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Journal articleJackson MD, Regnier G, Staffell I, 2024,
Aquifer Thermal Energy Storage for low carbon heating and cooling in the United Kingdom: current status and future prospects
, Applied Energy, Vol: 376, ISSN: 0306-2619Aquifer Thermal Energy Storage (ATES) is an underground thermal energy storage technology that provideslarge capacity (of order MW𝑡ℎ to 10s MW𝑡ℎ), low carbon heating and cooling to large buildings and buildingcomplexes, or district heating/cooling networks. The technology operates through seasonal capture, storageand re-use of thermal energy in shallow aquifers. ATES could make a significant contribution to decarbonisingUK heating and cooling, but uptake is currently very low: eleven low temperature (LT-ATES) systems currentlyoperating in the UK meet <0.01% of the UK’s heating and <0.5% of cooling demand. The WandsworthRiverside Quarter development in London is analysed as a successful UK case study. The UK has large potentialfor widespread deployment of LT-ATES, due to its seasonal climate and the wide availability of suitable aquifersco-located with urban centres of high heating and cooling demand. ATES could supply ca. 61% of UK heatingdemand, and ca. 79% of cooling demand with a 13%–41% reduction in carbon emissions for heating, and70%–94% reduction for cooling, compared to equivalent ground- or air-sourced heat pump systems. However,problems with design and operation in some UK systems have caused sub-optimal performance. The UK canbenefit from experience of both successful and unsuccessful deployments but these need to be more widelyreported. Raising awareness, developing policies to encourage uptake, streamlining regulations and developingexpertise are essential to unlock the potential of ATES technology in the UK, which requires engagement withpolicymakers, regulators, industry stakeholders and the general public.
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Journal articleAl Kubaisy J, Salinas P, Jackson MD, 2024,
A single mesh approximation for modeling multiphase flow in heterogeneous porous media
, Journal of Computational Physics, Vol: 513, ISSN: 0021-9991The control volume finite element (CVFE) approach is based on the discretization of primary flow and transport unknowns on two different meshes. The element mesh, used to represent the physical properties of the medium, differs from the control volume mesh necessary to ensure a mass conservative solution. The inherent two mesh feature of the CVFE approximation introduces inconsistency in the transport solution due to the averaging of physical and computed quantities between neighboring elements in the mesh. In this work, we present a consistent approach for modeling multiphase flow and transport in heterogeneous porous media. The approach is applied in the CVFE framework by enabling the discretization of primary unknowns on a single mesh. We combine the discretization of an element-wise, discontinuous pressure approximation with a first-order, discontinuous velocity approximation to resolve the elliptic or parabolic flow problem. The effectiveness of the formulation is achieved by exploiting the same finite element mesh as the flow problem, when updating the saturation solution. This direct mapping between the flow and transport mesh is simple yet effective for establishing a consistent solution in addition to circumventing the non-physical mass leakage exhibited in the classical CVFE method. We describe the interface approximations and the discontinuous terms needed for consistent solutions. The method is well suited to model flow in complex geometrical subsurface domains and is shown to be numerically stable while providing locally and globally mass conservative solutions. We apply the approach to several domains with complex geometrical features to emphasize the superiority of the approximation over conventional methods. The analysis shows over two orders of magnitude reduction in solution error compared to the classical CVFE. The new formulation effectively captures accurate transport solutions, even in the presence of varying material properties, without the ne
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Journal articlePrince K, Laya JC, Budd D, et al., 2024,
Dolomite occurrence within drift deposits, Maldives archipelago
