Large scale gas injection test (Lasgit) performed at the Äspö Hard Rock Laboratory: summary report 2007

The deposition hole was closed on the 1st February 2005 signifying the start of the hydration phase. Groundwater inflow through a number of conductive discrete fractures resulted in elevated porewater pressures leading to the formation of conductive channels (piping), the extrusion of bentonite from the hole and the discharge of groundwater to the gallery floor. This problem was addressed by drilling two pressure-relief holes in the surrounding rock mass. Artificial hydration began on the 18th May 2005 after 106 days of testing. Initial attempts to raise porewater pressure in the artificial hydration arrays often resulted in the formation of preferential pathways. These pressure dependent features were not focused in one location but occurred at multiple sites at different times in the test history. These pathways appear to be relatively short lived, closing when water pressure is reduced. It was determined that both pressure relief holes should remain open until the bentonite had generated sufficient swelling pressure to withstand the high water pressure in the system when these holes are closed. Packers were installed into the pressure relief holes on 23rd March 2006 and sections in them closed off over the period to 5th July 2006. There was no repeat of the formation of piping through discrete channels so, on 20th November 2006, pressures to the artificial hydration filters on the canister were increased to 2350 kPa

Consolidation and rebound properties of Opalinus Clay : a long-term, fully drained test

A specimen of Opalinus clay from Mont Terri has been subjected to stress testing over a period of 532 days. Testing was undertaken by changing either (or both) of the axial and confining stresses in sharp steps followed by periods of between 4 and 82 days during which time the specimen was allowed to adjust to the new stress state. In this way, the drained consolidation, creep and rebound behaviour of an Opalinus clay specimen was examined. The test material was subjected to a maximum average effective stress of 38.3 MPa. Volumetric strain data for both volume change and porewater displacement measurements indicate a small inflection in the standard geotechnical plot of void ratio against the logarithm of average effective stress at a value between 20 and 22 MPa. The negative slope of the consolidation curve (α) based on volume change measurements exhibits a general trend of increasing magnitude as effective stress rises. Even though the data do not exhibit the sharp increase in α indicative of classic virgin consolidation behaviour, it would appear that plastic yielding is occurring at an average effective stress below 20 MPa. Analysis of net porewater flow measurements suggest original interstitial fluid was not expelled from the specimen until average effective stress exceeded 20 MPa. Given the data available, an estimate for the preconsolidation stress in the region of 20 to 25 MPa seems reasonable. As effective stress rises the duration of the strain transients lengthen. As the induration state of the mudrock increases, strain traces are characterised by less well-defined transients, indicative of time-dependent plastic yielding at high effective stresses. The volumetric strain data for both volume change and porewater displacement shows similar transient behaviour. These results give an average principal strain ratio of 0.252, suggesting the material is either mechanically anisotropic or behaving as a non-ideal elastic medium. Specific storage values derived from porewater displacement measurements show a general decreasing trend with increasing average effective stress and are in the range 1.5 to 12.5 × 10-6 m-1. Data from volume change measurements are less sensitive to changes in effective stress and are in the range 1.2 to 17.5 × 10-6 m-1. Elastic constants derived for undrained quantities are significantly higher than those for drained conditions by approximately one order of magnitude. Data suggests there is a transition in behaviour centred around an average effective stress of approximately 20 MPa. Analysis of creep curves can be broken down into three distinct responses. The Lemaitre model, as applied to Opalinus clay by Boidy (Boidy et al., 2002), was applied to the current test data. However the published model parameters failed to adequately fit the current data. Minor alteration of these parameters enabled modelling of the longer-term volumetric responses to be undertaken. The Lemaitre model did not predict the initial stage of creep very effectively. A much slower response time was seen in the current data, which was absent in the work by previous researchers. A power-law creep model was established. In general the fit was adequate for the volumetric strain observed, although these data exhibited some noise. In contrast, the fit of the axial strain data was not adequate and even the subdividing of the data into the individual creep stages failed to give an acceptable fit. A combination of power-law for the initial response and Lemaitre for the longer response may achieve a better prediction for this test stage. A numerical simulation was run using the 2-dimensional coupled flow and deformation code STAFAN. Two phases of the testing were modelled separately. During Phase 1, the model was used in an attempt to fit the creep data. A reasonable fit was made to the first step axial strain data, but the extrapolation to later stages showed a progressive deviation from the data. In addition, the model made poor predictions for the radial strain and porewater flow data in all steps. These observations indicate that both the assumptions of linear elasticity and isotropic deformation are probably invalid for this specimen. During the second phase of testing, the axial and confining stresses were raised synchronously in a series of seven 4 MPa steps. In view of the results of the Phase 1 modelling, it was decided to treat each step of Phase 2 as a separate test and to use the model to parameterise the changing state of the specimen. Young’s modulus was significantly lower than those derived from volume and porewater displacement measurements, which can be explained by the over prediction of radial strain due to the simple linear-elastic assumption in the STAFAN model. It has been shown that the linear elastic deformation model is not a good analogue for the behaviour of this specimen. There are clear indications of non-linear responses to stress changes in the data and it seems likely that some form of viscoelastic or viscoplastic model should be adopted. In addition, the axial and radial strain responses would seem to be anisotropic, bringing further complexity to the model that should be employed

