Models Of Liquid Unloading In Gas Wells

Gas produced from reservoir well,in many cases,have liquid phase material with it,the presence of which can accumulate in the wellbore over time when transporting energy is low enough in the low-pressure reservoir.The liquids accumulated in the wellbore will cause additional hydrostatic pressure on reservoir,which results in continued reduction of available transportation energy and affecting the production capacity.In some cases,it even causes gas wells to die.Thus,if we want to unload the liquid column,we have to use the process of gas production by water drainage.However,before the operation,we must decide which gas wells will be loaded by liquid.Then,there is a criterion for predicting liquid loading and choosing wells,the parameter is named critical flow rate.The critical flow rate is the minimum gas flow rate for the continuous removal of liquids from gas wells.There are many critical flow rate models for gas well.The Turner,Coleman,and Li Min models are widely used in gas fields.However,they still have some limitations;for example,these models ignore the different distribution of the critical flow rate along the entire wellbore.In this paper,the mechanism and equation of four critical flow rate models are compared,the affecting factors of critical flow rate are analyzed by calculation,and,using the data from Turner’s paper and the production data of gas wells from the Changqing gas field,the critical flow rates are calculated.The obtained results and the conclusions of the research are:Firstly,the critical flow rate of liquid unloading increase with the pipe diameter,the pressure,the temperature,effected by surface tension,and the distribution of the critical flow rate along the wellbore is closely related with temperature and pressure conditions at various depths.For gas well with low WGR,the critical flow rate decrease with depth firstly,then increase with depth,the critical flow rate at the middle and lower position of well is minimum;for gas well with great WGR,the critical flow rate increase with depth,the critical flow rate at the well head is minimum.Secondly,the Turner and Coleman model provides a reasonably good fit for the production or liquid loading status of gas well from the Third gas production plant,Changqing gas field;Thirdly,all kinds of critical liquid-carrying models are simple,but their physical principles are clear and reasonable,the most important thing is that ensuring the input parameters are accurate.The findings of this study are applicable to the technology optimization and enhance gas recovery for gas well producing water.