Sink or float: microtextural controls on the fate of pumice deposition during the 2012 submarine Havre eruption

Silicic submarine volcanic eruptions can produce large volumes of pumices that may rise buoyantly to the ocean surface and/or sink to the seafloor. For eruptions that release significant volumes of pumice into rafts, the proximal to medial submarine geologic record is thus depleted in large volumes of pumice that would have sedimented closer to source in any subaerial eruption. The 2012 eruption of Havre volcano, a submarine volcano in the Kermadec Arc, presents a unique opportunity to study the partitioning of well-constrained rafted and seafloor pumice. Macro- and microtextural analysis was performed on clasts from the Havre pumice raft and from coeval pumiceous seafloor units around the Havre caldera. The raft and seafloor clasts have indistinguishable macrotextures, componentry, and vesicularity ranges. Microtextural differences are apparent as raft pumices have higher vesicle number densities (109 cm−3 vs. 108 cm−3) and significantly lower pore space connectivity (0.3–0.95 vs. 0.9–1.0) than seafloor pumices. Porosity analysis shows that high vesicularity raft pumices required trapping of gas in the connected porosity to remain afloat, whereas lower vesicularity raft pumices could float just from gas within isolated porosity. Measurements of minimum vesicle throat openings further show that raft pumices have a larger proportion of small vesicle throats than seafloor pumices. Narrow throats increase gas trapping as a result of higher capillary pressures acting over gas–water interfaces between vesicles and lower capillary number inhibiting gas bubble escape. Differences in isolated porosity and pore throat distribution ultimately control whether pumices sink or float and thus whether pumice deposits are preserved or not on the seafloor.

Analysis of Reservoir Fluid Migration in the Process of CO2 Sequestration in a Partially Depleted Gas Reservoir

This paper addresses problems of reservoir fluid migrations in the process of CO2 sequestration in a partially depleted petroleum reservoir. A detailed analysis of the migrations is required to obtain fundamental characteristics of a sequestration structure, including estimation of its sequestration capacity and leakage risks. The paper presents a general discussion of the relevant mechanisms and their contributions to the analysed issues. The proposed approach to solve the problems relies on the usage of numerical structure modelling and simulations of the sequestration processes on numerical models of the structure. It is applied to a selected geological structure comprising a partially depleted gas reservoir. The modelling includes key types of reservoir fluid migrations: viscous multiphase transport and convection transport. It also takes into account other phenomena that affect fluid migrations including injected gas solubility in the formation water and gas trapping by capillary forces. Correspondingly, the leakage risks are associated with distinct leakage pathways (beyond the structural trap, to the caprock, via activated fractures). All these cases are separately modelled and their detailed characteristics are presented and discussed. The final results of the fluid migrations and their consequences for the leakage events are discussed and some generalized conclusions are drawn from the approach employed in the study.

Nasal High Flow at 25 L/min or Expiratory Resistive Load Do Not Improve Regional Lung Function in Patients With COPD: A Functional CT Imaging Study

BackgroundNasal high flow (NHF) is a non-invasive breathing therapy that is based on the delivery via a large-caliber nasal cannula of heated and humidified air at flow rates that exceed peak inspiratory flow. It is thought that positive airway pressure generated by NHF can help reduce gas trapping and improve regional lung ventilation. There are no data to confirm this hypothesis at flow rates applicable in stable chronic obstructive pulmonary disease (COPD) patients.MethodsIn this study, we used non-rigid registration of computed tomography (CT) images acquired at maximal expiration and inspiration to compute regional lung attenuation changes (ΔHU), and lung displacement (LD), indices of regional lung ventilation. Parametric response maps (Galban et al., 2012) were also computed in each experimental condition. Eight COPD patients were assessed at baseline (BL) and after 5 min of NHF and expiratory resistive loading (ERL).ResultsΔHU was: BL (median, IQR): 85 (67.2, 102.8); NHF: 90.7 (57.4, 97.6); ERL: 74.6 (46.4, 89.6) HU (p = 0.531); and LD: 27.8 (22.3, 39.3); 17.6 (15.4, 27.9); and 20.4 (16.6, 23.6) mm (p = 0.120) in the 3 conditions, respectively. No significant difference in trapping was observed. Respiratory rate significantly decreased with both treatments [BL: 17.3 (16.4, 18.9); NHF: 13.7; ERL: 11.4 (9.6, 13.2) bpm; and p < 0.001].ConclusionNeither NHF at 25 L/min nor ERL significantly improved the regional lung ventilation of stable COPD patients with gas trapping, based on functional lung CT imaging. Further study including more subjects is needed to assess the potential effect of NHF on regional lung function at higher flow rates.Clinical Trial Registrationwww.clinicaltrials.gov/under, identifier NCT03821311.

