产液气井泡沫排液起泡能力分析

The foamability analysis of foam drainage in liquid-producing gas wells

起泡能力是决定产液气井泡沫排液效果的关键,但其评价依赖实验手段,缺少理论模型。针对现阶段缺乏起泡模型的环雾流及搅拌流,基于能量守恒原理,考虑界面张力对气体夹带的影响,以诱发气体夹带的液膜射流湍动能与夹带气泡的表面能增加速率相等为假设条件,建立了起泡模型,并通过实验数据进行了验证。基于起泡模型,给出了环雾流和搅拌流起泡所需界面张力的预测式,分析了不同流型的起泡能力。结果表明:在环雾流和搅拌流中,降低界面张力,韦伯数大于临界值时气体夹带发生,大气体质量流速确保充足的气体被夹带进入液膜,起泡能力强;段塞流中,降低界面张力,气体夹带速率增加,但受限于小气体质量流速,起泡能力弱;泡状流中,降低界面张力,促使气泡在泡状流顶部界面堆积形成泡沫,但小气体质量流速约束了气泡堆积速率,起泡能力弱。环雾流和搅拌流起泡能力强,适合泡沫排液,起泡所需界面张力可通过笔者建立的预测模型进行计算。

The foamability is a key factor for the foam drainage in liquid-producing gas wells;however,its evaluation relies on experimental means,lacking support from theoretical models.At present,there is still no foaming model for annular flow and churn flow.Based on the energy conservation law,considering the effect of surface tension on gas entrainment,it is assumed the turbulent kinetic energy of liquid film jet used for inducing gas entrainment is equal to the increase rate of surface energy of the entrained bubbles,so as to establish the forming model,and this model is verified by experimental data.On the basis of the established foaming model,the prediction formula is proposed for the interface tension required by the foaming of annular flow and churn flow,and the foamability of different flow patterns is also analyzed.The results show that with the decreasing of interface tension in annular flow and churn flow,gas is entrained if Weber number is larger than the critical value.The large gas mass flow rate ensures sufficient gas entrained into liquid film,presenting strong foamability.The gas entrainment rate increases with the decreasing of interface tension in slug flow.However,limited by the small gas mass flow rate,the foamability is weak.In bubble flow,bubbles are accumulated at the top interface of bubble flow with the decreasing of interface tension.However,the bubble accumulation rate is limited by the small gas flow rate,which results in weak foamability.The strong foamability exists in annular flow and churn flow,applicable to foam drainage.The interface tension required by foaming can be calculated by the prediction formula proposed in this paper.