FOAM LIFT EFFICIENCY FOR GAS WELL DELIQUIFICATION IN PRESENCE OF CONDENDATES

Abstract

Over the life of Natural Gas wells, as the formation pressure declines, they face the issue of liquid loading. Liquid loading or inability of gas to carry the accumulated liquids along the wellbore shortens the life of gas wells, costing the operators in revenue. One of the common gas-well deliquification techniques is surfactant injection or foam lift. This method is proven very beneficial especially at low-pressure gas reserves, where the required critical gas velocity to avoid liquid loading gets reduced to around 20% of its original value. However, it is known that the presence of condensed hydrocarbons lowers the surfactant’s efficiency in foam lift operations. In this study experimental evaluation of the performances of various surfactants in presence of both water and hydrocarbon condensates with regards to unloading the liquids is carried out. Experimental work includes characterization of surfactants based on static and dynamic surface tension measurements and liquid unloading tests with varying surfactants and concentrations, changing liquid column water cuts and a fixed Nitrogen gas injection rate to generate foam at room temperature and at high temperature. The results are recorded in terms of unloaded liquid, liquid drainage rate, foam quality, foam density, and foam half-life. A noticeable drop is observed in liquid unloading as the water cut is reduced showing the diminishing foam lift efficiency at room temperature and at high temperature as well. However, the significance of this drop is different for different surfactant types.