Screening Artificial Lift and Other Techniques for Liquid Unloading inUnconventional Gas Wells

摘要

Unconventional gas reservoirs are characterized by steep declines in reservoir pressure as productionprogresses.This results in frequent liquid loading problems,thereby reducing gas production to zero.Toresume production,a means of unloading the liquid is required.This paper presents a review of artificial liftmethods and other techniques that can be employed to unload liquids from these wells.A ranking is alsopresented to highlight the most preferred system for a target well.A detailed review of liquid loading was performed for an unconventional gas well with 5.5-inch casingsize.A total of 19 artificial lift methods and other techniques capable of unloading liquids in high gascontent flows were investigated.These included gas lift(continuous,plunger-assisted,gas-assisted,etc.),positive displacement pumps(progressing cavity,sucker rod pump,etc.),electric submersible pumps(ESPs),jet pump,and other techniques such as supersonic nozzles,wellbore heating and downhole wetgas compression.Subsequently,a ranking of the different methods was performed.The ranking constraintsincluded setting depth,operating temperature,production rate,gas handling limitation,and economics.The results indicate that the gas lift related artificial lift methods(continuous,plunger-assisted,gas-assisted),plunger/dual stage plunger lift systems,ranked highest as a suitable means to unload liquids inunconventional gas wells.This highest ranked group was followed closely by the positive displacementartificial lift methods,such as sucker rod pumps and long-stroke rod pump methods.The method with thelowest ranking was the linear ESP.The other techniques with mid-ranking showed promising applicability,which may likely become viable in the future.For methods within the highest ranked bracket,the specificmethod finally selected by the application engineer will depend on existing infrastructure and the economicsof adding existing equipment to implement the system.This study highlights the results from screening artificial lift methods and other techniques for use inunloading liquids from an unconventional gas well.It brings together these different unloading methods inone paper and serves as a guide for field engineers to assess operational suitability for their unconventionalgas wells.Such knowledge serves as a worthwhile first step toward planning and implementation of a meansto unload liquids in a target unconventional gas well.