, Sedimentary Geology, Vol: 470, ISSN: 0037-0738Considerable attention has been dedicated to the sedimentological processes associated with carbonate drift and contourite deposits, but a noticeable gap exists in the understanding of the diagenetic aspects of those deposits, especially dolomitization. This study presents an examination of dolomites from Middle to Late Miocene drift deposits collected during IODP Expedition 359 to the Maldives archipelago. Multiple geochemical parameters and petrographic analysis are used to explore the potential role of closed versus open system dolomitization in the two oldest drift sequences, which are overlain by a multimillion year-long hiatus. Overall, dolomite abundance is variable, but 50 % to nearly 100 % in a 30 m thick interval below the unconformity surface at one of the examined sites. The dolomite in the study interval consists of very fine-to-fine-sized crystalline dolomite cements and mimetically replaced dolomite grains. All dolomite is non-stoichiometric (mean 42.7 ± 2.0 mol% MgCO3) and mostly poorly ordered. Geochemical attributes include relatively invariant δ13C (+1.3 ‰ to +1.7 ‰ VPDB) and relatively high Sr concentrations in dolomite cements (mean 505 ppm) and dolomitized grains (mean 784 ppm). δ18O values and the constraints of burial histories indicate dolomitization in normal marine seawater at burial depths of 0 to 300 m and temperatures of ∼10 °C–14 °C below an ocean water column 100 to 400 m deep. Sr-isotope ages suggest dolomitization of the most extensively dolomitized interval below the unconformity occurred between 12.3 Ma and 6.7 Ma. Overall, the geochemical data and previously published δ34SCAS data suggest a closed, diffusion-dominated system created most of the dolomite. However, the youngest dolomite's age and bulk rock Sr isotope ages of calcitic rocks at the base of the drift deposits can only be explained by the advective flux of seawater through all the drift deposits. Furthermore, the
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Journal articleHossain S, Hampson G, Jacquemyn C, et al., 2024,
Permeability characterisation of sedimentological facies in the Bunter Sandstone Formation, Endurance CO2 storage site, offshore UK
, International Journal of Greenhouse Gas Control, Vol: 135, ISSN: 1750-5836Permeability variations due to sedimentological heterogeneity are important in controlling CO2 migration pathways, CO2 plume dynamics, and stratigraphic, capillary and dissolution trapping of CO2 in subsurface storage units and complexes. Thus, knowing these parameters is crucial to developing a CO2 injection strategy that maximizes storage and trapping efficiency. In this study we analyzed the sedimentological and permeability heterogeneity of the Bunter Sandstone Formation at the Endurance CO2 storage site, offshore UK, through integrated facies analysis, minipermeameter measurements, and thin section analysis. Detailed core logging and outcrop analysis were performed to identify facies and related heterogeneities. Twelve lithofacies have been identified in cores. By analyzing the stacking patterns of the facies, three facies associations and three architectural elements were identified in cores and outcrop analogues, respectively. Heterogeneities occur at all the scales ranging from mm-scale laminae to 10′s m-scale architectural elements.Permeability variations at outcrop and in core are closely related to sedimentological heterogeneities. Minipermeameter and core plug permeability data show up to three orders of magnitude variation across the facies. Cross-bedded (Sp, St, Sl, Spmc) and structureless (Sm) sandstones are the most permeable (4–5400 mD) facies, whereas pebbly conglomerates (Gmg) and laminated mudstones (Fl) are least permeable (0.18–89 mD) facies. Mottled and deformed sandstone (Smd) and crinkly laminated sandstone (Sc) have highly variable permeability (0.69–480 mD). Minipermeameter data reveal permeability varies by a factor of five at centimeter scale within planar cross-bedded (Sp), trough cross-bedded (St) and planar bedded sandstone (Sh) sandstone facies, while planar cross-bedded sandstone with mud clasts along foresets (Spmc) exhibit permeability variation up to a factor of four. Petrographic analysis of thin sections
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Journal articleBooth CA, Jackson MD, Sparks RSJ, et al., 2024,
Source reservoir controls on the size, frequency and compositionof large-scale volcanic eruptions
, Science Advances, Vol: 10, ISSN: 2375-2548Large-scale, explosive volcanic eruptions are one of the Earth’s most hazardous natural phenomena. We demonstrate that their size, frequency, and composition can be explained by processes in long-lived, high-crystallinity source reservoirs that control the episodic creation of large volumes of eruptible silicic magma and its delivery to the subvolcanic chamber where it is stored before eruption. Melt percolates upward through the reservoir and accumulates a large volume of low-crystallinity silicic magma which remains trapped until buoyancy causes magma-driven fractures to propagate into the overlying crust, allowing rapid magma transfer from the reservoir into the chamber. Ongoing melt percolation in the reservoir accumulates a new magma layer and the process repeats. Our results suggest that buoyancy, rather than crystallinity, is the key control on magma delivery from the source reservoir. They identify an optimum reservoir size for the largest silicic eruptions that is consistent with data from natural systems and explain why larger magnitude eruptions are not observed on Earth.