The G0 Experiment: Apparatus for Parity-Violating Electron Scattering Measurements at Forward and Backward Angles

In the G0 experiment, performed at Jefferson Lab, the parity-violating elastic scattering of electrons from protons and quasi-elastic scattering from deuterons is measured in order to determine the neutral weak currents of the nucleon. Asymmetries as small as 1 part per million in the scattering of a polarized electron beam are determined using a dedicated apparatus. It consists of specialized beam-monitoring and control systems, a cryogenic hydrogen (or deuterium) target, and a superconducting, toroidal magnetic spectrometer equipped with plastic scintillation and aerogel Cerenkov detectors, as well as fast readout electronics for the measurement of individual events. The overall design and performance of this experimental system is discussed.Comment: Submitted to Nuclear Instruments and Method

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

Introduction: The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures. Methods: In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025. Findings: Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2–6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p5mg/L, OR 3·55 [1·23–11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation. Interpretation: After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification. Funding: UK Research and Innovation and National Institute for Health Research

The Weyburn project : summary report for Task 3.1 : experimental geochemical studies of CO2-porewater-rock interaction

This report describes work undertaken at the British Geological Survey (BGS) that forms part of the international Weyburn Monitoring and Storage Project. This project aims to monitor and predict the behaviour of injected CO2 into the Midale reservoir at the Weyburn oil field in southern Saskatchewan, Canada, using methods that include time-lapse geophysics, modelling its subsurface distribution and migration, and simulating likely chemical interactions with the host rock. This report is a summary of Task 3.1 within the European part of the overall Weyburn project. It aims to provide a brief description of fluid chemical and mineralogical changes occurring in a series of experiments that have been conducted within the Hydrothermal Laboratory of the British Geological Survey. These experiments were undertaken to identify the geochemical changes that would result from the injection of CO2 into the Midale Formations. The experiments utilised samples of actual Midale rocks recovered from boreholes within the Weyburn field, synthetic formation water based upon measured well fluid compositions, and either CO2 or N2 as a pressurising medium. The experiments summarised in this report used actual samples of Midale core material and synthetic porewaters based upon actual measured well fluid compositions. The pressures and temperatures used within the experiments were representative of in-situ conditions (60°C, 150 bar [15 MPa]) and those anticipated near to injection wells (60°C, 250 bar [25 MPa]). As such, the study aims to replicate processes occurring in the deep subsurface at Weyburn as closely as possible, including those conditions that will exist even after oil production and CO2 injection have ceased. Upon reaction with CO2, some dissolution of calcite within the Midale Marly material was identified, though it was relatively minor. By and large, the samples remained relatively unchanged, and significant disruption of the host formation appears not to take place. The Midale Evaporite showed slightly more reaction with CO2 compared to the Midale Marly, though it was still relatively minor. Some dissolution of dolomite and anhydrite was identified, together with minor aluminosilicate mineral dissolution. There was also a small amount of gypsum precipitation. Significant dissolution of the caprock formation appears not to take place. The Midale Vuggy material showed the greatest potential for reaction with CO2. Dissolution was mainly of calcite and anhydrite, but there was also a little aluminosilicate mineral dissolution. Precipitation of gypsum was widespread, with crystals at least 2.5 mm long being observed. Samples of borehole cement underwent carbonation of their outer portions upon exposure to CO2, and this was associated with an apparent reduction in porosity. The monoliths remained intact and appear to have maintained much of their original strength

Large-scale column experiment : study of CO2, porewater, rock reactions and model test case

