微泡沫直径与地层孔隙直径的匹配关系

将气液两相流通过填砂管制备一种气泡直径主要分布于10～100 μm的微泡沫,通过微观实验研究气液比和填砂管渗透率对微泡沫直径的影响,揭示微泡沫封堵机制。采用多测压点人造岩心模拟多孔介质研究微泡沫对地层起封堵作用时微泡沫直径与地层孔隙直径的匹配关系。结果表明:通过调节气液比、填砂管渗透率可实现微泡沫平均气泡直径12.39～99.31 μm可调;当微泡沫平均气泡直径与岩心平均孔隙直径比为1.45～2.16时,微泡沫兼具较好的注入性及深部封堵能力,此时微泡沫直径与岩心孔隙直径相匹配,通过调节微泡沫平均气泡直径,可使微泡沫与渗透率为0.02～10.9 μm2的地层匹配;微泡沫主要通过气泡叠加作用在高渗区域形成暂堵带,后续流动的微泡沫以“弹性变形”或“直接通过”的方式流入低渗区域,少量气泡以“纹理状”结构占据小孔隙处形成封堵;随着气液比增加,微泡沫气泡数量增加,在孔隙处由间歇性的封堵方式向持续的封堵方式转变,微泡沫封堵能力和可变形性增强,气液比为1时的封堵能力最强。
In order to further understand the matching relationship between microfoam diameter and formation pore diameter, one microfoam with bubble diameter distribution from 10 to 100 μm was fabricated by gas/fluid flow through sandpack, through which the effect of gas liquid ratio and sandpack permeability on microfoam diameter were investigated, and the plugging mechanism of microfoam were revealed by micromodel tests. The displacement experiments were conducted using artificial core with multiple pressure points to simulate porous media, and the matching relationship between microfoam diameter and formation pore diameter was studied when microfoam plugged formation was established. The results show that average bubble diameter of microfoam could be controlled from 12.39 to 99.31 μm by changing gas liquid ratio and sandpack permeability. When the ratio of microfoam average bubble diameter to core average pore diameter is 1.45-2.16, microfoam shows both good better injectivity and deep plugging capacity, which considers the microfoam diameter matches with core pore diameter at the moment. The microfoam could be matched with permeability from 0.02 to 10.9 μm2 by adjusting the average bubble diameter of microfoam. The microfoam would create a temporary blocking zone in high permeable region through bubble accumulation, and the subsequent microfoam would flow through the low permeable region directly or by means of elastic deformation. A small amount of finely textured microfoam with smaller bubbles could occupy pore to form plugging. As the increase of gas liquid ratio, the bubble quantity of microfoam increases, and the blocking mode of microfoam at pore changes from intermittent plugging to continuous plugging, which leads to the enhancement of plugging capacity and deformability of microfoam. The strongest plugging capacity is reached when the gas liquid ratio is 1