Reactive Transport of CO2 in Saline Aquifers with implicit geomechanical analysis

Geological storage of CO2 in saline aquifers is a promising way to reduce the concentration of the greenhouse gas in the atmosphere. Injection of CO2 will, however, lead to dissolution of minerals in regions of lowered pH and precipitation of minerals from transported ions in regions of higher pH. The geomechanical implications of these changes on the stability of the reservoir are of crucial importance in the evaluation of potential injection reservoirs. The possible injection rate for given over-pressures of the injected CO2 depends on the porosity and permeability of the rock matrix in the vicinity of the injection well. Local fracturing in this region can be a tool for increasing the injection flow rate but a geomechanical analysis will be needed in order to make sure that this fracturing will not affect the geomechanical stability outside this limited region to a significant degree. This paper presents a new rewritten version of RetrasoCodeBright (RCB) which have been extended to simulations of CO2 storage in saline aquifers. An advantage of this code compared to other codes is the implicit geo-mechanical module. The code has been rewritten to account for non-ideal gas through corrections of gas density and gas solubility in all transport terms. Newton–Raphson method used to solve the flow and mechanics in RCB has been improved so as to improve convergence even under high gas injecting pressures. A 2D hydro-chemical-mechanical problem is used to illustrate the modified RCB code.publishedVersio

Modeling Heat Transport in Systems of Hydrate-Filled Sediments Using Residual Thermodynamics and Classical Nucleation Theory

As in any other phase transition, hydrate phase transition kinetics involves an implicit coupling of phase transition thermodynamic control and the associated dynamics of mass and heat transport. This work provides a brief overview of certain selected hydrate film growth models with an emphasis on analyzing the hydrate phase transition dynamics. Our analysis is based on the fundamental properties of hydrate and hydrate/liquid water interfaces derived from molecular modeling. We demonstrate that hydrate phase transitions involving water-dominated phases are characterized by heat transport several orders of magnitude faster than mass transport, strongly suggesting that any hydrate phase transition kinetic models based on heat transport will be entirely incorrect as far as thermodynamics is concerned. We therefore propose that theoretical studies focusing on hydrate nucleation and growth should be based on concepts that incorporate all the relevant transport properties. We also illustrate this point using the example of a fairly simplistic kinetic model, that of classical nucleation theory (CNT), modified to incorporate new models for mass transport across water/hydrate interfaces. A novel and consistent model suitable for the calculation of enthalpies is also discussed and appropriate calculations for pure components and relevant mixtures of carbon dioxide, methane, and nitrogen are demonstrated. This residual thermodynamic model for hydrate is consistent with the free energy model for hydrate and ensures that our revised CNT model is thermodynamically harmonious.publishedVersio

Phase field theory of crystal nucleation in hard sphere liquid

The phase field theory of crystal nucleation described in [L. Granasy, T. Borzsonyi, T. Pusztai, Phys. Rev. Lett. 88, 206105 (2002)] is applied for nucleation in hard--sphere liquids. The exact thermodynamics from molecular dynamics is used. The interface thickness for phase field is evaluated from the cross--interfacial variation of the height of the singlet density peaks. The model parameters are fixed in equilibrium so that the free energy and thickness of the (111), (110), and (100) interfaces from molecular dynamics are recovered. The density profiles predicted without adjustable parameters are in a good agreement with the filtered densities from the simulations. Assuming spherical symmetry, we evaluate the height of the nucleation barrier and the Tolman length without adjustable parameters. The barrier heights calculated with the properties of the (111) and (110) interfaces envelope the Monte Carlo results, while those obtained with the average interface properties fall very close to the exact values. In contrast, the classical sharp interface model considerably underestimates the height of the nucleation barrier. We find that the Tolman length is positive for small clusters and decreases with increasing size, a trend consistent with computer simulations.Comment: 7 pages, 7 figure

Effects of salinity on hydrate stability and implications for storage of CO2 in natural gas hydrate reservoirs

The win-win situation of CO2 storage in natural gas hydrate reservoirs is attractive for several reasons in addition to the associated natural gas production. Since both pure CO2 and pure methane form structure I hydrate there is no expected volume change by replacing the in situ methane with CO2, and there is not net production of associated water which requires extra handling. The geo-mechanical implication of the first of these may be a very important issue since hydrates in unconsolidated sediments are the most promising targets for exploitation of natural gas. The stability of CO2 stored in the form of hydrate is probably one of the safest options today, even though also this option relates to safety of sealing cap-rock or clay layer. The stability of hydrates in a reservoir depends on many factors, including the interactions between minerals, surrounding fluids and hydrate. The natural level of salinity increases with depth in a reservoir. In addition formation of hydrate will lead to increased salinity of the fluids surrounding the formed hydrate. This may lead to liquid pockets of residual aqueous solution with increased salinity as well as very non-uniform hydrate. The latter due to the fact that hydrate composition and stability relates to properties of surrounding fluids. In the work presented here methane hydrates were formed in several sandstone cores. The cores were all partially saturated with brine of different salinities in order to identify the effect salinity has on the fill fraction, the amount of methane per available structural site in hydrates. The results indicate that salinities lower than regular sea water composition has no significant impact on the fill fraction of methane hydrate in porous media. When the salinity surpasses regular sea water composition there is a significant drop in fill fraction. The methane hydrate fill fraction is dominated by total brine salinity rather than brine distribution in the core.publishedVersio

