微泡沫与普通泡沫注入性及调剖能力对比

针对普通泡沫注入性差、运移性弱的问题,将气体和起泡剂溶液同时注入填砂管发泡器制备出一种气泡微细的微泡沫体系。通过多测压点长填砂管和并联填砂管对比了微泡沫和普通泡沫注入性和调剖能力的差异,并借助微观非均质模型对比研究了微泡沫和普通泡沫的封堵机制及改善微观非均质能力。微观驱替实验表明,由于微泡沫气泡直径小于高渗区域孔喉直径,气泡受孔喉的约束较小,主要通过多个气泡叠加作用在高渗区域孔喉处形成堆积封堵,后续气泡以"直接通过"或"弹性变形"的方式流入低渗区域,少量气泡以"气泡陷入"方式封堵小孔喉,但高渗区域堆积的微泡沫易被冲散,导致其封堵强度较弱,调剖作用有限。与微泡沫相比,普通泡沫的平均气泡直径大于高渗孔喉直径,气泡通过孔喉时的流动阻力较大,封堵能力较强,气泡主要通过"弹性变形"和"液膜分异"作用进入孔喉。相同泡沫注入量条件下,普通泡沫微观调剖效果更好。微泡沫在填砂管沿程产生的压差分布较为均匀,其注入性和深部封堵能力优于普通泡沫,但其封堵高渗通道能力及耐水冲洗能力较弱,调剖能力弱于普通泡沫。

Comparison of injectivity and profile control capacity of microfoam and common foam

Aiming at the problems of poor injectivity and worse migration of common foam, microfoam with tiny diameter is prepared by co-flowing gas and foaming agent to sand pack pipe foaming generator. The differences of injectivity and profile control of microfoam and common foam were compared by testing multiple pressure of long sand pack and parallel sand packs. Plugging mechanism and effectiveness in improving profile control capacity of microfoam and common foam were evaluated by micromodel tests. The results show that bubble diameter of microfoam is less than the pore throat diameter of high permeability area, the flow resistance of bubble is lower. Microfoam would block pore throat of high permeability area through the way of bubble accumulation, subsequent bubbles would flow into low permeability area with the way of directly through or elastic deformation, and a small number of bubbles could block small pore throat through the way of bubble trapped. However, the microfoam accumulated in the high permeability area is easily dispersed, resulting in a weak blocking strength and limited profile control ability. Compared with microfoam, bubble diameter of common foam is more than the pore throat diameter in high permeability area, flow resistance is greater and plugging ability is stronger, the bubbles mainly flew through the way of elastic deformation and liquid membrane differentiation into the pore throat. Profile control capacity of common foam is better at the same foam injected volume. Microfoam could produce more uniform differential pressure across the sand pack, and its injectivity and deep plugging ability are better than the common foam, but the capacity of blocking high permeability channel, water flushing resistance, and profile control is weaker.