The problem of condensate blocking in low permeability gas-condensate reservoirs is greatly affected by the rock-fluid interactions and capillary trapping. Many publications suggest wettability alteration to gas-wetting as a permanent solution to the problem. In this work, we present a simulation study on the optimum wettability conditions for maximum gas-condensate well productivity enhancement. Most of the work in this area focuses on reversal of wetting conditions from liquid-wetting (contact angle of 0 degree) to gas-wetting (with contact angle around 150 degrees). On the experimental side, chemicals are tested in its ability to change wettability. On the simulation side, research shows that changing the wettability to gas-wetting in the near wellbore region results in better productivity than the original liquid-wetting state. Our work investigates various states of wettability ranging from liquid-wetting to gas-wetting and its effect on gas-condensate well productivity. We also study the effect of reservoir permeability, reservoir pressure and treatment radius on the well productivity enhancement by wettability alteration.

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In gas condensate reservoirs, deliverability starts to decrease when retrograde condensation occurs. As the bottom-hole pressure drops below the dew-point, gas condensate and water build-up impede flow of gas to the wellbore. In order to stop the reduction in productivity, many publications suggest wettability alteration to gas-wetting as a permanent solution to the problem. Previous simulation work suggests an "optimum wetting state" to exist where maximum gas condensate well productivity is reached. This work has direct application in gas-condensate reservoirs, especially in identifying the most effective stimulation treatment which can be designed to provide the optimum wetting conditions in the near-wellbore region.In this work, we aim to show the existence of such an optimum state of wettability that result in maximum gas mobility and in an increase of the relative permeability curves. We present an experimental study on Berea sandstone rocks treated with a fluorinated polymer and investigate the optimum fluorinated polymer concentration that would alter the wettability to intermediate gas-wet. Different experimental techniquesincluding flow tests and spontaneous imbibition are conducted to examine the effect of treatments on wettability. Interaction between rocks and the fluids is studied using a MicroCT scanner.The studies in this area are important to improve the productivity of gas condensate reservoirs where liquid accumulates, decreasing production of the well. Efficiency in the extraction of natural gas is important for the economic and environmental considerations of the oil and gas industry. Wettability alteration is one of the newest stimulation methods proposed by researchers, and shows great potential for future field applications and further research studies.

Trapping of spent acid after acidizing job is a major problem in carbonate rocks. Spent acid needs to be fully mobilized and recovered in order to enhance gas production. Wettability of the rocks and capillary forces are the main reason behind fluid trapping in carbonate formations. These forces can be weakened by decreasing surface tension and increasing contact angle. Additives that are injected along with the acid can have an impact on changing the surface tension, contact angle and possibly the wettability of the rocks. Previously, separate studies were conducted on the effect of acid additives on contact angle and surface tension. However, there is still a need to investigate the overall impact of acid additives on these two parameters and wettability on the trapping of spent acid in the carbonate rocks. In this paper, the full impact of two additives, formic acid and methanol, on trapping and wettability is investigated. Irreducible fluid saturation is compared before and after the exposure of rocks to spent acid. Formic acid decreased irreducible fluid saturation whereas methanol increased irreducible fluid saturation. Spontaneous water imbibition was conducted in each case to ensure that there is no permanent effect on rock wettability as a result of using these additives. It is very important to understand that the effect of various additives on wettability must be studied before any acid job, as their impact on wettability can consequently affect well productivity.