Transport and storage of CO2 in natural gas hydrate reservoirs

Storage of CO2 in natural gas hydrate reservoirs may offer stable long term deposition of a greenhouse gas while benefiting from methane production, without requiring heat. By exposing hydrate to a thermodynamically preferred hydrate former, CO2, the hydrate may be maintained macroscopically in the solid state and retain the stability of the formation. One of the concerns, however, is the flow capacity in such reservoirs. This in turn depends on three factors; 1) thermodynamic destabilization of hydrate in small pores due to capillary effects, 2) the presence of liquid channels separating the hydrate from the mineral surfaces and 3) the connectivity of gas- or liquid filled pores and channels. This paper reports experimental results of CH4- CO2 exchange within sandstone pores and measurements of gas permeability during stages of hydrate growth in sandstone core plugs. Interactions between minerals and surrounding molecules are also discussed. The formation of methane hydrate in porous media was monitored and quantified with magnetic resonance imaging techniques (MRI). Hydrate growth pattern within the porous rock is discussed along with measurements of gas permeability at various hydrate saturations. Gas permeability was measured at steady state flow of methane through the hydrate-bearing core sample. Experiments on CO2 injection in hydrate-bearing sediments was conducted in a similar fashion. By use of MRI and an experimental system designed for precise and stabile pressure and temperature controls flow of methane and CO2 through the sandstone core proved to be possible for hydrate saturations exceeding 60%.publishedVersio

Simulation of hydrate dynamics in reservoirs

Gas hydrates in reservoirs are generally not in thermodynamic equilibrium and there may be several competing phase transitions involving hydrate. Formation of carbon dioxide hydrates during aquifer storage of carbon dioxide involves roughly 10% volume increase compared to groundwater. Dissociation of hydrate towards under saturated fluid phases involves the same level of contraction. Hydrate phase transitions are generally fast (scales of seconds) compared to mineral dissolution and precipitation and it is unlikely that a time shifted explicit coupling to geo mechanical analysis will be able to capture the appropriate dynamic couplings between flow and changes in stress. The need for geo mechanical integrity of the storage site therefore requires a reservoir simulator with an implicit solution of mass flow, heat flow and geo mechanics. And since carbon dioxide involved in hydrate is also involved in different geochemical reactions we propose a scheme where all possible hydrate formation (on water/carbon dioxide interface, from water solution and from carbon dioxide adsorbed on mineral surfaces) as well as all different possible dissociations are treated as pseudo reactions but with kinetics derived from advanced theoretical modelling. The main tools for generating these models have been phase field theory simulations, with thermodynamic properties derived from molecular modelling. The detailed results from these types of simulations provides information on the relative impact of mass transport, heat transport and thermodynamics of the phase transition which enable qualified simplifications for implementation into RCB. The primary step was to study the effect of hydrate growth or dissociation with a certain kinetic rate on the mechanical properties of the reservoir. Details of the simulator, and numerical algorithms, are discussed in detail and some relevant examples are shown

Annual report on health monitoring of wild anadromous salmonids in Norway 2021 - Screening of Atlantic salmon (Salmo salar) postsmolts for viral infections

Havforskningsinstituttet har undersøkt utbredelsen av infeksiøs lakseanemi virus (ILAV) og salmonid alfavirus (SAV, PD-virus) infeksjoner i utvandrende vill atlantisk postsmolt fanget i 2020 i tre fjordsystemer lokalisert i tre akvakultur produksjonsområder (PO3, 5, 12). Fisken ble samlet inn som en del av NALO-programmet i de ytre delene av fjordene; Hardangerfjorden (N = 100), Romsdalsfjorden (N = 100) og Altafjorden (N = 100) ved tråling i perioden mai-juni. SAV ble påvist i én postsmolt fra Hardangerfjorden og ILAV i én smolt fra Altafjorden. Høy Ct-verdi (37,6) i den SAV-positive fisken kan imidlertid tyde på et falskt positivt resultat. ILAV påvisningen var sannsynligvis av den apatogene HPR0-varianten av viruset. Funnene fra den nåværende rapporten indikerer en svært lav forekomst av disse virusene i vill migrerende postsmolt av laks. Disse funnene utfyller og støtter våre tidligere rapporterte data, og kan antyde at utbredelsen av ILAV- eller SAV-infeksjoner i villaks postsmolt ikke er signifikant påvirket av forekomsten av disse infeksjonene i fiskeoppdrett.publishedVersio

