A New Solution To Restore Productivity of Gas Wells With Condensate and Water Blocks

Abstract

Summary During production from gas-condensate reservoirs, significant productivity loss occurs after the pressure near the production wells drops below the dewpoint of the hydrocarbon fluid. Many of these gas reservoirs also have some water accumulation near the wells. This adds significantly to the total liquid blocking. Experiments were conducted using both outcrop sandstone and reservoir cores to measure the effect of liquid blocking on gas relative permeability. A chemical treatment was developed to reduce the damage caused by condensate and water blocking. The treatment is composed of a fluorinated material delivered in a unique and optimized glycol-alcohol solvent mixture. The chemical treatment alters the wettability of water-wet sandstone to neutral-wet and increases the gas relative permeability. The increase in gas relative permeability was quantified by comparing the gas relative permeabilities before and after treatment. Improvements in the gas relative permeability by a factor of approximately two were observed. The alteration of wettability after the chemical treatment was evaluated by measuring the USBM wettability index of treated reservoir cores. Measurements show that a significant amount of the surfactant is adsorbed on the rock surface, which is important for the durability of the treatment. Many attempts have been made to develop effective chemical treatments to mitigate the damage caused by condensate and/or water blocking with little success until now under realistic reservoir conditions. Using inexpensive, safe, and effective solvents was one of the keys to the success of our new approach. Other researchers have mostly tried reactive materials that are subject to complications in downhole applications. We use a nonreactive, nonionic polymeric surfactant that has none of these problems and is robust across a wide range of temperature, pressure, permeability, and brine salinity. We have developed a chemical treatment for liquid blocking that shows great potential to increase production from gas-condensate wells. Compositional simulations indicate that the economics of this treatment process is likely to be very favorable.