Mitigation of the Effects of Condensate Banking: A Critical Review

Abstract

Summary With production from gas/condensate reservoirs, the flowing bottomhole pressure of the production well decreases. When the flowing bottomhole pressure decreases below the dewpoint, condensate accumulates near the wellbore region and forms a condensate bank. This results in a loss of productivity of both gas and condensate, which becomes more serious in intermediate- and low-permeability gas/condensate reservoirs, where the condensate bank reduces both the gas permeability and the well productivity. Several techniques have been used to mitigate this problem. These methods include: Use of solvents and wettability-alteration chemicals to reduce the impact of condensate blockage Gas cycling and injection of nitrogen and supercritical carbon dioxide as pressure-maintenance methods Drilling horizontal wells, hydraulic fracturing, and acidizing to improve the well productivity Gas cycling aims to keep the reservoir pressure greater than the dewpoint pressure to reduce the condensation phenomena. The limited volumes of gas that can be recycled in the reservoir can hinder the application of this method. For an ideal gas-cycling process, the volume of the gas injected into the reservoir will be larger than the total gas that can be produced from such a reservoir. Other approaches are the drilling of horizontal wells and hydraulic fracturing, during which the pressure drop around the wellbore region is lowered to allow for a longer production time, with only single-phase gas flow to the wellbore. These approaches are costly because they require drilling rigs. Another technique is the use of solvents, which shows good treatment outcomes, but the durability is a questionable issue in these treatments. Moreover, wettability alteration needs to be approached very carefully so as not to cause permanent damage to the reservoir. The use of fluorinated polymers and surfactants dissolved in alcohol-based solvents for wettability-alteration treatments was reported in many studies. Each method has its own advantages and disadvantages, and can be applied under certain conditions. This paper presents all of these methods, along with their advantages and disadvantages and description of some of their field applications and case studies.