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Weber UW, Rinaldi AP, Roques C, Wenning QC, Bernasconi SM, Brennwald MS, Jaggi M, Nussbaum C, Schefer S, Mazzotti M, Wiemer S, Giardini D, Zappone A, Kipfer R. In-situ experiment reveals CO 2 enriched fluid migration in faulted caprock. Sci Rep 2023; 13:17006. [PMID: 37813929 PMCID: PMC10562487 DOI: 10.1038/s41598-023-43231-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 09/21/2023] [Indexed: 10/11/2023] Open
Abstract
The sealing characteristics of the geological formation located above a CO2 storage reservoir, the so-called caprock, are essential to ensure efficient geological carbon storage. If CO2 were to leak through the caprock, temporal changes in fluid geochemistry can reveal fundamental information on migration mechanisms and induced fluid-rock interactions. Here, we present the results from a unique in-situ injection experiment, where CO2-enriched fluid was continuously injected in a faulted caprock analogue. Our results show that the CO2 migration follows complex pathways within the fault structure. The joint analysis of noble gases, ion concentrations and carbon isotopes allow us to quantify mixing between injected CO2-enriched fluid and resident formation water and to describe the temporal evolution of water-rock interaction processes. The results presented here are a crucial complement to the geophysical monitoring at the fracture scale highlighting a unique migration of CO2 in fault zones.
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Affiliation(s)
| | | | - Clément Roques
- Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
- Centre for Hydrogeology and Geothermics, University of Neuchâtel, Neuchâtel, Switzerland
| | - Quinn C Wenning
- Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
| | | | - Matthias S Brennwald
- Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
| | - Madalina Jaggi
- Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
| | | | | | - Marco Mazzotti
- Institute of Energy and Process Engineering, ETH Zürich, Zürich, Switzerland
| | - Stefan Wiemer
- Swiss Seismological Service, ETH Zürich, Zürich, Switzerland
| | | | - Alba Zappone
- Swiss Seismological Service, ETH Zürich, Zürich, Switzerland.
- Institute of Energy and Process Engineering, ETH Zürich, Zürich, Switzerland.
| | - Rolf Kipfer
- Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
- Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
- Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland
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Machine learning to predict effective reaction rates in 3D porous media from pore structural features. Sci Rep 2022; 12:5486. [PMID: 35361834 PMCID: PMC8971379 DOI: 10.1038/s41598-022-09495-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 03/24/2022] [Indexed: 12/03/2022] Open
Abstract
Large discrepancies between well-mixed reaction rates and effective reactions rates estimated under fluid flow conditions have been a major issue for predicting reactive transport in porous media systems. In this study, we introduce a framework that accurately predicts effective reaction rates directly from pore structural features by combining 3D pore-scale numerical simulations with machine learning (ML). We first perform pore-scale reactive transport simulations with fluid–solid reactions in hundreds of porous media and calculate effective reaction rates from pore-scale concentration fields. We then train a Random Forests model with 11 pore structural features and effective reaction rates to quantify the importance of structural features in determining effective reaction rates. Based on the importance information, we train artificial neural networks with varying number of features and demonstrate that effective reaction rates can be accurately predicted with only three pore structural features, which are specific surface, pore sphericity, and coordination number. Finally, global sensitivity analyses using the ML model elucidates how the three structural features affect effective reaction rates. The proposed framework enables accurate predictions of effective reaction rates directly from a few measurable pore structural features, and the framework is readily applicable to a wide range of applications involving porous media flows.
