Development of a Hybrid Process and System Model for the Assessment of Wellbore Leakage at a Geologic CO<sub>2</sub> Sequestration Site

Viswanathan, Hari; Pawar, Rajesh J.; Stauffer, Philip H.; Kaszuba, John P.; Carey, J. William; Olsen, S. C.; Keating, Gordon N.; Kavetski, Dmitri; Guthrie, George D.

doi:10.1021/es800417x

Cited by 144 publications

(102 citation statements)

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“…The transport of trace metals to the shallow aquifer is critical for assessing shallow subsurface impacts due to brine or CO 2 intrusion. The effective retardation of trace metals is an important parameter to evaluate in performance assessment studies (Viswanathan et al, 2008) and is dependent on multiple coupled reactions.…”

Section: Reactive Transport Modelmentioning

confidence: 99%

Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO2 sequestration natural analog site in Chimayo, New Mexico

Viswanathan

Dai

Lopano

et al. 2012

International Journal of Greenhouse Gas Control

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a b s t r a c tMigration of carbon dioxide (CO 2 ) from deep storage formations into shallow drinking water aquifers is a possible system failure related to geologic CO 2 sequestration. A CO 2 leak may cause mineral precipitation/dissolution reactions, changes in aqueous speciation, and alteration of pH and redox conditions leading to potential increases of trace metal concentrations above EPA National Primary Drinking Water Standards. In this study, the Chimayo site (NM) was examined for site-specific impacts of shallow groundwater interacting with CO 2 from deep storage formations. Major ion and trace element chemistry for the site have been previously studied. This work focuses on arsenic (As), which is regulated by the EPA under the Safe Drinking Water Act and for which some wells in the Chimayo area have concentrations higher than the maximum contaminant level (MCL). Statistical analysis of the existing Chimayo groundwater data indicates that As is strongly correlated with trace metals U and Pb indicating that their source may be from the same deep subsurface water. Batch experiments and materials characterization, such as: X-ray diffraction (XRD), scanning electron microscopy (SEM), and synchrotron micro X-ray fluorescence (-XRF), were used to identify As association with Fe-rich phases, such as clays or oxides, in the Chimayo sediments as the major factor controlling As fate in the subsurface. Batch laboratory experiments with Chimayo sediments and groundwater show that pH decreases as CO 2 is introduced into the system and buffered by calcite. The introduction of CO 2 causes an immediate increase in As solution concentration, which then decreases over time. A geochemical model was developed to simulate these batch experiments and successfully predicted the pH drop once CO 2 was introduced into the experiment. In the model, sorption of As to illite, kaolinite and smectite through surface complexation proved to be the key reactions in simulating the drop in As concentration as a function of time in the batch experiments. Based on modeling, kaolinite precipitation is anticipated to occur during the experiment, which allows for additional sorption sites to form with time resulting in the slow decrease in As concentration. This mechanism can be viewed as trace metal "scavenging" due to sorption caused secondary mineral precipitation. Since deep geologic transport of these trace metals to the shallow subsurface by brine or CO 2 intrusion is critical to assessing environmental impacts, the effective retardation of trace metal transport is an important parameter to estimate and it is dependent on multiple coupled reactions. At the field scale, As mobility is retarded due to the influence of sorption reactions, which can affect environmental performance assessment studies of a sequestration site.

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Section: Reactive Transport Modelmentioning

confidence: 99%

Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO2 sequestration natural analog site in Chimayo, New Mexico

Viswanathan

Dai

Lopano

et al. 2012

International Journal of Greenhouse Gas Control

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“…Any CO2 that escapes the reservoir is then available for transport toward either (1) the atmosphere (as in the case of risk due to exposure to high levels of CO2), (2) (15).…”

Section: Model Descriptionmentioning

confidence: 99%

A System Model for Geologic Sequestration of Carbon Dioxide

Stauffer

Viswanathan

Pawar

et al. 2008

Environ. Sci. Technol.

