Uncertainties of geochemical modeling during CO2 sequestration applying batch equilibrium calculations

Abstract

One of the uncertainties in the field of carbon dioxide capture and storage (CCS) is caused by the parameterization of geochemical models. The application of geochemical models contributes significantly to calculate the fate of the CO 2 after its injection. The choice of the thermodynamic database used, the selection of the secondary mineral assemblage as well as the option to calculate pressure dependent equilibrium constants influence the CO 2 trapping potential and trapping mechanism. Scenario analyses were conducted applying a geochemical batch equilibrium model for a virtual CO 2 injection into a saline Keuper aquifer. The amount of CO 2 which could be trapped in the formation water and in the form of carbonates was calculated using the model code PHREEQC. Thereby, four thermodynamic datasets were used to calculate the thermodynamic equilibria. Furthermore, the equilibrium constants were re-calculated with the code SUPCRT92, which also applied a pressure correction to the equilibrium constants. Varying the thermodynamic database caused a range of 61% in the amount of trapped CO 2 calculated. Simultaneously, the assemblage of secondary minerals was varied, and the potential secondary minerals dawsonite and K-mica were included in several scenarios. The selection of the secondary mineral assemblage caused a range of 74% in the calculated amount of trapped CO 2 . Correcting the equilibrium constants with respect to a pressure of 125 bars had an influence of 11% on the amount of trapped CO 2 . This illustrates the need for incorporating sensitivity analyses into reaction pathway modeling.

Investigation of caprock integrity for CO2 sequestration in an oil reservoir using a numerical method

“…Over the last few years, the issues involved in underground CO 2 sequestration have been included in the scientific literature mainly from a fluid property, fluid-dynamical, and geochemical viewpoint (e.g., Dethlefsen et al, 2012;Gysi and Stefansson, 2012;Balashov et al, 2013;Hosein and Alshakh, 2013;Poordad and Forutan, 2013)), but relatively fewer works have focused on the related geomechanical processes especially caprock integrity during CO 2 injection (e.g., Shukla et al, 2011;Dempsey et al, 2014;Vilarrasa, 2014)). …”

A model comparison initiative for a CO2 injection field test: an introduction to Sim-SEQ

“…In practice, however, GCS is unlikely to be perfectly effective or completely risk-free (Oldenburg et al, 2009;Birkholzer et al, 2011). This is because there are still considerable uncertainties regarding storage capacity, injectivity, caprock integrity, leakage pathways, impact on reservoir rock and formation fluids, and effectiveness of post-injection monitoring of the injected CO 2 plume (Wilson et al, 2007;Stauffer et al, 2009;Li et al, 2011;Seto et al, 2011;Dethlefsen et al, 2012). Convincing scientific research targeted at resolving and quantifying these uncertainties is needed to assure policy makers (and the public in general) that GCS is a viable technology and that it can be deployed with adequate safeguards (Kang et al, 2010).…”

Suitability of Existing Numerical Model Codes and Thermodynamic Databases for the Prognosis of Calcite Dissolution Processes in Near-Surface Sediments Due to a CO2 Leakage Investigated by Column Experiments

“…In this study, the pressure effect on the equilibrium constants (log_k) of calcite, CO 2 and the aquatic species was not considered, because Fahrner et al (2012) and Dethlefsen et al (2012) determined the influence of the pressure on the equilibrium constants as a minor factor.…”