(75a) Experimental Characterization of Surfactant Application in Gas Wells and in Presence of Water and Condensates

Liquid loading or inability of gas to carry the accumulated liquids along the wellbore, shortens the life of Natural Gas Wells, costing the operators in revenue. One of the common gas-well deliquification techniques is surfactant (foamer) injection or foam lift. This method is proven very beneficial especially for low-pressure gas reserves, where the required critical gas velocity to avoid liquid loading is reduced to around 20% of its original value. It is known that the presence of condensed hydrocarbons lowers the surfactant’s efficiency in foam lift operations. However, hardly any studies in the literature are focused on the influence of condensates and resolving the liquid loading based on the surfactant type and formulation. This study is intended to experimentally evaluate the performances of various surfactants in the presence of both water and condensates in gas wells, with regards to unloading the liquids.

The study includes laboratory experiments, which are carried out with various surfactant types, changing surfactant concentrations, water/condensate volumetric fractions, and gas injection rates. Initially, all of the tested surfactants are characterized by static and dynamic surface tension measurements. Foam lift assessment is then completed using a state-of-art ‘Liquid Unloading Column’ that serves as a replica for a gas well. Foam lift efficiency is determined by measuring the foam density, foam half-life, and unloaded liquid. The experiments are conducted at atmospheric conditions, and the visual observations are also recorded to better evaluate the changes in multiphase flow phenomena.

The outcome of this work sheds lights on the performance of a given surfactant type and composition in the presence of varying amounts of condensates. The findings of the research are intended to contribute as an operational guideline for the selection of surfactants/formulations to unload gas wells with varying water cuts.