Effects of Gas Trapping on Foam Mobility in a Model Fracture

In enhanced oil recovery, foam can effectively mitigate conformance problems and maintain a stable displacement front, by trapping gas and reducing its relative permeability in situ. In this study, to understand gas trapping in fractures and how it affects foam behavior, we report foam experiments in a 1-m-long glass model fracture with a hydraulic aperture of 80 $$\upmu $$ μ m. One wall of the fracture is rough, and the other is smooth. Between the two is a 2D porous medium representing the aperture in a fracture. The fracture model allows direct visualization of foam inside the fracture using a high-speed camera. This study is part of a continuing program to determine how foam behaves as a function of the geometry of the fracture pore space (AlQuaimi and Rossen in Energy & Fuels 33: 68-80, 2018a). We find that local equilibrium of foam (where the rate of bubble generation equals that of bubble destruction) has been achieved within the 1-m model fracture. Foam texture becomes finer, and less gas is trapped as interstitial velocity, and pressure gradient increase. Shear-thinning rheology of foam has also been observed. The fraction of trapped gas is significantly lower in our model (less than 7%) than in 3D geological pore networks. At the extreme, when velocity increases to 7 mm/s, there is no gas trapped inside the fracture. Our experimental results of trapped-gas fraction correlate well with the correlation of AlQuaimi and Rossen (SPE J 23: 788-802, 2018b) for fracture-like porous media. This suggests that the correlation can also be applied to gas trapping in fractures with other geometries. Article Highlights We have made a lab-scale 1-meter-long transparent glass model representing a geological fracture with roughened surface, and we have implemented a direct method of image analysis to quantify the texture of bubbles in the fracture and to link the texture with the strength of the foam; We have successfully created surfactant-stabilized foam flow inside the fracture and examined its stability along the 1-meter-long fracture; We explain the mechanism of gas trapping in fractures and how it affects foam behavior. We also discuss how viscous force and capillary force affect gas trapping in fractures at our experimental conditions. Graphic Abstract

COVID-19: Risikofaktor Adipositas – seine Relevanz und die ursächlichen pathophysiologischen Mechanismen

ZusammenfassungDie Frage nach einer Assoziation von Risikofaktoren mit der „Coronavirus Disease 2019“ (COVID-19), die durch die Infektion mit dem Virus SARS-CoV-2 ausgelöst wird, kann aktuell nicht relevanter sein.In der ersten deutschen Analyse der Uniklinik Aachen, aber auch in weiteren internationalen Studien konnte eine erhöhte Prävalenz an Übergewicht bzw. Adipositas unter den Erkrankten gezeigt werden. Eine Korrelation der Höhe des BMI mit der Schwere der Erkrankung und der Dauer und Notwendigkeit der Therapie wird deutlich. Zudem sorgt das Vorliegen einer Adipositas für das Erkranken von Patienten mit jüngerem Lebensalter.Pathophysiologisch bieten zahlreiche Mechanismen eine mögliche Begründung. Hierunter zählen die Veränderung und Einschränkung der Organfunktion durch Akkumulation von Fettgewebe, aber auch die erhöhte Expression von ACE-2-Rezeptoren, die als Bindeprotein des SARS-CoV-2 das Eindringen in die Zelle ermöglichen. Durch die Freisetzung von Adipokinen kommt es zu einer chronischen pro-inflammatorischen Situation mit veränderter immunozellulären Abwehr und über eine veränderte Insulinreaktion zu einer höheren Prävalenz eines Diabetes mellitus mit daraus folgender schlechterer Krankheitsprognose. Dies erzeugt einen negativen Effekt auf die Lungenfunktion. Es kommt dort durch die Fettablagerung zu einer reduzierten systemischen Compliance und zu einer erhöhten Sensibilität für respiratorische Infektionen. Zudem zeigen sich im Rahmen einer Adipositas ein erniedrigtes exspiratorisches Reservevolumen, „gas trapping“ und eine resultierende systemische Hypoxie.Der spezifische Tropismus unterschiedlicher Viren hin zu Adipozyten unterstreicht durch den Aspekt der Viruspersistenz und chronischen Immunaktivität zusätzlich zu den anderen genannten Punkten die Bedeutung des Risikofaktors Adipositas im Zusammenhang mit dem Progress und der Therapie von COVID-19, aber auch anderer viraler Erkrankungen.

