量的影响。分析模拟结果发现:若页岩基质渗吸压裂液后产生微裂缝,渗吸作用能够明显提高页岩油产量;随着闷井时间和页岩亲水性增加,页岩基质渗吸压裂液后产生更多微裂缝,且水油置换作用更强,页岩油产量也随之增加。若页岩基质渗吸压裂液不产生微裂缝,渗吸作用将降低页岩油产量;随着闷井时间和页岩亲水性增加,基质中的含水饱和度增加,油相相对渗透率降低,页岩油产量随之降低。该研究成果明确了并非所有页岩油储层均适合压裂后闷井,对页岩油储层压裂设计具有重要指导意义。

     

    Abstract: To address the current challenges such as the determination of well soaking after fracturing in shale oil reservoirs and lack of theoretical guidance on the design of soaking duration, this study established an oil-water two-phase flow model in consideration of capillary imbibition. By employing finite element-finite volume methods, joint simulation of well soaking and production was performed, which took into account whether the imbibition of the shale matrix will produce micro-fractures and their influence on imbibition and production. Furthermore, the influences of well soaking duration and capillary force on the water absorption of shale matrix during well soaking process and the shale oil production after well opening were investigated. The simulation results revealed that if micro-fractures are generated in the shale matrix due to capillary imbibition of fracturing fluid, imbibition significantly enhances shale oil production. With increasing well soaking duration and shale hydrophilicity, more micro-fractures will be generated in the shale matrix after fracturing, and the water-oil displacement effect becomes stronger, leading to increased shale oil production. In cases where capillary imbibition does not introduce micro-fractures in the shale matrix, the imbibition effect will reduce shale oil production. With soaking duration and shale hydrophilicity increase, water saturation in the matrix rises, causing a decrease in the relative permeability of the oil phase, resulting in reduced shale oil production. This study clarifies that not all shale oil reservoirs are suitable for well soaking after hydraulic fracturing, which provide a crucial guidance for the design of hydraulic fracturing in shale oil reservoirs.

     

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