Fluoro-chemical foam injection for wettability alteration of sandstone and carbonate reservoirs rocks towards gas-wet state

Abstract

In gas condensate reservoirs, when fluid pressure decreases below its dew point pressure, it contributes to condensate build-up around the wellbore. Due to liquid condensation, gas and condensate relative permeability and mobility significantly drop and well productivity is considerably decreased. Several approaches have been recommended to mitigate condensate banking. Wettability alteration of the reservoir rock surface towards gas-wet is considered as one of the promising techniques for alleviating condensate banking. In this communication, a fluoro-chemical foam treatment technique is introduced to alleviate the condensate banking. To evaluate the effectiveness of the foam injection technique for the gas-wetting alteration of sandstone and carbonate cores, the contact angle measurement, liquid imbibition, and core displacement tests were conducted in the gas-liquid-core system. The adsorption of the fluoro-chemical solution on sandstone and carbonate samples was verified by surface analysis techniques including SEM, FTIR, and EDXS. The results show that the contact angles of brine and hexadecane droplets on the treated sandstone substrate increased from 0° and 0° to to135° and 103°, respectively. Moreover, treatment of carbonate substrate with fluoro-chemical solution resulted in an increase of 0° to 130° and 0° to 123° for brine and hexadecane contact angles, respectively. After treatment, the imbibition of brine and hexadecane liquids into the cores decreased significantly. Finally, the results of dynamic two-phase core flooding in sandstone and carbonate cores show that the chemical foam treatment can improve the end-point gas relative permeabilities by the factors of 1.704 and 1.69 for sandstone and carbonate cores, respectively.