Wettability alteration in gas-condensate carbonate reservoir using anionic fluorinated treatment

Abstract

During gas production from gas condensate reservoirs, as the bottom hole pressure drops below the dew point pressure, the liquids drop out and form condensate banking resulting in significant loss of gas and condensate productivity. A new method for stimulating gas-condensate wells, is changing the rock wettability in near well-bore regions by chemical treatments. In this study, a new chemical treatment was developed to alter the wettability of carbonate rocks from water-wet to intermediate gas-wet in order to enhance gas relative permeability. The treatment involves the use of an anionic fluoro-surfactant mixture with an optimized concentration and a solvent. Contact angle and spontaneous imbibition experiments were run to measure the wettability alterations. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX) and adsorption isotherms were also performed to monitor the amounts of surfactant solutions which were adsorbed on the rock surface. The increase in gas relative permeability was quantified by comparing the permeability before and after chemical treatments. The contact angles were increased and water and oil imbibitions were reduced significantly after the treatments. Finally, core flood tests revealed that the optimized treatment could enhance the gas relative permeability by a factor of 1.7 which demonstrated the ability in wettability alteration at reservoir conditions.