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In this paper we describe CO 2 -PENS, a comprehensive systemlevel computational model for performance assessment of geologic sequestration of CO 2 . CO 2 -PENS is designed to perform probabilistic simulations of CO 2 capture, transport, and injection in different geologic reservoirs. Additionally, the longterm fate of CO 2 injected in geologic formations, including possible migration out of the target reservoir, is simulated. The simulations sample from probability distributions for each uncertain parameter, leading to estimates of global uncertainty that accumulate through coupling of processes as the simulation time advances. Each underlying process in the systemlevel model is built as a module that can be modified as the simulation tool evolves toward more complex problems. This approach is essential in coupling processes that are governed by different sets of equations operating at different timescales. We first explain the basic formulation of the system level model, briefly discuss the suite of process-level modules that are linked to the system level, and finally give an indepth example that describes the system level coupling between an injection module and an economic module. The example shows how physics-based calculations of the number of wells required to inject a given amount of CO 2 and estimates of plume size can impact long-term sequestration costs.

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“…The existence of potential CO 2 leakage pathways and estimates of CO 2 leakage have been discussed extensively in the literature (Lewicki et al, 2007;Celia and Nordbotten, 2009;Shukla et al, 2010). However, current leakage risk assessment models (e.g., LeNeveu, 2008;Viswanathan et al, 2008) do not account for geochemical alterations of potential leakage pathways in caprock formations, and thus, may estimate inaccurate CO 2 or brine leakage rates along a reactive pathway, such as that of a fractured carbonate caprock (Ellis et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Dissolution-Driven Permeability Reduction of a Fractured Carbonate Caprock

Ellis

Fitts

Bromhal

et al. 2013

Environmental Engineering Science

128

117

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Geochemical reactions may alter the permeability of leakage pathways in caprocks, which serve a critical role in confining CO 2 in geologic carbon sequestration. A caprock specimen from a carbonate formation in the Michigan sedimentary Basin was fractured and studied in a high-pressure core flow experiment. Inflowing brine was saturated with CO 2 at 40°C and 10 MPa, resulting in an initial pH of 4.6, and had a calcite saturation index of -0.8. Fracture permeability decreased during the experiment, but subsequent analyses did not reveal calcite precipitation. Instead, experimental observations indicate that calcite dissolution along the fracture pathway led to mobilization of less soluble mineral particles that clogged the flow path. Analyses of core sections via electron microscopy, synchrotron-based X-ray diffraction imaging, and the first application of microbeam Ca K-edge X-ray absorption near edge structure, provided evidence that these occlusions were fragments from the host rock rather than secondary precipitates. X-ray computed tomography showed a significant loss of rock mass within preferential flow paths, suggesting that dissolution also removed critical asperities and caused mechanical closure of the fracture. The decrease in fracture permeability despite a net removal of material along the fracture pathway demonstrates a nonintuitive, inverse relationship between dissolution and permeability evolution in a fractured carbonate caprock.

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Development of a Hybrid Process and System Model for the Assessment of Wellbore Leakage at a Geologic CO₂ Sequestration Site

Cited by 144 publications

References 12 publications

Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO2 sequestration natural analog site in Chimayo, New Mexico

Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO2 sequestration natural analog site in Chimayo, New Mexico

A System Model for Geologic Sequestration of Carbon Dioxide

Dissolution-Driven Permeability Reduction of a Fractured Carbonate Caprock

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Development of a Hybrid Process and System Model for the Assessment of Wellbore Leakage at a Geologic CO2 Sequestration Site

Cited by 144 publications

References 12 publications

Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO2 sequestration natural analog site in Chimayo, New Mexico

Developing a robust geochemical and reactive transport model to evaluate possible sources of arsenic at the CO2 sequestration natural analog site in Chimayo, New Mexico

A System Model for Geologic Sequestration of Carbon Dioxide

Dissolution-Driven Permeability Reduction of a Fractured Carbonate Caprock

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Development of a Hybrid Process and System Model for the Assessment of Wellbore Leakage at a Geologic CO₂ Sequestration Site