氮气泡沫体系稳定性的影响因素研究

Study on influence factors for stability of nitrogen foam system

利用填砂管研究了不同注气压差下多孔介质中泡沫的产生及其对气体阻力特性的影响,并对泡沫在烧杯及多孔介质中的稳定性进行了对比评价。结果表明,随着氮气注入压差的增加,泡沫对气体的初始残余阻力系数呈幂指数增加;而其残余阻力系数(对气和液)随时间均呈幂指数下降。泡沫在体相中的稳定性远低于多孔介质,且随着环境压力的增大,泡沫的稳定性呈线性增大。基于简单的孔隙模型分析可知,孔隙介质中良好的分散条件及在分散过程中具有的较厚液膜是其稳定性远远高于体相中的重要原因。孔隙和喉道半径比值越大,则孔隙中的气体附加压力越大,泡沫的初始残余阻力系数将越大;吼道越长,泡沫聚并的几率降低,其稳定性增大。若孔隙网络中非均质性越强,则孔隙中气体压差越大,不同孔隙中气体聚并的几率增大,泡沫的稳定变差。

The gas-resistance characteristics of nitrogen foam produced in sand pack was studied at different gas injection pressure. The stability evaluation of foam in beaker and porous medium indicated that the initial residual resistance factor of foam to gas in- creased in power exponent with the increment of gas injection pressure. The residual resistance factor of foam to gas and water de- creased in power exponent with equilibrium time. The stability of foam in beaker was greatly lower than that in the porous medium and increased linearly with the enhancement of environment pressure. The analysis on a simple pore model showed that good disper- sion conditions and thicker membrane in the porous medium could be the main causes for above phenomena. The initial resistance fac- tor of foam increased with the pore-throat ratio, and coalesce probability declined with the rising of throat length, which thus im- proved the stability of foam. The greater the heterogeneity of reservoir in pore scale network, the larger the gas pressure difference in pores. When the coalesce probability of gas enhancement gets bigger, the stability of foam will get worse.