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Journal articleStemmle R, Hanna R, Menberg K, et al., 2024,
Policies for aquifer thermal energy storage: international comparison, barriers and recommendations
, Clean Technologies and Environmental Policy, ISSN: 1618-954XAquifer thermal energy storage (ATES) represents a promising solution for heating and cooling, offering lower greenhouse gas emissions and primary energy consumption than conventional technologies. Despite these benefits and the widespread availability of suitable aquifers, ATES has yet to see widespread utilisation, with uptake highly concentrated in select countries (Netherlands, Belgium, Sweden and Denmark). Beyond technical and hydrogeological feasibility, appropriate national policies are paramount in driving ATES deployment. This study provides an international comparison of ATES policies, highlighting best practices and revealing where measures are missing. It sources insights from a survey of experts across academia, industry and governmental bodies in 30 countries, complemented by semi-structured expert interviews. The study reveals significant differences in the existence and strength of supportive policy environments between countries with different ATES market maturity. A mere 33% of all survey respondents stated that there are policies designed to support ATES utilisation in their respective countries, while the existence of laws and regulations governing ATES was confirmed by 56% of the respondents. The interviews provide details on creating supportive environments (e.g. through facilitators like pre-existing groundwater technology use and building energy efficiency standards) and further barriers to ATES deployment. Ten recommendations for ATES policies are derived to address the following areas: legislative and regulatory issues, raising public awareness, ATES’ role in local energy transitions, and social engagement. This work aims to steer global policy towards better harnessing the potential of ATES to decarbonise buildings.
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Journal articleRowan TSL, Karantoni VA, Butler AP, et al., 2023,
3D-printed Ag-AgCl electrodes for laboratory measurements of self-potential
, GEOSCIENTIFIC INSTRUMENTATION METHODS AND DATA SYSTEMS, Vol: 12, Pages: 259-270, ISSN: 2193-0856 -
Journal articleCollini H, Jackson MD, 2023,
Zeta potential of crude oil in aqueous solution
, Advances in Colloid and Interface Science, Vol: 320, ISSN: 0001-8686Despite the broad range of interest and applications, controls on the surface charge of crude oil in aqueous solution remain poorly understood. The primary data source to understand the surface charge on crude oil comprises measurements of zeta potential on individual drops or emulsions obtained using the electrophoretic method (EPM). Here we (i) collate and review previous measurements of zeta potential on crude oil, (ii) compare and contrast the results, and (iii) report new measurements of zeta potential on crude oil wetting films and layers relevant to oil-saturated porous media, obtained using the streaming potential method (SPM).Results show that the zeta potential depends on electrolyte pH and the concentration of divalent ions Ca2+ and Mg2+. Lower pH and higher concentration of these divalent ions yields more positive zeta potential. The isoelectric point (IEP) in simple NaCl electrolytes lies in the pH range 3–5. The IEP in simple CaCl2 and MgCl2 electrolytes can be expressed as pCa or pMg, respectively, and lies in the range 0–1. Close to the IEP, the zeta potential varies linearly with pH, pCa or pMg, suggesting simple Nernstian behaviour of the crude oil surface. The sensitivity of the zeta potential to pH, pCa and pMg decreases with increasing total ionic strength. The impact of pH, pCa and pMg on zeta potential varies significantly across different crude oils and differs from non-polar hydrocarbons. The potential for other multivalent ions to modify crude oil zeta potential has not been tested. Data for crude oil wetting films and layers, obtained using the SPM and strongly oil-wet porous substrates in which the solid surfaces are coated with the crude oil of interest, are comparable to those obtained using emulsions and the EPM, suggesting that the controls on zeta potential on crude oil are the same irrespective of whether the oil forms droplets or wetting layers.The literature data reviewed here, along with new measured data, provide imp
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Book chapterAlshakri J, Hampson GJ, Jacquemyn C, et al., 2023,
A screening assessment of the impact of sedimentological heterogeneity on CO2 migration and stratigraphic-baffling potential: Sherwood and Bunter Sandstones, UK
