Abstract
Gas wells producing late in their life are normally subject to liquid loading problems. As rates fall below the critical rate necessary for unloading, a static liquid column will often develop in the well. This can result from condensed water out of the gas phase or formation water being produced into a well having insufficient gas velocity to clear the liquid from the wellbore. The presence of this liquid column impairs the well performance by imparting additional back pressure on the reservoir. The water saturation around the wellbore can increase causing a reduction in the near well effective gas permeability which further compounds the problem of keeping the well unloaded. Traditional methods of evaluating well performance do not properly capture this phenomena; therefore, the existence of additional back pressure on the reservoir can go undetected. Wells continue to produce, but at a reduced rate because of the liquid column. Numerous analysis techniques are available to model static liquid columns in wellbores. A review of these methods and an evaluation of these techniques is presented. Comparisons with field data are made to ascertain the accuracy of the methods and to select an appropriate method to model well performance. Incorporation of this method into a well design allows for the optimization of well productivity.
