Southeastern Section - 64th Annual Meeting (19–20 March 2015)

Paper No. 5
Presentation Time: 8:00 AM-12:00 PM


EDENBORN, H.M., Geological & Environmental Systems Directorate, Research & Innovation Center, National Energy Technology Lab; U.S. Department of Energy, Pittsburgh, PA 15236 and VESPER, Dorothy J., Department of Geology and Geography, West Virginia University, 330 Brooks Hall, Morgantown, WV 26506,

Geological carbon capture and sequestration (CCS) has been proposed as a way to lessen global climate change due to fossil fuel combustion, but the potential migration of CO2 and mobilized pollutants to groundwater associated with these sites is a concern. The CarboQC carbonation meter is a method of CO2 analysis in water that is based on the ideal gas law by measuring equilibrium temperature and pressure resulting from the multiple expansion of a sealed sample volume. This method is effective using carbonated beverages and most natural waters because the solubility of potentially interfering O2 and N2 gases is over 50 times lower in water than it is for CO2. However, hydrogen sulfide (H2S), which is even more soluble than CO2 in water, is occasionally encountered in very high concentrations in groundwater samples, especially those associated with high-S petroleum deposits or natural gas production. In this study, we examined the effects of H2S associated with water samples from a natural spring in Virginia and saline produced waters from enhanced oil recovery (EOR) wells in Texas on the measurement of CO2 using the CarboQC meter. Both copper sulfate and zinc acetate were tested as ways of eliminating the H2S fraction via precipitation of metal sulfides and determining the CO2 concentration by difference. Copper sulfide was rapidly precipitated in EOR well samples containing 500-800 mg/L H2S, but the reaction simultaneously lowered the pH to ca. 1.5. As a result, detectable CO2 levels were actually increased due to the net acidification of the sample. The potential for this analytical approach to be effective in such waters is considered and discussed relative to recently observed effects on the mutual interaction between the two gases and their respective solubilities in water.