, Enabling Secure Subsurface Storage in Future Energy Systems, Publisher: Geological Society of London, Pages: 245-266We use a combination of experimental design, sketch-based reservoir modelling, and flow diagnostics to rapidly screen the impact of sedimentological heterogeneities that constitute baffles and barriers on CO2 migration in depleted hydrocarbon reservoirs and saline aquifers of the Sherwood Sandstone Group and Bunter Sandstone Formation, UK. These storage units consist of fluvial sandstones with subordinate aeolian sandstones, floodplain and sabkha heteroliths, and lacustrine mudstones. The predominant control on effective horizontal permeability is the lateral continuity of aeolian-sandstone intervals. Effective vertical permeability is controlled by the lateral extent, thickness and abundance of lacustrine-mudstone layers and aeolian-sandstone layers, and the mean lateral extent and mean vertical spacing of carbonate-cemented basal channel lags in fluvial facies-association layers. The baffling effect on CO2 migration and retention is approximated by the pore volume injected at breakthrough time, which is controlled largely by three heterogeneities, in order of decreasing impact: (1) the lateral continuity of aeolian-sandstone intervals; (2) the lateral extent of lacustrine-mudstone layers, and (3) the thickness and abundance of fluvial-sandstone, aeolian-sandstone, floodplain-and-sabkha-heterolith and lacustrine-mudstone layers. Future effort should be focussed on characterising these three heterogeneities as a precursor for later capillary, dissolution and mineral trapping.
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Journal articleRegnier G, Salinas P, Jackson MD, 2023,
Predicting the risk of saltwater contamination of freshwater aquifers during aquifer thermal energy storage
, Hydrogeology Journal, Vol: 31, Pages: 1067-1082, ISSN: 1431-2174Aquifer thermal energy storage (ATES) is an underground thermal energy storage technology with a large potential to decarbonise the heating and cooling of buildings. ATES installations typically store thermal energy in aquifers that are also exploited for potable water, so a major consideration during development is ensuring that system operation will not lead to groundwater pollution. In this study, the risk of contamination due to upconing of a shallow freshwater/saltwater interface during ATES operation is investigated. Fluid fow, and heat and salt (chloride ion) transport are simulated in a homogene ous aquifer during ATES operation via a well doublet. The impact of geological, hydrological and operational parameters is investigated in a sensitivity analysis. Two new dimensionless numbers are proposed to characterise salt upconing and redistribution during ATES operation and provide a close match to simulated concentrations: CR,w characterises the con tamination risk at the ATES installation, and CR,d characterises the risk at locations downstream of the ATES installation with respect to background groundwater fow. ATES systems with CR,w and CR,d < 10 introduce low risk of contamination in a homogenous aquifer, with chloride concentration at, and downstream of, the ATES system, remaining below the World Health Organisation’s advised limit. ATES installations with CR,w and CR,d > 10 cause a rapid increase in aquifer chloride concentration. The results are used to estimate an exclusion distance beyond which ATES system operation will not cause contamination in a homogenous aquifer. The dimensionless parameters proposed allow rapid assessment of the potential for saltwater contamination during ATES operation.
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Journal articlePetrovskyy D, Jacquemyn C, Geiger S, et al., 2023,
Rapid flow diagnostics for prototyping of reservoir concepts and models for subsurface CO2 storage
, International Journal of Greenhouse Gas Control, Vol: 124, Pages: 1-16, ISSN: 1750-5836Sketch-based interface and modelling is an approach to reservoir modelling that allows rapid and intuitive creation of 3D reservoir models to test and evaluate geological concepts and hypotheses and thus explore the impact of geological uncertainty on reservoir behaviour. A key advantage of such modelling is the quick creation and quantitative evaluation of reservoir model prototypes. Flow diagnostics capture key aspects of reservoir flow behaviour under simplified physical conditions that enable the rapid solution of the governing equations, and are essential for such quantitative evaluation. In this paper, we demonstrate a novel and highly efficient implementation of a flow diagnostics framework, illustrated with applications to geological storage of CO2. Our implementation permits ‘on-the-fly’ estimation of the key reservoir properties that control CO2 migration and storage during the active injection period when viscous forces dominate. The results substantially improve the efficiency of traditional reservoir modelling and simulation workflows by highlighting key reservoir uncertainties that need to be evaluated in subsequent full-physics reservoir simulations that account for the complex interplay of viscous, gravity, and capillary forces.The methods are implemented in the open-source Rapid Reservoir Modelling software, which includes a simple to use graphical user interface with no steep learning curve. We present proof-of-concept studies of the new flow diagnostics implementation to investigate the CO2 storage potential of sketched 3D models of shallow marine sandstone tongues and deep water slope channels.