The TRIFLOW study: a randomised, cross-over study evaluating the effects of extrafine beclometasone/formoterol/glycopyrronium on gas trapping in COPD

Background The effects of triple therapy on gas trapping in COPD are not fully understood. We evaluated the effects of the long acting bronchodilator components of the extrafine single inhaler triple therapy beclometasone dipropionate/formoterol/glycopyrronium (BDP/F/G) pMDI on gas trapping. Methods This open-label, randomised, single centre, 2-way cross-over study recruited 23 COPD patients taking inhaled corticosteroid combination treatments and with residual volume (RV) > 120% predicted at screening. Inhaled BDP was taken during run-in and washout periods. Baseline lung function (spirometry, lung volumes, oscillometry) was measured over 12 h prior to randomisation to BDP/F/G or BDP/F for 5 days followed by washout and crossover. Lung function was measured prior to dosing on day 1 and for 12 h post-dose on day 5. Results Co-primary endpoint analysis: BDP/F/G had a greater effect than BDP/F on FEV1 area under the curve over 12 h (AUC0–12) (mean difference 104 mls, p = 0.0071) and RV AUC0–12 (mean difference − 163 mls, p = 0.0028). Oscillometry measurements showed a greater effect of BDP/F/G on the difference between resistance at 5 and 20 Hz (R5–R20) AUC0–12, which measures small airway resistance (mean difference − 0.045 kPa/L/s, p = 0.0002). Comparison of BDP/F with the baseline measurements (BDP alone) showed that F increased FEV1 AUC0–12 (mean difference 227 mls) and improved RV AUC0–12 (mean difference − 558 mls) and R5–R20 AUC0–12 (mean difference − 0.117 kPa/L/s), all p < 0.0001. Conclusions In COPD patients with hyperinflation, the G and F components of extrafine BDP/F/G improved FEV1, RV and small airway function. These long acting bronchodilators target small airway function, thereby improving gas trapping and airflow. Trial registration The study was retrospectively registered at ClinicalTrials.gov on 15th February 2019 (No.: NCT03842904, https://clinicaltrials.gov/ct2/show/NCT03842904).

Nasal High Flow at 25 L/min or Expiratory Resistive Load do Not Improve Regional Lung Function in Patients with COPD: A Functional CT Imaging Study

Background: Nasal high flow (NHF) is a non-invasive breathing therapy that is based on the delivery via a large-caliber nasal cannula of heated and humidified air at flow rates that exceed peak inspiratory flow. It is thought that positive airway pressure generated by NHF can help reduce gas trapping and improve regional lung ventilation. There are no data to confirm this hypothesis at flow rates applicable in stable COPD patients.Methods: In this study, we used non-rigid registration of CT images acquired at maximal expiration and inspiration to compute regional lung attenuation changes (ΔHU), and lung displacement (LD), indices of regional lung ventilation. Eight COPD patients were assessed at baseline (BL) and after 5 min of NHF and expiratory resistive loading (ERL).Results: ΔHU was: BL: 81.7±28.8; NHF: 77.3±28.1; ERL: 70±26.7 HU (p=0.164) and LD: 30.2±12.7; 21.9±10.1 and 20.6±5.8 mm (p=0.044) in the 3 conditions, respectively. Respiratory rate significantly decreased with both treatments (BL:17.6±2.9; NHF:13±3.6; ERL: 11.6±2.8 bpm; p<0.001) while end-expiratory volume tended to increase.Conclusions: Neither NHF at 25 L/min nor ERL significantly improve the regional lung ventilation of stable COPD patients with gas trapping, based on the registration of expiratory and inspiratory CT images. Further studies are needed to assess the potential effect of higher flow rates of NHF.Trial registration: This study was registered with https://clinicaltrials.gov/ under: NCT03821311.