Abstract
Abstract During natural gas production from gas condensate reservoirs, due to drops in bottom hole pressure below the dew point, liquids drop out and form condensate blockage which results 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. The aim of this study was to employ two comparative methods of chemical treatments for altering the rock wettability from strong liquid-wetting to intermediate gas-wetting. First the surface of rocks was modified by using sol–gel process under acid- and/or base-catalyzed conditions. Then the effects of two different chemical treatments were examined by various experimental tests such as Fourier transform infrared (FTIR), thermogravimetric analyses (TGA), electron dispersive analysis of X-ray (EDX) and scanning electron microscopy (SEM) followed by static contact angle, coreflood test and porosity measurements. The results showed that, such methods could alter the wettability significantly. It was noticed that there were some differences in the experimental results related to sol–gel structure. Compared to a base-catalyzed process which showed higher contact angle value, an acid-catalyzed process tended to produce more linear branched-polymeric networks with fewer cross-linkages and could penetrate into the limestone core easier. The final evaluation of the coatings in terms of their effectiveness by coreflood test showed that the improvement factors were 0.78 and 0.56 for the acid- and base-catalyzed treatments, respectively.
Published Version
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