Research On Gas-liquid Transport Model In Inclined Gas Wells

Described as flow reversal and liquid accumulation in the wellbore,the loading phenomenon is a severe problem for gas wells,as it reduces the production rate and,in some critical instances,stops the production,resulting in significant economic losses.Therefore,accurate prediction and identification of the loading point are essentials for the operating company to anticipate all kinds of economic losses.A thorough analysis of available studies and the results they obtained show that it is more rational to attribute the loading phenomenon to film reverse flow.This thesis endorses the film flow reversal theory to develop a model that predicts and identifies the loading phenomenon in vertical and inclined gas wells.The thesis modifies the model proposed by Barnea^[1],and combines it with the gas and liquid phases Hagen-Poiseuille equations and the circumferential angle model developed by Luo et al.^[2],while considering gas-liquid amount variation,and based on the assumption that the loading phenomenon occurs when the film starts to flow in a direction that is counter-current to the gas.As a result,the model obtained considers the effects of gas-liquid amount variation,the tubing diameter,the inclination angle,and the circumferential angle of the well.It also considers the current rate of flowing gas,the pressure gradient,and the effects of the variation on the well and fluid properties.An evaluation of the energy transferred by the moving gas and liquids in the annular regime configuration is conducted over the entire length of the tubing.Thus,the mechanical energy balance equation is implemented to compute the energy transferred by the fluids.The tubing is therefore divided into several tubing segments,and the energy transferred in each tubing segment is evaluated.After that,a detailed computation of the energy transmitted over the entire length of the tubing is carried out.The introduction of fluid conditions at the beginning of the loading phenomenon coupled with the implementation of the developed expression of the pressure drop at the onset of loading equation allows the assessment of the energy balance at the beginning of liquid loading.Consequently,from this energy assessment at the initiation of liquid reversal,a correlation that defines where the fluid reversal occurs is developed,and the corresponding pressure drop at that point could be evaluated.A published gas field data set and a newly acquired gas field data set are used to authenticate the developed models.As a result,the predictions obtained for vertical wells are 95%,90%,and 94%,with a precision of 23.6%,respectively,for the Northwest Xinjiang gas field data set,the Turner et al.^[3]data set and the Coleman et al.^[4]data set.As for inclined gas wells,the predictions obtained are 92%and 90%,with a precision of 13%,respectively,for Gao^[5]data set and the Veeken et al.^[6]data set.Subsequently,the new model outperformed the models developed by Turner et al.^[3],Li et al.^[7],Belfroid et al.^[8],Chen et al.^[9]and Liu et al.^[10].Consequently,the loading phenomenon is more compatible with the film flow reversal theory rather than it is with the liquid drop reversal flow theory.Moreover,the new model is more suitable to forecast and identify the loading phenomenon in both low-pressure and high-pressure inclined and vertical gas wells.A determination of the loading location shows that as the critical velocity increases,the loading phenomenon occurs deeper in the well.