An accurate prediction of the critical gas velocity for the liquid loading is of great importance for operators to select the tubing diameter for the newly drilled gas wells,or to optimize the production rate for prod...An accurate prediction of the critical gas velocity for the liquid loading is of great importance for operators to select the tubing diameter for the newly drilled gas wells,or to optimize the production rate for production wells.It is clear from previous experimental studies of the liquid entrainment rate in the gas core that the liquid is mainly carried in the form of film under the critical condition of the liquid loading onset.It is more reasonable to establish a mathematical model based on the film reversal rather than based on the droplet reversal.In our previous paper entitled“Prediction of the critical gas velocity of liquid unloading in the horizontal gas well”,a new analytical model was established based on the force balance between the gas-liquid interfacial friction force and the bottom film gravity,but the model is not very convenient to use because of the complexity of calculating the average film thickness.In the present study,a new method is proposed to calculate the average film thickness from the bubble drift velocity in the mixture,so the new analytical model becomes much easier to use.The new analytical model is evaluated against 103 sets of experimental data,the data in 124 vertical gas wells and one horizontal gas well.Meanwhile,the effect ofthe liquid loading on the production of the horizontal gas well is also analyzed.展开更多
Gas wells often encounter blockages in gas recovery channels owing to fluid accumulation during the later stages of extraction,which adversely affects subsequent recovery efforts.These undesirable conditions(e.g.,high...Gas wells often encounter blockages in gas recovery channels owing to fluid accumulation during the later stages of extraction,which adversely affects subsequent recovery efforts.These undesirable conditions(e.g.,high condensate content,high temperature,and high salinity)often affect foaming agent performance.In this study,surfactants were screened using an airflow method that closely resembles field treatment method.Notably,alcohol ether sulfates(AE_(n)S)with various polyoxyethylene(EO)units demonstrated exceptional performance in terms of liquid unloading efficiency and foam stability.At 80℃,the unloading efficiency of AE_(n)S with two EO units(AE_(2)S)in a high NaCl mass concentration(up to 200 g/L)and high condensate volume fraction(up to 20%)reached 84%.The dynamic surface tension and interfacial tension measured at the same temperature were used to analyze the influence of the diffusion rate and interfacial characteristics on the AE_(n)S foam,while the viscosity and liquid film thickness measurements reflected the mechanical strength and liquid-carrying capacity.In addition,transmission electron microscopy(TEM)revealed that AE_(2)S formed“dendritic”micellar aggregates at a high NaCl mass concentration,which significantly enhanced the viscosity and stability of the foam.The interactions among AE_(n)S,NaCl,and H2O were analyzed using molecular dynamics,and it was confirmed from a molecular mechanics perspective that a stable structure can form among the three,contributing to the foam stability.These findings demonstrate the significant potential of the AE_(2)S foam for gas well deliquification.展开更多
The inability of the gas rate to overcome the gas critical(minimum)flow rate leads to liquid loading in a gas well.To avoid premature well shut-in,the injection of surfactants is one of the standard methods used in ga...The inability of the gas rate to overcome the gas critical(minimum)flow rate leads to liquid loading in a gas well.To avoid premature well shut-in,the injection of surfactants is one of the standard methods used in gas well deliquification,although many commercial surfactants pose environmental toxicity concerns.This project investigates the suitability of biosurfactants in generating foam that will reduce the surface tension of the liquid by adsorbing at the liquid-gas interface to create a more significant mass than the liquid droplets which can be easily extracted from the walls of the wellbore.An experimental setup simulating gas well conditions introduce a surfactant derived from soybean oil,subjecting it to tests for foam stability,unloading efficiency,and dynamic surface tension.The results from the modified ASTM D-892 test show that Soybean Oil Derived Surfactant(SODS)exhibits promising surface tension reduction properties and effectively alters the gas-liquid interface.With the increase in concentration from 200 ppm,400 ppm,and 600 ppm,the expelled water increased from 17%,28%,and 70%respec-tively.Similarly,Gao-Rosen adsorption isotherms confirmed SODS appropriate for the prediction of the adsorption from solution with the R 2 values of approximately 1.0.This study introduces a cost-effective and environmentally friendly surfactant that performs favorably for gas well deliquification.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.No.51974263).