During underground carbon dioxide (CO2) storage operations in deep reservoirs, the CO2 can be trapped in three ways; - as "free" CO2, most likely as a supercritical phase (physical trapping); - dissolved in formation water (hydrodynamic trapping); - precipitated in carbonate phases such as calcite (mineral trapping). This study focuses on the reactions between CO2, porewater and host rock. The aim of this work was to provide a well-constrained long-term laboratory experiment reacting known quantities of minerals with CO2-rich fluids, in order to try and represent situations where CO2 is being injected into lithologies deep underground. The experimental results can then be used as a test case with which to help validate predictive geochemical computer models. These will help improve our ability to predict the long-term fate of carbon dioxide (CO2) stored underground. The experiment, though complex in terms of equipment, ran for approximately 7.5 months. The reacted material was then examined for mineralogical changes and the collected fluids analysed to provide data on the fate of the dissolved species. Changes were readily observable on the carbonates present in thestarting material, which matches well with the observed trends in the fluid chemistry. However, although changes in silica concentrations were seen in the fluid chemistry no evidence for pitting or etching was noted in the silica bearing phases. Modelling of the experimental systems was performed using the BGS coupled code, PRECIP. As a general conclusion, the model predictions tend to over estimate the degree of reaction compared with the results from the experiment. In particular, some mineral phases (e.g. dawsonite) that are predicted to form in large quantities by the model are not seen at all in the experimental system. The differences between the model predictions and the experimental observations highlight the need for thermodynamic and kinetic data to be available under appropriate conditions (pH, and chemical composition of the fluid as well as temperature, and pressure), as extrapolation or "best guesses" may lead to errors being induced in the predictions. These errors and gaps in the data become obvious when comparing model predictions with experiments which serves to emphasise the importance of having "test cases" with which the models can be validated

Geochemical interactions between supercritical CO2 and the Midale Formation. V : experiments investigating reactions of the Midale Vuggy

This report describes work undertaken at the British Geological Survey (BGS) that forms part of the international IEA Weyburn Carbon Dioxide (CO2) Monitoring and Storage Project. This project aims to monitor and predict the behaviour of injected CO2 into the Midale reservoir at the Weyburn oil field in southern Saskatchewan, Canada, using methods that include; time-lapse geophysics, modelling its subsurface distribution and migration, and simulating likely chemical interactions with the host rock. This report aims to provide a description of fluid chemical and mineralogical changes occurring in a series of experiments that have been conducted within the Hydrothermal Laboratory of the British Geological Survey. These experiments were undertaken to identify what geochemical changes would result from the injection of CO2 into the Midale Vuggy formation. The experiments utilised samples of Midale Vuggy core material from the Weyburn field, synthetic formation water based upon measured well fluid compositions, and either CO2 or N2 as a pressurising medium. The experiments were conducted at 60°C and pressurised to either 150 bar [15 MPa] or 250 bar [25 MPa], using either CO2 or N2. Experiment durations ranged from one week to 6 months. The evolution over time of a selection of solutes was followed. Relative to the N2 ‘baseline’ experiments, it was found that the impact of CO2 was to: - increase the concentrations of Ca, Si and HCO3 - - decrease the concentrations of total S and possibly Sr, and pH values - have little impact on the concentrations of Mg, Mn and Al It is noted that these fluid chemical changes are not dissimilar to those found in the Midale Marly experiments (Rochelle et al., 2003a) All monoliths reacted in CO2-rich synthetic pore waters showed clear evidence of ‘tidemarks’ on their external surfaces, with the area below the water-CO2 interface appearing bleached. After 4 weeks of reaction of the monoliths with CO2, euhedral prismatic gypsum crystals up to 500 µm in length formed below the water line in the CO2 experiment. By 8 weeks reaction the gypsum crystals were at least 2.5 mm long, and at 17 weeks reaction gypsum crystals up to 500 µm long also developed in the baseline N2 experiment. In addition, most calcite and anhydrite surfaces below the water line were corroded to a depth of 10-30 µm in both the CO2 and the baseline N2 experiments. This porosity was easily distinguishable from the vuggy porosity developed during diagenesis. Scanning electron microscopy also revealed that a fine coating of halite developed above the water-CO2 interface during the experiment. In the experiments containing crushed Midale Vuggy, euhedral tabular prismatic gypsum crystals up to 1.8 mm long developed after 2 weeks reaction. Only limited evidence for minor corrosion was tentatively observed. After 26 weeks of reaction, the only evidence for dissolution in the <250 µm crushed samples was slightly less ‘dust’ in the baseline N2 experiment relative to the CO2 experiment. It was noted that the CO2 experiments give lower S concentrations compared to the N2 experiments, with S (as SO4) removed from solution by gypsum precipitation. During the early parts of the experiments at least, this appears to be faster than the rate of SO4 addition from anhydrite dissolution. Later in the CO2 experiments steady-state concentrations appear to be reached, and it is likely that saturation with respect to gypsum balances lower S concentrations with higher Ca concentrations. The changes described above were interpreted as being due to some calcite dissolution (probably more than observed in the Midale Marly experiments), some anhydrite dissolution, a little aluminosilicate mineral dissolution and a fair amount of gypsum precipitation. It is still unclear if there is an overall net increase or decrease in porosity or permeability. However, if significant gypsum precipitation reduced the permeability of the Midale Vuggy unit, then this may be a beneficial reaction in terms of the EOR operation, as it might reduce the potential for the injected CO2 to ‘under-ride’ the target Marly unit