Enhancing Production Efficiency by Unloading Produced Water and Condensate Using Engineered Surfactants: Case Histories

Abstract

Due to the depletion of reservoirs, liquid loading has become one of the common issues in mature fields. It happens where gas rates are not sufficient to lift associated reservoir fluids to the surface. Foaming surfactant injection is one of the methods used to mitigate liquid loading and enhance stable hydrocarbon production. In foam-assisted lift, a well is offloaded by creating foam downhole by the injection of surfactants. Surfactants reduce the liquid surface tension resulting in foam creation when the gas mixes with water or condensate downhole. This results in reduced liquid density and reduces hydrostatic pressure, thereby increasing drawdown and increasing resulting production. We have developed a method to design and evaluate foaming surfactant performance for unloading water and for unloading condensate. This method eliminates the potential to create stable emulsions (through high mechanical shear). Additionally, the methods outlined will avoid misleading interpretations where only the foam half-life has been considered. Falsely optimistic results, from a foam half-life perspective, can occur where certain surfactants result in "weak" foams that can maintain volume while "dropping" a large fraction of the "liquid" out of the foam. In this method, foam density, or foam mass versus time, is considered. The study results in an evaluation through the measurements of the time to create a known volume of foam, the rates of foam dissipation, and liquid phase recovery rates. This analysis is done by plotting foam multiple parameters versus time. Finally, the observation of individual phase attributes is carried out. This paper will introduce a unique methodology, process, and design to evaluate foaming surfactants for condensates and for produced water. This paper will also present the findings from foaming surfactant applications for unloading produced water in the Middle East, Asia, and unloading condensate from wells in Europe. This work will help in optimizing the design for foaming surfactants and, hence, help enhance hydrocarbon production.