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Journal articleAl Kubaisy J, Salinas P, Jackson MD, 2023,
A hybrid pressure approximation in the control volume finite element method for multiphase flow and transport in heterogeneous porous media
, Journal of Computational Physics, Vol: 475, ISSN: 0021-9991We present a new hybrid pressure formulation applied to the control volume finite element (CVFE) method to model multiphase flow and transport in highly heterogeneous porous media. The formulation effectively captures sharp saturation changes in the presence of discontinuous material properties by employing a discontinuous pressure approximation at material interfaces. The heterogeneous porous medium is divided into sub-domains within which material properties are uniform or smoothly varying. By construction, the resultant control volume dual mesh is restricted within a sub-domain. The artificial mass leakage across material property boundaries observed in classical CVFE methods is therefore circumvented. The approach applies the robust continuous pressure approximation in the rest of the computational domain; the discontinuous approximation is applied only at the sub-domain boundaries. The discontinuous parameters necessary to achieve mass conservative solutions, locally and globally, are described. We demonstrate the accuracy and efficiency of the new approach by comparison with the classical continuous CVFE method on various examples of heterogeneous domains as well as establishing the convergence of the numerical method. The proposed hybrid formulation significantly outperforms the accuracy and efficiency of classical CVFE methods that use the same order of approximation for modeling multiphase flow in heterogeneous porous media.
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Conference paperJacquemyn C, Hossain S, Jackson WA, et al., 2023,
Sketch-based modelling with flow diagnostics: Prototyping geomodels for better resource modelling decisions
, Pages: 3687-3691Sketch-based modelling with flow diagnostics provides a prototyping approach to quickly build geomodels and generate quantitative results to evaluate volumetrics and flow behaviour. This approach allows users to rapidly test the sensitivity of model outputs to different geological concepts and uncertain parameters, and informs selection of geological concepts, scales and resolutions to be investigated in more detailed models. Rapid Reservoir Modelling (RRM) is a sketch-based modelling tool with an intuitive interface that allows users to rapidly sketch geological models in 3D. Geological models that capture the essence of heterogeneity of interest and related uncertainty can be created within minutes. Flow diagnostics then instantly computes key indicators of predicted flow and storage behaviour within seconds. Here we apply the prototyping approach to three aspects of geoenergy modelling: (1) scenario screening to identify heterogeneities with the most impact; (2) use of mini-models and hierarchical models to derive effective properties; and (3) training of geoscientists and engineers to investigate the impact of geological interpretations on storage volumes and connectivity. Geomodels addressing all three aspects are constructed and analysed quickly, using simple, geologically intuitive workflows that do not require prior geomodelling expertise.
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Conference paperBaird K, Geiger S, Arnold D, et al., 2023,
Assessing the impact of hierarchical geological heterogeneities on geothermal energy production
, Pages: 568-572Energy derived from geothermal systems is essential to the energy transition. Inherent geological and a lack of data requires the use of computer-driven modelling and simulation to aid decision-making. To make sound decisions, many reservoir models that encapsulate different geological scenarios should be analysed such that the impact of geological uncertainty on geothermal energy production can be evaluated adequately. Current geomodelling workflows, however, are too time consuming to build and explore different contrasting geological scenarios at various scales. In this study we used the open-source Rapid Reservoir Modelling (RRM) software to design different geological scenarios of a shallow marine succession hosting a potential geothermal reservoir and analyse how multi-scale geological features impact reservoir flow. RRM allows users to quickly create and explore realistic 3D geological models from intuitive 2D sketches. Models arecreated in minutes while flow diagnostics allow us to analyse fluid-flow behavior in real-time. Models are then imported into commercial reservoir simulation packages to investigate the effect of heterogeneity and scale on geothermal energy production. We show how we can quickly evaluate how different scales of heterogeneity impact geothermal production estimates and which heterogeneities must be represented in reservoir models to obtain reliable results about the possible reservoir behaviours.
