A Physicochemical Prediction of Prolonged Natural CO2 Leakage in the Little Grand Wash Fault Zone, Green River, Utah

Abstract

Physicochemical investigation on a natural CO2 system and the accommodated fault-controlled fluids using a geochemical modeling method provides important information regarding the security assessment for geological carbon sequestration (GCS), which is the most promising method for enhancing our knowledge of the side effects of GCS. By employing an utilized series of regional fluid chemistry and hydrogeologic parameters, this study investigated the consequences caused by migration of CO2 in a naturally leaking CO2 system that developed in normal faults in the southwestern U.S. 1-D and 2-D models were conducted using the multi-phase, multi-component reactive transport simulator, TOUGHREACT, to establish sets of descriptive and interpretive data elaborating the heterogeneous water-rock-CO2 interactions such as diagenetic quartz and phyllosilicate, and reduction of iron oxide observed on fault traces in the region. Converging evidences from silicate mineral alterations and subsurface carbonate deposits examined in the study suggest that the fault conduit has a potential to be clogged as a consequence of CO2-bearing fluid migration. Results showed that continuous CO2 leakage in the same location is unlikely to happen because of: (i) a precipitation process involving diagenetic quartz and clay growths that are stable in the given condition of water chemistry and (ii) subsurface carbonate deposition that enhances the sealing capability of a fault zone. Additionally, the bleaching phenomena observed in this study showed that CO2 is the main cause of Fe mobilization in the region, without influence of methane and hydrocarbon.