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REACTIVE TRANSPORT MODELLING OF DISSOLVED CO2 IN POROUS MEDIA: Injection into and leakage from geological reservoirs
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering. KTH Royal Institute of Technology. (Doctoral Program in Land and Water Resources Engineering)ORCID iD: 0000-0002-6871-8540
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The geological sequestration of carbon dioxide (CO2) is one of the options of controlling the greenhouse gas emissions. However, leakage of CO2 from the storage reservoir is a risk associated with geological sequestration. Over longer times, large-scale groundwater motion may cause leakage of dissolved CO2 (CO2aq).

The objectives of this thesis are twofold. First, the modelling study analyzes the leakage of CO2aq along the conducting pathways. Second, a relatively safer mode of geological storage is investigated wherein CO2aq is injected in a carbonate reservoir. A reactive transport model is developed that accounts for the coupled hydrological transport and the geochemical reactions of CO2aq in the porous media. The study provides a quantitative assessment of the impact of advection, dispersion, diffusion, sorption, geochemical reactions, temperature, and heat transport on the fate of leaking CO2aq.

The mass exchange between the conducting pathway and the rock matrix plays an important role in retention and reactions of leaking CO2aq. A significant retention of leaking CO2aq is caused by its mass stored in aqueous and adsorbed states and its consumption in reactions in the rock matrix along the leakage pathway. Advection causes a significant leakage of CO2aq directly from the reservoir through the matrix in comparison to the diffusion alone in the rock matrix and advection in a highly conducting, but thin fracture. Heat transport by leaking brine also plays an important role in geochemical interactions of leaking CO2aq

Injection of CO2aq is simulated for a carbonate reservoir. Injected CO2-saturated brine being reactive causes fast dissolution of carbonate minerals in the reservoir and fast conversion of CO2aq through considered geochemical reactions. Various parameters like dispersion, sorption, temperature, and minerals reaction kinetics are found to play important role in the consumption of CO2aq in reactions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , xii, 59 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; 2016-04
Keyword [en]
CO2 geological storage and safety, leakage of brine saturated with dissolved CO2, reactive transport, fracture, advection, dispersion and diffusion, sorption, carbonate minerals kinetic reactions, calcite, dolomite, siderite, porosity, permeability, heat transport
National Category
Mineral and Mine Engineering
Research subject
Land and Water Resources Engineering
Identifiers
URN: urn:nbn:se:kth:diva-184204ISBN: 978-91-7595-911-5OAI: oai:DiVA.org:kth-184204DiVA: diva2:915621
Public defence
2016-04-20, F3, Lindstedstsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
StandUpSwedish Research Council, VR621-2007-4440
Note

Research Funders:

(i) Higher Education Commission (HEC) of Pakistan

(ii) Lars Erik Lundberg Scholarship Foundation, Sweden

Available from: 2016-04-04 Created: 2016-03-30 Last updated: 2016-05-02Bibliographically approved
List of papers
1. Reactive transport modeling of leaking CO2-saturated brine along a fractured pathway
Open this publication in new window or tab >>Reactive transport modeling of leaking CO2-saturated brine along a fractured pathway
2015 (English)In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 42, 672-689 p.Article in journal (Refereed) Published
Abstract [en]

One concern regarding the underground storage of carbon dioxide (CO2) is its potential leakage from reservoirs. Over short period of time, the leakage risk is related mainly to CO2 as a separate supercritical fluid phase. However, over longer periods upon complete dissolution of injected CO2 in the fluid, the leakage risk is associated with dissolved phase CO2. Over the geological time scales, large-scale groundwater motion may cause displacement of brine containing dissolved CO2 along the conducting pathways. In this paper, we present a comprehensive modeling framework that describes the reactive transport of CO2-saturated brine along a fracture in the clay caprock based on the future, hypothetical leakage of the dissolved phase CO2. This study shows that the transport of leaked dissolved CO2 is significantly retarded by a combination of various physical and geochemical processes, such as mass exchange between conducting fracture and the neighboring rock matrix through molecular diffusion, sorption and calcite dissolution in the rock matrix. Mass stored in aqueous and adsorbed states in the rock matrix caused retention of dissolved CO2 along the leakage pathway. Calcite dissolution reaction in the rock matrix resulted in consumption of leaking dissolved CO2 and reduced its mass along the leakage pathway. Consumption and retention of dissolved CO2 along the leakage pathway have important implications for analyzing the potential reduction of CO2 fluxes from storage reservoirs over large periods and long travel pathways.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
CO2-saturated brine leakage, Reactive transport, Fracture, Matrix diffusion, Sorption, Calcite kinetic reaction
National Category
Geochemistry
Identifiers
urn:nbn:se:kth:diva-180631 (URN)10.1016/j.ijggc.2015.09.001 (DOI)000366947400061 ()2-s2.0-84945326226 (ScopusID)
Funder
StandUp
Note