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Journal articleHu H, Jackson MD, Blundy J, 2022,
Melting, compaction and reactive flow: controls on melt fraction and composition change in crustal mush reservoirs
, Journal of Petrology, Vol: 63, ISSN: 0022-3530Changes in melt fraction and local bulk composition in high-crystallinity, crustal mush reservoirs are essential to produce the large volumes of low-crystallinity, silicic magma that are emplaced to form plutons, or erupted to surface. Heating (and cooling) is well understood and widely invoked in driving melt fraction change, but does not cause chemical differentiation because there is no separation of melt and crystals. Fractional crystallisation at high melt fraction is widely assumed to explain differentiation, but is inconsistent with the evidence that large-scale, long-term magma storage and evolution occurs in high-crystallinity mush reservoirs. Compaction has been suggested to explain melt fraction change and differentiation at low melt fraction, but compaction (and decompaction) causes simple unmixing (and mixing) of melt and solid crystals: to produce very refractory bulk composition by compaction, melt fraction must be driven down to very low values. Yet microstructural evidence demonstrating widespread compaction in crustal mush reservoirs at low melt fraction is lacking. Here we show that melt fraction change can be expressed in terms of heating/cooling and compaction, plus an additional term that we call ‘reactive flow’. Similarly, composition change can be expressed in terms of compaction and reactive flow. Reactive flow changes the local bulk composition, which causes ‘chemical’ melting (dissolution) and freezing (precipitation), distinct from ‘thermal’ melting/freezing caused by changes in enthalpy. We use numerical modelling to show that the contributions of compaction and reactive flow in a crustal magma reservoir are similar in magnitude. However, reactive flow opposes melt fraction and composition changes caused by compaction when compaction occurs in a temperature gradient that increases upwards at, for example, the base of a sill intrusion, or decompaction occurs in a temperature gradient that decreases upwa
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Journal articleJackson WA, Hampson GJ, Jacquemyn C, et al., 2022,
A screening assessment of the impact of sedimentological heterogeneity on CO2 migration and stratigraphic-baffling potential: Johansen and Cook formations, Northern Lights project, offshore Norway
, International Journal of Greenhouse Gas Control, Vol: 120, Pages: 1-23, ISSN: 1750-5836We use a method combining experimental design, sketch-based reservoir modelling, and single-phase flow diagnostics to rapidly screen the impact of sedimentological heterogeneities that constitute baffles and barriers to CO2 migration in the Johansen and Cook formations at the Northern Lights CO2 storage site. The types and spatial organisation of sedimentological heterogeneities in the wave-dominated deltaic sandstones of the Johansen-Cook storage unit are constrained using core data from the 31/5-7 (Eos) well, previous interpretations of seismic data and regional well-log correlations, and outcrop and subsurface analogues. Delta planform geometry, clinoform dip, and facies-association interfingering extent along clinoforms control: (1) the distribution and connectivity of high-permeability medial and proximal delta-front sandstones, (2) effective horizontal and vertical permeability characteristics of the storage unit, and (3) pore volumes injected at breakthrough time (which approximates the efficiency of stratigraphic baffling). In addition, the lateral continuity of carbonate-cemented concretionary layers along transgressive surfaces impacts effective vertical permeability, and bioturbation intensity impacts effective horizontal and vertical permeability. The combined effects of these and other heterogeneities are also influential. Our results suggest that the baffling effect on CO2 migration and retention of sedimentological heterogeneity is an important precursor for later capillary, dissolution and mineral trapping.
