Pore structure of porous media, including pore size and topology, is rather complex. In immiscible twophase displacement process, the capillary force affected by pore size dominates the two-phase flow in the porous me...Pore structure of porous media, including pore size and topology, is rather complex. In immiscible twophase displacement process, the capillary force affected by pore size dominates the two-phase flow in the porous media, affecting displacement results. Direct observation of the flow patterns in the porous media is difficult, and therefore knowledge about the two-phase displacement flow is insufficient. In this paper, a two-dimensional(2D) pore structure was extracted from a sandstone sample, and the flow process that CO_2 displaces resident brine in the extracted pore structure was simulated using the Navier eStokes equation combined with the conservative level set method. The simulation results reveal that the pore throat is a crucial factor for determining CO_2 displacement process in the porous media. The two-phase meniscuses in each pore throat were in a self-adjusting process. In the displacement process,CO_2 preferentially broke through the maximum pore throat. Before breaking through the maximum pore throat, the pressure of CO_2 continually increased, and the curvature and position of two-phase interfaces in the other pore throats adjusted accordingly. Once the maximum pore throat was broken through by the CO_2, the capillary force in the other pore throats released accordingly; subsequently, the interfaces withdrew under the effect of capillary fore, preparing for breaking through the next pore throat.Therefore, the two-phase displacement in CO_2 injection is accompanied by the breaking through and adjusting of the two-phase interfaces.展开更多
作为页岩油藏开发的一种关键技术手段,压裂阶段的动态渗吸驱油在近年来已成为油藏工程研究的热点。鉴于全球能源需求以及对非常规油气资源的持续勘探,这项技术在提高页岩油藏开采效率方面的重要性不容小觑。然而,页岩油储层动态渗吸过程...作为页岩油藏开发的一种关键技术手段,压裂阶段的动态渗吸驱油在近年来已成为油藏工程研究的热点。鉴于全球能源需求以及对非常规油气资源的持续勘探,这项技术在提高页岩油藏开采效率方面的重要性不容小觑。然而,页岩油储层动态渗吸过程中,不同因素在动态渗吸各个阶段的具体作用机制尚不明确,各因素对渗吸驱油效果的影响难以精确量化,严重制约了页岩油藏开发效率的进一步提高,导致开发成本上升,同时给资源的可持续开发带来了挑战。针对页岩油储层动态渗吸机理及作用规律不清的问题,建立了岩心尺度数值模拟模型,采用控制变量法设置了15个模拟方案,揭示了驱替压差、毛细管半径、润湿角、油水粘度对动态渗吸驱油效果的作用机制,明确了流体渗流变化规律。研究表明:动态渗吸中,毛细管半径从0.1μm增大至10μm,毛细管力减小,流体渗吸速率加快,渗吸采收率提高了8.0%;驱替压差从0 MPa开始增大,渗吸由静态升级为动态,3 MPa时渗吸采出程度提高了7.9%;认为驱替压差与采出程度符合幂函数关系,存在最优驱替压差。岩心润湿性由亲水向中性、亲油变化,采出程度由水润湿的48.9%下降到油润湿的33.9%;原油粘度由53.30 m Pa·s降低至13.99 m Pa·s,渗吸采收率提高了9.1%;驱替相粘度越大,初始渗吸速度越小,但渗吸驱油效果越好。现场操作中可通过优化注入压力,选择合适的压裂液、表面活性剂等,提高亲水程度和驱替相粘度,改善动态渗吸过程,从而增大驱油效率。未来应进一步考虑多相流动的复杂性,同时结合储层的非均质性,从不同尺度研究各因素对页岩动态渗吸过程的影响。展开更多
基金funded by Key Laboratory of Coal-based CO_2 Capture and Geological Storage,Jiangsu Province,ChinaUS Advanced Coal Technology Consortium(No.2013 DFB60140-08)
文摘Pore structure of porous media, including pore size and topology, is rather complex. In immiscible twophase displacement process, the capillary force affected by pore size dominates the two-phase flow in the porous media, affecting displacement results. Direct observation of the flow patterns in the porous media is difficult, and therefore knowledge about the two-phase displacement flow is insufficient. In this paper, a two-dimensional(2D) pore structure was extracted from a sandstone sample, and the flow process that CO_2 displaces resident brine in the extracted pore structure was simulated using the Navier eStokes equation combined with the conservative level set method. The simulation results reveal that the pore throat is a crucial factor for determining CO_2 displacement process in the porous media. The two-phase meniscuses in each pore throat were in a self-adjusting process. In the displacement process,CO_2 preferentially broke through the maximum pore throat. Before breaking through the maximum pore throat, the pressure of CO_2 continually increased, and the curvature and position of two-phase interfaces in the other pore throats adjusted accordingly. Once the maximum pore throat was broken through by the CO_2, the capillary force in the other pore throats released accordingly; subsequently, the interfaces withdrew under the effect of capillary fore, preparing for breaking through the next pore throat.Therefore, the two-phase displacement in CO_2 injection is accompanied by the breaking through and adjusting of the two-phase interfaces.
文摘作为页岩油藏开发的一种关键技术手段,压裂阶段的动态渗吸驱油在近年来已成为油藏工程研究的热点。鉴于全球能源需求以及对非常规油气资源的持续勘探,这项技术在提高页岩油藏开采效率方面的重要性不容小觑。然而,页岩油储层动态渗吸过程中,不同因素在动态渗吸各个阶段的具体作用机制尚不明确,各因素对渗吸驱油效果的影响难以精确量化,严重制约了页岩油藏开发效率的进一步提高,导致开发成本上升,同时给资源的可持续开发带来了挑战。针对页岩油储层动态渗吸机理及作用规律不清的问题,建立了岩心尺度数值模拟模型,采用控制变量法设置了15个模拟方案,揭示了驱替压差、毛细管半径、润湿角、油水粘度对动态渗吸驱油效果的作用机制,明确了流体渗流变化规律。研究表明:动态渗吸中,毛细管半径从0.1μm增大至10μm,毛细管力减小,流体渗吸速率加快,渗吸采收率提高了8.0%;驱替压差从0 MPa开始增大,渗吸由静态升级为动态,3 MPa时渗吸采出程度提高了7.9%;认为驱替压差与采出程度符合幂函数关系,存在最优驱替压差。岩心润湿性由亲水向中性、亲油变化,采出程度由水润湿的48.9%下降到油润湿的33.9%;原油粘度由53.30 m Pa·s降低至13.99 m Pa·s,渗吸采收率提高了9.1%;驱替相粘度越大,初始渗吸速度越小,但渗吸驱油效果越好。现场操作中可通过优化注入压力,选择合适的压裂液、表面活性剂等,提高亲水程度和驱替相粘度,改善动态渗吸过程,从而增大驱油效率。未来应进一步考虑多相流动的复杂性,同时结合储层的非均质性,从不同尺度研究各因素对页岩动态渗吸过程的影响。
基金"十三五"国家科技重大专项"海上油田化学驱油技术"(2016ZX05025-003)中海油_NEXEN联合研发项目"Collaborative Research to Develop and Test Activators to Improve Recovery in Tight Oil Assets"(2017OT-JY52)