文摘An accurate prediction of the critical gas velocity for the liquid loading is of great importance for operators to select the tubing diameter for the newly drilled gas wells,or to optimize the production rate for production wells.It is clear from previous experimental studies of the liquid entrainment rate in the gas core that the liquid is mainly carried in the form of film under the critical condition of the liquid loading onset.It is more reasonable to establish a mathematical model based on the film reversal rather than based on the droplet reversal.In our previous paper entitled“Prediction of the critical gas velocity of liquid unloading in the horizontal gas well”,a new analytical model was established based on the force balance between the gas-liquid interfacial friction force and the bottom film gravity,but the model is not very convenient to use because of the complexity of calculating the average film thickness.In the present study,a new method is proposed to calculate the average film thickness from the bubble drift velocity in the mixture,so the new analytical model becomes much easier to use.The new analytical model is evaluated against 103 sets of experimental data,the data in 124 vertical gas wells and one horizontal gas well.Meanwhile,the effect ofthe liquid loading on the production of the horizontal gas well is also analyzed.
文摘Gas wells often encounter blockages in gas recovery channels owing to fluid accumulation during the later stages of extraction,which adversely affects subsequent recovery efforts.These undesirable conditions(e.g.,high condensate content,high temperature,and high salinity)often affect foaming agent performance.In this study,surfactants were screened using an airflow method that closely resembles field treatment method.Notably,alcohol ether sulfates(AE_(n)S)with various polyoxyethylene(EO)units demonstrated exceptional performance in terms of liquid unloading efficiency and foam stability.At 80℃,the unloading efficiency of AE_(n)S with two EO units(AE_(2)S)in a high NaCl mass concentration(up to 200 g/L)and high condensate volume fraction(up to 20%)reached 84%.The dynamic surface tension and interfacial tension measured at the same temperature were used to analyze the influence of the diffusion rate and interfacial characteristics on the AE_(n)S foam,while the viscosity and liquid film thickness measurements reflected the mechanical strength and liquid-carrying capacity.In addition,transmission electron microscopy(TEM)revealed that AE_(2)S formed“dendritic”micellar aggregates at a high NaCl mass concentration,which significantly enhanced the viscosity and stability of the foam.The interactions among AE_(n)S,NaCl,and H2O were analyzed using molecular dynamics,and it was confirmed from a molecular mechanics perspective that a stable structure can form among the three,contributing to the foam stability.These findings demonstrate the significant potential of the AE_(2)S foam for gas well deliquification.
文摘The inability of the gas rate to overcome the gas critical(minimum)flow rate leads to liquid loading in a gas well.To avoid premature well shut-in,the injection of surfactants is one of the standard methods used in gas well deliquification,although many commercial surfactants pose environmental toxicity concerns.This project investigates the suitability of biosurfactants in generating foam that will reduce the surface tension of the liquid by adsorbing at the liquid-gas interface to create a more significant mass than the liquid droplets which can be easily extracted from the walls of the wellbore.An experimental setup simulating gas well conditions introduce a surfactant derived from soybean oil,subjecting it to tests for foam stability,unloading efficiency,and dynamic surface tension.The results from the modified ASTM D-892 test show that Soybean Oil Derived Surfactant(SODS)exhibits promising surface tension reduction properties and effectively alters the gas-liquid interface.With the increase in concentration from 200 ppm,400 ppm,and 600 ppm,the expelled water increased from 17%,28%,and 70%respec-tively.Similarly,Gao-Rosen adsorption isotherms confirmed SODS appropriate for the prediction of the adsorption from solution with the R 2 values of approximately 1.0.This study introduces a cost-effective and environmentally friendly surfactant that performs favorably for gas well deliquification.
