Improving the Gas and Condensate Relative Permeability Using Chemical Treatments

Production from gas-condensate reservoirs having a bottom hole flowing pressure below the dewpoint pressure results in an accumulation of condensate near the wells causing a large decrease in both the gas and condensate relative permeability. Several methods such as hydraulic fracturing and solvents have been proposed to restore production rates but all of these methods have limitations or they are only effective for short periods of time. We have evaluated new surfactants using a methanol-water mixture as the solvent to treat cores under reservoir conditions. The surfactants have been tested under reservoir conditions using a variety of cores and found to be promising since they significantly increased the steady state relative permeability. Experiments were performed to evaluate the effectiveness of these surfactants at high temperature and high gas flow rates over a range of capillary numbers on the order of those near production wells. The productivity index for sandstone cores was improved by a factor of 2 to 3 for temperatures over the temperature range of 145 to 275 °F for the Novec FC 4430 polymeric surfactant in the methanol-water mixture. These treatments have the potential to greatly increase production at low cost since only the near well region of the reservoir blocked by the condensate needs to be treated.