气井稳定携液之我见

业内对于临界携液流量的认识一直都存在着分歧。以Turner、李闽为代表的液滴携液理论观点认为"当气体流速达到一定数值后,液相分散成小液滴被携带走";而以李颖川等为代表的气液两相管流实验模拟者则认为"在气井生产过程中雾状流很难出现,气井生产基本上是以段塞流为主,液滴模型无法解释气井实际排液情况"。为了还原低压低产气井实际生产状态,基于弗劳德相似准数,以流速相似原理模拟低压、低产井实际生产情况,并开展了相应的实验研究。结果表明:①低压、低产气井实际上存在"上雾+下段塞"混合流动状态;②上部雾状流携液满足液滴模型计算结果,当气相流速高于临界携液流速则上部可连续带液,否则会导致积液段液量缓慢增加;③下部表现为段塞流,当气相流速高于1.95 m/s,则表现为连续流动,气井基本无积液,当气相流速低于0.195 m/s,则表现为难以流动,气井不产液,面临水淹。实验所得结果与气井实际生产情况相当吻合,可以为气井有效开采提供技术支撑。

Stable fluid-carrying capacity of gas wells

There are intensive disputes over critical fluid-carrying capacity among people in the industry. According to the principles of droplet fluid-carrying proposed by Turner and Li Min, "liquids may be dispersed into droplets and carried away when flow rates of gases reached a certain level". Some scholars, such as Li Yingchuan, proposed different opinions after simulation tests involving gas and liquid flows, and they believed that "It is very difficult to generate mist flow during the production in gas wells, which are dominated by slug flow. Accordingly, the droplet model may not be used to interpret the actual fluid-discharging performances in gas wells". To simulate the actual production conditions in low-pressure and low-productivity wells accurately, Froude number was used to simulate the actual performances of such wells by using the principle of similarity in flow rates. In addition, corresponding lab tests were conducted. Research results show that the low-pressure and low-productivity wells are actually dominated by mixed flow characterized by mists in upper sections and slugs in lower sections. Mist flow in upper sections may have fluid-carrying capacities conforming to the calculation results by the droplet model. As long as the flow rates of gases are higher than the flow rate corresponding with critical fluid-carrying capacity, constant fluid-carrying capacities can be obtained in upper sections; otherwise, volumes of fluids in accumulation sections may increase slowly and continuously. Moreover, lower sections are dominated by slug flow. With flow rates of gases higher than 1.95 m/s, lower sections are dominated by continuous flow with basically no accumulation of fluids. When flow rates of gases are lower than 0.195 m/s, these sections can hardly sustain any flow. With no fluid production, these gas wells may be flooded. These lab test results coincided well with the actual production performances of gas wells, providing reliable technical supports for highly- efficient development of gas wells.