基于能量守恒定律的气井井筒携液工况诊断模型

A new wellbore fluid load diagnosing model based on the energy conservation law

井筒积液的产生对气井稳产有着较大的不利影响,而现有的井筒积液诊断方法又存在着应用局限性。为了明确产液量较大时气井井筒中两相流的携液机理、准确诊断井筒积液存在情况、合理制订气井生产措施,在前期研究的基础上,基于能量守恒定律,建立了气液两相垂管流的携液工况诊断新模型,通过与现场实践统计、室内实验数据进行比较,对新模型的准确性进行了验证,并采用新模型对某产液气井的携液工况进行了分析。研究结果表明:①产液量较少时,新模型计算得到的临界携液气量明显低于Turner模型的计算结果;②随着产液量增大,采用新模型计算得到的临界携液气量逐渐增大,并且压力越高,临界携液气量增大越明显;③气液两相垂管流的流型可分为气泡流、段塞流、过渡流、波浪流和环雾流5种,当两相流型为过渡流、波浪流或环雾流时,井筒中不存在积液。结论认为,新模型计算结果与现场实践统计、室内实验结果基本一致,诊断结论符合实际,具有普适性,可以为产液气井的携液工况诊断和积液预防提供理论支撑。

Liquid load has huge adverse effects on the borehole stability of a gas well.However,the existing liquid load detection techniques are somewhat limited in practical application.For the purpose of clarifying the liquid-carrying mechanism of two-phase flow in the wellbore with a higher liquid production rate,it is necessary to accurately diagnose the presence of liquid loading in the wellbore and reasonably formulate the production measures of the gas well.On the basis of previous studies,this paper established a new model for diagnosing the liquid-carrying conditions of gas-liquid two-phase vertical pipe flow according to the law of energy conservation.Then,by comparing with field practice statistics and indoor experimental data,the accuracy of the new model was verified.Finally,the new model was applied to analyze the liquid-carrying condition of one certain liquid-producing gas well.And the following research results were obtained.First,when the liquid production rate is lower,the critical liquid-carrying gas rate calculated by the new model is much lower than the calculation result of the Turner model.Second,with the increase of the liquid production rate,the critical liquid-carrying gas rate calculated by the new model increases gradually.And the higher the pressure is,the more obvious the increase of the critical liquid-carrying gas rate is.Third,from the perspective of flow pattern,the gas-liquid two-phase vertical pipe flow can be divided into 5 kinds,including bubble flow,slug flow,transition flow,wave flow and annular mist flow.When the two-phase flow is transition flow,wave flow or annular mist flow,there is no liquid loading in the wellbore.In conclusion,the calculation result of the new model is basically accordant with field practice statistics and indoor experimental data,and its diagnostic conclusion conforms to the actual situations.Obviously,this model is of universality and provides a theoretical support for the diagnosis of liquid-carrying condition and the prevention of fluid loading in liquid-producing gas wells.