Screening Artificial Lift and Other Techniques for Liquid Unloading in Unconventional Gas Wells

Abstract

Abstract Unconventional gas reservoirs are characterized by steep declines in reservoir pressure as production progresses. This results in frequent liquid loading problems, thereby reducing gas production to zero. To resume production, a means of unloading the liquid is required. This paper presents a review of artificial lift methods and other techniques that can be employed to unload liquids from these wells. A ranking is also presented 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 casing size. A total of 19 artificial lift methods and other techniques capable of unloading liquids in high gas content 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 wet gas compression. Subsequently, a ranking of the different methods was performed. The ranking constraints included 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 in unconventional gas wells. This highest ranked group was followed closely by the positive displacement artificial lift methods, such as sucker rod pumps and long-stroke rod pump methods. The method with the lowest 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 specific method finally selected by the application engineer will depend on existing infrastructure and the economics of adding existing equipment to implement the system. This study highlights the results from screening artificial lift methods and other techniques for use in unloading liquids from an unconventional gas well. It brings together these different unloading methods in one paper and serves as a guide for field engineers to assess operational suitability for their unconventional gas wells. Such knowledge serves as a worthwhile first step toward planning and implementation of a means to unload liquids in a target unconventional gas well.