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Journal articleAlarouj M, Jackson MD, 2022,
Experimental measurement of the exclusion-diffusion potential in sandstone and shaly sand samples at full and partial water saturation
, GEOPHYSICS, Vol: 87, Pages: M235-M246, ISSN: 0016-8033 -
Journal articleBahlali ML, Salinas P, Jackson MD, 2022,
Efficient numerical simulation of density-driven flows: application to the 2-and 3-D Elder problem
, Water Resources Research, Vol: 58, ISSN: 0043-1397Modeling density-driven flow in porous media is challenging due to the nonlinear couplingbetween flow and transport equations, the large domains of interest and the wide range of time and spacescales involved. Solving this type of problem numerically using a fixed mesh can be prohibitively expensive.Here, we apply a dynamic mesh optimization (DMO) technique along with a control-volume-finite elementmethod to simulate density-driven flows. DMO allows the mesh resolution and geometry to vary during asimulation to minimize an error metric for one or more solution fields of interest, refining where needed andcoarsening elsewhere. We apply DMO to the Elder problem for several Rayleigh numbers. It is demonstratedthat DMO accurately reproduces the unique two-dimensional (2D) solutions for low Rayleigh number casesat significantly lower computational cost compared to an equivalent fixed mesh, with speedup of order ×16.For unstable, high Rayleigh number 2D cases, multiple steady-state fingering solutions exist and are allcaptured by our approach with high accuracy and significantly reduced computational cost, with speedup oforder ×6. Velocity-dependent dispersion is shown to have a small impact on the 2D numerical solutions. Thelower computational cost of simulations using DMO allows extension of the high Rayleigh number case to athree dimensional (3D) configuration. We demonstrate new 3D fingering patterns that have not been observedpreviously. Early time, transient 3D patterns represent combinations of the previously observed, steady-state 2Dsolutions, but all evolve to a single, steady-state finger in the late time limit.
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Journal articleHamzehloo A, Bahlali ML, Salinas P, et al., 2022,
Modelling saline intrusion using dynamic mesh optimization with parallel processing
, Advances in Water Resources, Vol: 164, ISSN: 0309-1708Saline intrusion (SI) in coastal aquifers is a global problem with the potential to contaminate groundwaterused by over a billion people. Numerical modelling of SI in coastal aquifers is a key tool for risk assessment,aquifer management and resource regulation, but is extremely challenging because the mixing zone across thesaline front is often very narrow, extending over metres or 10’s metres, yet the saline front itself may extendlaterally over a large (i.e. many km) three-dimensional (3D) domain. Moreover, the aquifer may be highlyheterogeneous, further complicating the movement and geometry of the front. We test here the use of dynamicmesh optimization (DMO) in a parallel computational framework to simulate SI with higher accuracy and lowercomputational cost compared to fixed-mesh approaches. The framework uses a double control-volume-finite element (DCVFE) method and is implemented in the open-source Imperial College Finite Element ReservoirSimulaTor (IC-FERST), but could be implemented in other FE-based simulators. We confirm accuracy andconvergence using test cases based on the classic ’Henry’ SI problem, demonstrating that solutions obtainedusing DMO require significantly fewer elements and therefore have much lower computational cost comparedto equivalent fixed mesh solutions. We apply the framework to a realistic 3D case study simulating salineintrusion in a heterogeneous chalk aquifer, demonstrating simulation speed-up in excess of 120×. We suggestthat parallelized DMO offers significant advantages over existing methods to simulate SI.
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Journal articleRegnier G, Salinas P, Jacquemyn C, et al., 2022,
Numerical simulation of aquifer thermal energy storage using surface-based geologic modelling and dynamic mesh optimisation
, Hydrogeology Journal, Vol: 30, Pages: 1179-1198, ISSN: 1431-2174Aquifer thermal energy storage (ATES) has significant potential to provide largescale seasonal cooling and heating in the built environment, offering a low-carbon alternative to fossil fuels. To deliver safe and sustainable ATES deployments, accurate numerical modelling tools must be used to predict flow and heat transport in the targeted aquifers. This paper presents a simulation methodology for ATES based on surface-based geologic modelling (SBGM) and dynamic mesh optimisation (DMO). DMO has been previously applied in other fields of computational fluid dynamics to reduce the cost of numerical simulations. DMO allows the resolution of the mesh to vary during a simulation to satisfy a user-defined solution precision for selected fields, refining where the solution fields are complex and coarsening elsewhere. SBGM allows accurate representation of complex geological heterogeneity and efficient application of DMO. The paper reports the first systematic convergence study for ATES simulations, and demonstrates the application of these methods in two ATES scenarios: a homogeneous aquifer, and a realistic heterogeneous fluvial aquifer containing meandering, channelised sand bodies separated by mudstones. It is demonstrated that DMO reduces the required number of mesh elements by a factor of up to 22 and simulation time by a factor of up to 15, whilst maintaining the same accuracy as an equivalent fixed mesh. DMO offers significant potential to reduce the computational cost of ATES simulations in both homogeneous and heterogeneous aquifers.
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