The Effect of Hydrogen Sulfide Concentration on Gel as Water Shutoff Agent

For drilling and water shutoff of oil and gas reservoirs containing hydrogen sulfide (H2S), the effects of H2S on widely used gel as water shutoff agents are studied. The gels include Na2Cr2O7/Na2SO3/HPAM gel, Na2Cr2O7/(NH2)(2)CS/HPAM gel, Cr(III)-acetate & Cr(III)-lactate/HPAM gel and phenol formaldehyde resin/HPAM gel. The results show that: - for Na2Cr2O7/Na2SO3/HPAM gel and Na2Cr2O7/(NH2)(2)CS/HPAM gel, the H2S as reducing agent (the reducibility is more efficient than that of Na2SO3 and (NH2)(2)CS) can reduce Cr(VI) into Cr(III) and accelerate crosslinking reaction with HPAM in low concentration of H2S, while it can react with Cr(III) generating Cr2S3 precipitation in high concentration of H2S, for which the bulk gel can not form without Cr(III); - for Cr(III) -acetate & Cr(III)-lactate/HPAM gel, H2S can prolong the gelation time and reduce the gel strength by decreasing pH value; - for phenol formaldehyde resin/HPAM gel, H2S can slightly prolong the gelation time and slightly reduce the gel strength by decreasing pH value. Therefore, according to the comprehensive investigations of the effects of H2S on gel as water shutoff agents, the phenol formaldehyde resin/HPAM gel is recommended as the water shutoff agents suitable for oil and gas reservoir containing H2S.Energy & FuelsEngineering, ChemicalEngineering, PetroleumSCI(E)EI1ARTICLE2355-3616