Water injection at The Geysers, California, has acted to sustain reservoir pressures and production rates, as well as to improve steam composition by reducing the content of non-condensible gases (NCGs). Improved steam composition is thought to result from producing steam formed from boiling the relatively clean injection water, and from increased pressurization that decreases the production of deeper native steam having large NCG concentrations. A possible additional effect that could lower NCG concentrations in produced steam is dissolution in a condensed aqueous phase that would form due to reservoir repressurization from injection-derived steam (IDS).

We are performing laboratory experiments to evaluate the dissolution of hydrogen chloride (HCl) gas in the injection-derived condensation. In the experiments, we form a condensed water phase by water vapor sorption and capillary condensation in a porous medium, and then introduce hydrogen chloride gas. The pressure decline caused by dissolution of the HCl into the condensed water phase, and possible interaction with solid surfaces are used to provide kinetic information on the sorption process, and endpoint HCl vapor concentrations are verified analytically. Preliminary results show strong HCl sorption to silica surfaces, rock wettability changes due to HCl interaction at very low water contents, and HCl scrubbing from the vapor phase. Our experiments suggest an additional effect that promotes vapor condensation and HCl scrubbing, namely, vapor pressure lowering due to HCl dissolution, and subsequent increase in ionic strength of the condensed phase.

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