QC 20160121

Available from: 2016-01-21 Created: 2016-01-19 Last updated: 2016-04-04Bibliographically approved
2. Non-isothermal reactive transport modelling of dissolved CO2 leaking through a fractured caprock
Open this publication in new window or tab >>Non-isothermal reactive transport modelling of dissolved CO2 leaking through a fractured caprock
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Geological storage of CO2 is considered as one of the mitigation actions for climate change adverse effects. However, some fraction of CO2 dissolved in the brine following injection, may leak from the reservoir through permeable zones such as conducting fractures. In this study we perform the reactive transport modelling of single-phase brine saturated with dissolved CO2 (CO2aq) along a conducting fracture in a clay-rich caprock. This study investigates the role of temperature and various reaction systems on the fate of migrating CO2aq, its geochemical interactions with the carbonate minerals, its conversion in geochemical reactions and associated medium porosity and permeability evolutions along the transport pathway.About 0.64% of leaking CO2aq is found converted into other ions in its geochemical interactions with calcite (simplified geochemical system). Addition of mineral dolomite in the geochemical system (extended geochemical system) results in up to 11% higher mass conversion of CO2 in reactions as compared to the simplified geochemical system. Considering extended geochemical system and heat transport by moving brine resulted in about 27.34% higher mass conversion of CO2 in reactions as compared to the simplified geochemical system. A combination of extended geochemical system, heat transport and sorption resulted in about 82.59% higher mass conversion of CO2 compared to the simplified geochemical system. Leaking CO2aq travelled less than 250 m along the fractured pathway, for a velocity of nearly 19 m/year in the fracture, due to retardation caused by mass stored in aqueous and adsorbed states.

Keyword
Reactive transport, Brine carrying dissolved CO2, Conducting fracture, Kinetics of calcite and dolomite, Heat transport, Sorption
National Category
Mineral and Mine Engineering
Research subject
Applied and Computational Mathematics; Chemical Engineering; Civil and Architectural Engineering; Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-184623 (URN)
Funder
StandUp
Note

This manuscript was submitted to the journal of Water Resources Research. The main funder for this study has been “Higher Education Commission (HEC) of Pakistan”. The study was also partly supported by Lars Erik Lundberg Scholarship Foundation, Sweden.

Available from: 2016-04-01 Created: 2016-04-01 Last updated: 2016-04-04Bibliographically approved
3. The role of advection and dispersion in the rock matrix on the transport of leaking CO2-saturated brine along a fractured zone
Open this publication in new window or tab >>The role of advection and dispersion in the rock matrix on the transport of leaking CO2-saturated brine along a fractured zone
(English)Manuscript (preprint) (Other academic)
Abstract [en]

CO2 that is injected into a storage reservoir can leak in dissolved form because of brine displacement from the reservoir, which is caused by large-scale groundwater motion. Simulations of the reactive transport of leaking CO2aq along a conducting fracture in a clay-rich caprock are conducted to analyze the effect of various physical and geochemical processes. Whilst several modelling transport studies along rock fractures have considered diffusion as the only transport process in the surrounding rock matrix (diffusive transport), this study analyzes the combined role of advection and dispersion in the rock matrix in addition to diffusion (advection-dominated transport) on the migration of CO2aq along a leakage pathway and its conversion in geochemical reactions. A sensitivity analysis is performed to quantify the effect of fluid velocity and dispersivity. Variations in the porosity and permeability of the medium are observed in response to calcite dissolution and precipitation along the leakage pathway. We observe that advection and dispersion in the rock matrix play a significant role in the overall transport process. For the parameters that were used in this study, advection-dominated transport increased the leakage of CO2aq from the reservoir by nearly 305%, caused faster transport and increased the mass conversion of CO2aq in geochemical reactions along the transport pathway by approximately 12.20% compared to diffusive transport. 

Keyword
Reactive transport, Advection dominated transport, Diffusive transport, CO2-saturated brine leakage, Transport in fractures, Rock matrix, Calcite kinetic reaction
National Category
Mineral and Mine Engineering
Research subject
Civil and Architectural Engineering; Chemical Engineering; Applied and Computational Mathematics; Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-184616 (URN)
Funder
StandUp
Note

This manuscript is under review in the journal of Advances in Water Resources. The main funder for this study has been “Higher Education Commission (HEC) of Pakistan”. The study was also partly supported by Lars Erik Lundberg Scholarship Foundation, Sweden.

Available from: 2016-04-01 Created: 2016-04-01 Last updated: 2016-04-04Bibliographically approved
4. Injection of CO2-saturated brine in geological reservoir: A way to enhanced storage safety
Open this publication in new window or tab >>Injection of CO2-saturated brine in geological reservoir: A way to enhanced storage safety
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Injection of free phase supercritical CO2 into deep geological reservoirs is associated with risk of considerable return flows towards the land surface due to the buoyancy of CO2, which is lighter than the resident brine in the reservoir. Such upward movements can be avoided if CO2 is injected in the dissolved phase (CO2aq). In this work, injection of CO2-saturated brine in a subsurface carbonate reservoir is modelled. Physical and geochemical interactions of injected low-pH CO2-saturated brine with the carbonate minerals (calcite, dolomite and siderite) are investigated in the reactive transport modelling. CO2-saturated brine, being low in pH, shows high reactivity with the reservoir minerals, resulting in a significant mineral dissolution and CO2 conversion in reactions. Over the injection period of 10 years, up to 16% of the injected CO2 is found consumed in geochemical reactions. Sorption included in the transport analysis resulted in additional quantities of CO2 mass stored. However, for the considered carbonate minerals, the consumption of injected CO2aq is found mainly in the form of ionic trapping.

Keyword
Injection of CO2-saturated brine, geological storage, carbonate reservoir, carbonate mineral reactions, ionic trapping, enhanced storage safety
National Category
Mineral and Mine Engineering
Research subject
Applied and Computational Mathematics; Chemical Engineering; Chemistry; Civil and Architectural Engineering; Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-184624 (URN)
Funder
StandUp
Note

This manuscript was submitted to the journal of International Journal of Greenhouse gas Control. The main funder for this study has been “Higher Education Commission (HEC) of Pakistan”. The study was also partly supported by Lars Erik Lundberg Scholarship Foundation, Sweden.

Available from: 2016-04-01 Created: 2016-04-01 Last updated: 2016-04-04Bibliographically approved

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