Annual report on health monitoring of wild anadromous salmonids in Norway 2022 - Screening of Atlantic salmon (Salmo salar) postsmolts from Boknafjorden, Hardangerfjorden and Romsdalsfjorden for viral infections

The Institute of Marine Research has investigated the prevalence of infectious salmon anaemia virus (ISAV), salmonid alphavirus (SAV, PD-virus), piscine orthoreovirus 1 (PRV-1), piscine myocarditis virus (PMCV) and infectious pancreatic necrosis virus (IPNV) infections in migrating wild Atlantic salmon postsmolts captured in 2021 in three fjord systems located in three aquaculture production areas (PO2, 3 and 5). The fish were collected as part of the national salmon lice monitoring program in the outer parts of Boknafjord (N = 50), Hardangerfjord (N = 57) and Romsdalsfjord (N = 73) by trawling during the period May-June. SAV was detected in 2 postsmolts from Romsdalsfjord. PRV-1 was detected in 11 (6%) of postsmolts (8 from Boknafjord, 1 from Hardangerfjord and 2 from Romsdalsfjord). Low concentrations of PMCV-RNA were detected in 19 (11 %) of postsmolts (13 from Boknafjord and 6 from Romsdalsfjord). ISAV and IPNV were not detected in any of the test fish. Generally, the virus-positive fish had high Ct-values which may indicate very low virus concentrations. The results in the current report showed that migrating postsmolts from fjords had a very low occurrence of virus infections common in Norwegian aquaculture. These findings complement and corroborate our previously reported data and may suggest that prevalence virus infections in wild salmon postsmolts is not significantly influenced by the occurrence of these infections in fish farming.Annual report on health monitoring of wild anadromous salmonids in Norway 2022 - Screening of Atlantic salmon (Salmo salar) postsmolts from Boknafjorden, Hardangerfjorden and Romsdalsfjorden for viral infectionspublishedVersio

Effects of environmental stress on mRNA expression levels of seven genes related to oxidative stress and growth in Atlantic salmon Salmo salar L. of farmed, hybrid and wild origin

Background: Ten generations of domestication selection has caused farmed Atlantic salmon Salmo salar L. to deviate from wild salmon in a range of traits. Each year hundreds of thousands of farmed salmon escape into the wild. Thus, interbreeding between farmed escapees and wild conspecifics represents a significant threat to the genetic integrity of wild salmon populations. In a previous study we demonstrated how domestication has inadvertently selected for reduced responsiveness to stress in farmed salmon. To complement that study, we have evaluated the expression of seven stress-related genes in head kidney of salmon of farmed, hybrid and wild origin exposed to environmentally induced stress. Results: In general, the crowding stressor used to induce environmental stress did not have a strong impact on mRNA expression levels of the seven genes, except for insulin-like growth factor-1 (IGF-1) that was downregulated in the stress treatment relative to the control treatment. mRNA expression levels of glutathione reductase (GR), Cu/Zn superoxide dismutase (Cu/Zn SOD), Mn superoxide dismutase (Mn SOD), glutathione peroxidase (GP) and IGF-1 were affected by genetic origin, thus expressed significantly different between the salmon of farmed, hybrid or wild origin. A positive relationship was detected between body size of wild salmon and mRNA expression level of the IGF-1 gene, in both environments. No such relationship was observed for the hybrid or farmed salmon. Conclusion: Farmed salmon in this study displayed significantly elevated mRNA levels of the IGF-1 gene relative to the wild salmon, in both treatments, while hybrids displayed a non additive pattern of inheritance. As IGF-1 mRNA levels are positively correlated to growth rate, the observed positive relationship between body size and IGF-1 mRNA levels detected in the wild but neither in the farmed nor the hybrid salmon, could indicate that growth selection has increased IGF-1 levels in farmed salmon to the extent that they may not be limiting growth rate.publishedVersio

Annual report on health monitoring of wild anadromous salmonids in Norway 2020 - Screening of wild Atlantic salmon (Salmo salar) postsmolts for viral infections

The Institute of Marine Research has investigated the prevalence of infectious salmon anaemia virus (ISAV) and salmonid alphavirus (SAV, PD-virus) infections in migrating wild Atlantic salmon postsmolts captured in 2019 in three fjord systems located in three aquaculture production areas (PO2-4). These areas have had a sporadic case of ISA and a stable high incidence rate of PD, as well as a very high aquaculture intensity. The fish were collected as part of the national salmon lice monitoring program in the outer parts of the Bokna (N=132), Hardanger (N=110) and Sogne (N=110) fjords by trawling during the period May-June. ISAV was detected in two postsmolts from Hardanger fjord and SAV in one smolt from Sogne fjord. The Ct-value of SAV-positive fish was very high (38.9) which may suggest a false positive result. The findings from the current report indicate a very low prevalence of these viruses in wild migrating postsmolts. These findings complement and corroborate our previously reported data and may suggest that prevalence of ISAV or SAV infections in wild salmon postsmolts are not significantly influenced by the occurrence of these infections in fish farming.publishedVersio