储气库碳酸盐岩裂隙微粒运移实验模拟

Physical Simulation of Carbonate Particle Migration in Gas Storage

储气库井在注采过程中因注采压力过大可能诱发微粒运移,为此,选用储气库碳酸盐岩储层岩心制取人工裂缝岩心,分别开展了应力敏感实验、干燥岩心和含水岩心气体速敏实验、模拟储气库注采压力增加时干燥岩心和含水岩心的流动实验,测试了实验过程中岩心渗透率,并借助扫描电镜对模拟储气库注采压力增加时和应力敏感实验前后岩心的裂缝壁面进行检测,揭示储气库注采过程中微粒运移机理。实验表明:干燥岩心和含水岩心的速敏程度分别为中等偏弱—中等偏强和中等偏强—强,岩心应力敏感程度为弱—中等偏弱;模拟储气库注采压力增加时干燥岩心和含水岩心的平均渗透率损害率分别为77%和84%。研究认为,注采过程中的裂缝壁面的微粒在高速气流拖拽作用下发生拉张破坏和有效应力下岩石被破坏是微粒运移的重要诱发机制,含水情况下岩石强度弱化,会强化微粒运移。建议合理控制注采压力和减少流体进入储气库井,防止产生大量微粒,最终影响储气库的多尺度注采,同时对于合理控制储气库的注采压力具有借鉴意义。

Particle migration may be induced due to the excessive pressure during injection and production process in gas storage well.Carbonate reservoir core samples in gas storage were taken to prepare samples with artificial fractures.Stress sensitivity test and velocity sensitivity tests of dry and water-bearing samples were conducted to simulate the fluid flow in dry and water-bearing samples under an increase of gas storage injection production pressure,and the corresponding sample permeabilities were measured during the experiment.Scanning electron microscopy was used to detect the fracture surface before and after stress sensitivity experiment to reveal the particle migration mechanism of gas storage injection-production process.Experiment indicates that the velocity sensitivitiy of dry and water-bearing core samples are medium-weak to medium-strong and medium-strong to strong respectively.The corresponding stress sensitivity is weak to medium-weak.The average permeability loss ratios of dry and water-bearing core samples are 77% and 84% for the particle migration simulation with a increase of gas storage injection-production pressure.Research indicates that the major particle migration mechanisms include the tensile failure of particle on the fracture surface results from high velocity gas flow dragging and rock damage under effective stress in the injection-production process.The rock strength decreases under water condition,which will intensify particle migration.It is recommended to restrict injection-production pressure and reduce fluid flow into gas storage well to prevent the generation of particles an enhance the multi-scale injection-production efficiency of gas storage.This research could provide certain reference for the reasonable injection-production pressure maintenance.