Research Project on CO2 Geological Storage and Groundwater Resources: Water Quality Effects Caused by CO2 Intrusion into Shallow Groundwater

Modeling Studies on the Transport of Benzene and H2S in CO2-Water Systems

“…Measured (Xia et al, 2000) and calculated H 2 S solubilities in 6M NaCl solution at 80 o C (right) and 120 o C (left). 116 In the first part of an EPA-funded project on potential effects of carbon capture and geologic storage (CCS) on groundwater resources (Birkholzer et al, 2008), we evaluated the potential for mobilization of trace elements in response to CO 2 intrusion via systematic reactive-transport simulations involving hypothetical release scenarios Apps et al, 2010). Other researchers have investigated this issue by laboratory experiments (e.g., Carroll, 2009;McGrath et al, 2007;Smyth et al, 2009) as well as modeling work integrated with controlled field experiments of CO 2 release in freshwater aquifers (e.g., Kharaka et al, 2010;Ambats et al, 2009).…”

“…A third model was used to evaluate the potential consequences of CO 2 plus H 2 S leaking into a hypothetical shallow groundwater aquifer (Section 5.3). The setup of this third model, including hydrogeologic properties, initial chemical composition of groundwater, and chemical reaction network, is described in Section 5.3.1 and is similar to that adopted in the first part of this project (Birkholzer et al, 2008;Zheng et al, 2009). The differences from the previous model setup are: (1) a mixture of 95% CO 2 and 5% H 2 S instead of pure CO 2 is considered; and (2) arsenic sulfides (orpiment, As 2 S 3 , and realgar, As 4 S 4 ) are added to the list of potentially forming secondary phases.…”

“…In the present case, sediments of the shallow aquifer are assumed to contain about 28 ppm of arsenic and 12 ppm of lead (Table 5.7). Average crustal abundance of arsenic and lead is about 2 and 14 ppm, respectively, as summarized in Birkholzer et al (2008) based on an extensive literature review. Typical concentrations in rock from various areas of the United States were reviewed by Connor and Shacklette (1975), who list 1.1-4.3 ppm As and 5-17 ppm Pb in sandstones, and 6.4-9.0 ppm As and 11-24 ppm Pb in shales.…”

Reactive transport modeling for CO2 geological sequestration

“…This includes the mineralogical composition of aquifer, the aqueous composition of the groundwater and the distribution of the trace elements between different phases. Three types of aquifer have been considered in Birkholzer et al, (2008) and here we will focus on the one type, or the St Peter Sandstone in Illinoise Basin (Pitman et al, 1997). The mineralogical composition is listed in Table 1.…”

“…(Birkholzer et al, 2008), it is understood that even the most comprehensive sensitivity study can neither encompass all possible conditions and scenarios, nor can it account for all relevant uncertainties. As stated in Apps et al (2010), it was recommend that "the generic study should be followed up with site-specific model predictions, and that laboratory or field experiments should be performed to test uncertain model assumptions and parameters.…”