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Deng H, Fitts JP, Tappero RV, Kim JJ, Peters CA. Acid Erosion of Carbonate Fractures and Accessibility of Arsenic-Bearing Minerals: In Operando Synchrotron-Based Microfluidic Experiment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:12502-12510. [PMID: 32845141 DOI: 10.1021/acs.est.0c03736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Underground flows of acidic fluids through fractured rock can create new porosity and increase accessibility to hazardous trace elements such as arsenic. In this study, we developed a custom microfluidic cell for an in operando synchrotron experiment using X-ray attenuation. The experiment mimics reactive fracture flow by passing an acidic fluid over a surface of mineralogically heterogeneous rock from the Eagle Ford shale. Over 48 h, calcite was preferentially dissolved, forming an altered layer 200-500 μm thick with a porosity of 63-68% and surface area >10× higher than that in the unreacted shale as shown by xCT analyses. Calcite dissolution rate quantified from the attenuation data was 3 × 10-4 mol/m2s and decreased to 3 × 10-5 mol/m2s after 24 h because of increasing diffusion limitations. Erosion of the fracture surface increased access to iron-rich minerals, thereby increasing access to toxic metals such as arsenic. Quantification using XRF and XANES microspectroscopy indicated up to 0.5 wt % of As(-I) in arsenopyrite and 1.2 wt % of As(V) associated with ferrihydrite. This study provides valuable contributions for understanding and predicting fracture alteration and changes to the mobilization potential of hazardous metals and metalloids.
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Affiliation(s)
- Hang Deng
- Energy Geosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Jeffrey P Fitts
- Columbia Electrochemical Energy Center, Columbia University, New York, New York 10027, United States
| | - Ryan V Tappero
- Photon Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Julie J Kim
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Catherine A Peters
- Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, United States
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Mineral Fabric as a Hidden Variable in Fracture Formation in Layered Media. Sci Rep 2020; 10:2260. [PMID: 32041985 PMCID: PMC7010730 DOI: 10.1038/s41598-020-58793-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 01/21/2020] [Indexed: 11/21/2022] Open
Abstract
Two longstanding goals in subsurface science are to induce fractures with a desired geometry and to adaptively control the interstitial geometry of existing fractures in response to changing subsurface conditions. Here, we demonstrate that microscopic mineral fabric and structure interact with macroscopic strain fields to generate emergent meso-scale geometries of induced fractures. These geometries define preferential directions of flow. Using additively manufactured rock, we demonstrate that highly conductive flow paths can be formed in tensile fractures by creating corrugated surfaces. Generation, suppression and enhancement of corrugations depend on the relative orientation between mineral fabric and layering. These insights into the role of micro-scale structure on macro-scale flow provide a new method for designing subsurface strategies to maximize potential production or to inhibit flow.
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Fazeli H, Patel RA, Ellis BR, Hellevang H. Three-Dimensional Pore-Scale Modeling of Fracture Evolution in Heterogeneous Carbonate Caprock Subjected to CO 2-Enriched Brine. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:4630-4639. [PMID: 30945855 DOI: 10.1021/acs.est.8b05653] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Fractures in caprocks overlying CO2 storage reservoirs can adversely affect the sealing capacity of the rocks. Interactions between acidified fluid and minerals with different reactivities along a fracture pathway can affect the chemically induced changes in hydrodynamic properties of fractures. To study porosity and permeability evolution of small-scale (millimeter scale) fractures, a three-dimensional pore-scale reactive transport model based on the lattice Boltzmann method has been developed. The model simulates the evolution of two different fractured carbonate-rich caprock samples subjected to a flow of CO2-rich brine. The results show that the existence of nonreactive minerals along the flow path can restrict the increase in permeability and the cubic law used to relate porosity and permeability in monomineral fractured systems is therefore not valid in multimineral systems. Moreover, the injection of CO2-acidified brine at high rates resulted in a more permeable fractured media in comparison to the case with lower injection rates. The overall rate of calcite dissolution along the fracture decreased over time, confirming similar observations from previous continuum scale models. The presented 3D pore-scale model can be used to provide inputs for continuum scale models, such as improved porosity-permeability relationships for heterogeneous rocks, and also to investigate other reactive transport processes in the context of CO2 leakage in fractured seals.
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Affiliation(s)
- Hossein Fazeli
- Department of Geosciences , University of Oslo , Pb. 1047, Blindern, Oslo , Norway
| | - Ravi A Patel
- Laboratory for waste management (LES) , Paul Scherrer Institute , CH-5232 Villigen-PSI , Switzerland
| | - Brian R Ellis
- Department of Civil and Environmental Engineering , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Helge Hellevang
- Department of Geosciences , University of Oslo , Pb. 1047, Blindern, Oslo , Norway
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