Water-blocked low permeability gas formations with drawdown pressures comparable to capillary entry pressures can take a very long time to clean up. The clean up of water blocks in gas wells occurs in two regimes: displacement of the fluids from the formation followed by vaporization by the flowing gas, which becomes under-saturated as the pressure decreases.

This work aims to study the effect of rock permeability, wettability, temperature, drawdown and surfactants on the clean up of cores containing brine. The effectiveness of using solvents for cleanup under different conditions has been evaluated by comparing gas relative permeabilities with and without methanol.

Gas displacement experiments were conducted on cores fully saturated with brine. The gas relative permeability increases with pore volumes of gas injected for long periods of time (up to 100,000 PV) at ambient temperature. The addition of methanol, increasing temperature and increasing core permeability resulted in faster cleanup after about 50 to 100 PV of gas flow. The change of wettability of the rock from water-wet to oil-wet also resulted in faster recoveries in gas relative permeability.

Our observations show that the clean up of water-blocks can be improved by: 1. Influencing the displacement of brine, i.e. by changing the wettability and, 2. By increasing the rate of vaporization by introducing volatile solvents such as methanol. It is found that changing wettability also has an impact on the rate of vaporization of the brine and methanol.

The study quantifies the effects of factors such as rock permeability, wettability, surface tension, and temperature on gas relative permeability. The results of this study will help in selecting strategies for clean-up of water blocks created due to various operations such as drilling and fracturing, and making recommendations for the use of surfactants or solvents for well treatments for removing water blocks.