Single-well push–pull test for assessing potential impacts of CO2 leakage on groundwater quality in a shallow Gulf Coast aquifer in Cranfield, Mississippi

Developments since 2005 in understanding potential environmental impacts of CO2 leakage from geological storage

“…In terms of impact on drinking water quality, aside from a limited number of exceptions, trace element concentrations remained well below national and international drinking water limits in all field experiments in which they were measured Cahill et al, 2014;Kharaka et al, 2010;Mickler et al, 2013;Peter et al, 2012;Trautz et al, 2013;Yang et al, 2013a;Yang et al, 2014b). Exceptions included Al values over 10x the WHO guidelines (Cahill et al, 2014), two samples that exceeded Ni drinking water levels , and some pH, Fe, Mn and Zn values that exceeded secondary standard levels where effects are deemed to be cosmetic or aesthetic (Yang et al, 2014b).…”

“…In particular, numerous studies have found that reaction and element-release rates in laboratory batch experiments are 2 to 100 times higher than those observed in field experiments (Matter et al, 2007;Mickler et al, 2013;Yang et al, 2013a). These authors postulate that the unrealistically high water / rock ratios, reactive surface area (due to disaggregation), and mixing in batch experiments maintain mineral phases under saturated and thus mass transfer rates artificially high.…”

“…It is also being used to interpret observed groundwater changes at CO 2 injection field experiments Yang et al, 2013a;Yang et al, 2014b;Zheng et al, 2012). For these studies, the most commonly applied models are TOUGHREACT (Xu et al, 2004) and PHREEQC (Parkhurst and Appelo, 1999).…”

“…As the main pH control is provided by carbonates, several studies consider a simplified system using only calcite and aqueous carbonate species to predict impacts on pH and alkalinity in shallow groundwater (Carroll et al, 2014;Navarre-Sitchler et al, 2013;Yang et al, 2013a). In other cases, complex mineralogical characterization of geological formations has been obtained from core analyses (e.g.…”

“…In carbonate rich aquifers pH changes will be limited due to buffering but alkalinity and DIC will increase significantly with the dissolution of calcite or dolomite, whereas in carbonate poor aquifers pH will decrease sharply. Thus authors have suggested the use of DIC (Romanak et al, 2012b), DIC and pH (Trautz et al, 2013), or DIC, pH, and  13 C DIC (Yang et al, 2013a;Yang et al, 2013b), while Yang et al (2014b) used modelling results to suggest that pCO 2 and DIC may be the best compromise in all mineralogical settings. Some major ions, such as Ca, Mg, Fe, and Mn, have shown CO 2 induced changes in controlled injection experiments (Cahill et al, 2014;Kharaka et al, 2010;Trautz et al, 2013), however their reactivity means that data interpretation is problematic.…”