Numerical modeling of regional stress distributions for geothermal exploration

International audienceAny high-enthalpy unconventional geothermal projectcan be jeopardized by the uncertainty on the presence of the geothermal resource at depth. Indeed, for the majority of such projects the geothermal resource is deeply seated and, with the drilling costs increasing accordingly, must be located as precisely as possible to increase the chance of their economic viability. In order to reduce the " geological risk " , i.e. the chance to poorly locate the geothermal resource, a maximum amount of information must be gathered prior to any drilling of exploration and/or operational well. Cross-interpretation from multiple disciplines (e.g., geophysics, hydrology, geomechanics. . .) should improve locating the geothermal resource and so the position of exploration wells ; this is the objective of the Euro-pean project IMAGE (grant agreement No. 608553), under which the work presented here was carried out. As far as geomechanics is concerned, in situ stresses can have a great impact on the presence of a geothermal resource since they condition both the regime within the rock mass, and the state of the major fault zones (and hence, the possible flow paths). In this work, we propose a geomechanical model to assess the stress distribution at the regional scale (characteristic length of 100 kilometers). Since they have a substantial impact on the stress distributions and on the possible creation of regional flow paths, the major fault zones are explicitly taken into account. The Distinct Element Method is used, where the medium is modeled as fully deformable blocks representing the rock mass interacting through mechanically active joints depicting the fault zones. The first step of the study is to build the model geometry based on geological and geophysical evidences. Geophysical and structural geology results help positioning the major fault zones in the first place. Then, outcrop observations, structural models and site-specific geological knowledge give information on the fault zones family sets and their priority rule. In the second step, the physical model must be established, including constitutive equations for the rock mass and the fault zones, initial state and boundary conditions. At such large scales, physical laws and parameters are difficult to assess and must be constrained by sensitivity analysis. In the last step of the study, the results can be interpreted to highlight areas where the mechanical conditions favor the presence of a geothermal resource. The DEM enables accounting for the strong stress redistributions inherent to highly-segmented geometries, and to the dilational opening of fault zones under shearing. A 130x150 square-kilometers region within the Upper Rhine Graben is used as a case-study to illustrate the building and interpretation of a regional stress model

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Advanced rotorcraft aeromechanics studies in the French-German SHANEL project

The present paper gives an overview of the SHANEL research project (partly supported by the French DGAC and the German BMWA) which was started at the end of 2006 between the German and French Aerospace Research Centres DLR and ONERA, the University of Stuttgart and the two national helicopter manufacturers, Eurocopter and Eurocopter Germany. This program represents the continuation of the binational CHANCE project, involving the same partners. The objective of the project is to enhance and further validate the CFD tools: the structured multi-block elsA software of Onera and the unstructured TAU code of DLR, for computing the aerodynamics of the complete trimmed helicopter, accounting for the blade elasticity by coupling with blade dynamics and structural mechanics tools. A coupling activity between the FLOWer code of DLR and the HOST tool of Eurocopter is also completed to achieve the free flight trim of a complete helicopter. In this program particular attention is being given to wake conservation, to the modelling of elaborated complex shapes such as rotor hubs and consequently to interactional phenomena, with the global objective of improving the prediction of helicopter performance and noise. Rotorcraft noise prediction chains were rationalized, enhanced and compared. The validation activity of the flow solvers elsA and TAU is progressing from the CHANCE results and is now focussing on more complex problems such as the simulation of a rotating rotor head mounted on its fuselage, of a complete helicopter in steady mode through the use of actuator discs and engine boundary conditions, the time-accurate simulation of a complete trimmed helicopter in forward-flight, and the numerical simulation of Blade Vortex Interactions. All along the research program the updated versions of the CFD and acoustic codes are systematically delivered to industry. This approach, also followed during the former CHANCE project, is chosen to speed up the transfer of capabilities to industry and check early enough that the products meet the expectations for applicability in the industrial environment of Eurocopter

Study of Thermo-Mechanical Damage around Deep Geothermal Wells: from the Micro-Processes to Macroscopic Effects in the Near Well

International audienceThe different processes involved in the life of a geothermal well, from drilling to exploitation, can damage the rock mass in the near well area. In this paper, we propose to study the potential damage linked to the mechanical and thermo-mechanical effects of the well drilling, the well development and the well exploitation. The cooling of the rock mass of the near well pre-damaged by drilling process is a complex phenomenon with the superimposition of different kind of loadings at different scale that lead us to use modeling with a micro-macro approach. To confront the results of the modeling with the reality, we propose to base our study on real cases. For studying mechanical and thermo-mechanical loadings due to drilling and development of the well, we focus our study on the granitic reservoir exploited in the framework of the enhanced geothermal system (EGS) of Soultz-sous-Forêts (France). The study of the thermo-mechanical loading due to well exploitation is performed for a sandstone in the conventional heat exploitation of Melleray (Loiret, France). These simulations highlight the thermo-mechanical damage of a geothermal well linked to the different steps of its life

Modélisations mécanique et hydraulique pour la compréhension des interactions fluide/roche en fracture : Mechanical and hydraulic modelling for the understanding of fluid/rock interactions in fracture

Les modèles hydraulique et mécanique mis en œuvre pour aider à la compréhension et à l'interprétation des essais de percolation réactive en fracture sont présentés. Ces modèles sont basés sur la construction d'un modèle géométrique à partir de données morphologiques de la fracture. Hydraulic and mechanical models implemented to improve the understanding of reactive percolation tests in a fracture are presented. Both models are based on the construction of a geometrical model built on the base of morphological data

Locating Geothermal Resources: Insights from 3D Stress and Flow Models at the Upper Rhine Graben Scale

To be exploited, geothermal resources require heat, fluid, and permeability. These favourable geothermal conditions are strongly linked to the specific geodynamic context and the main physical transport processes, notably stresses and fluid circulations, which impact heat-driving processes. The physical conditions favouring the setup of geothermal resources can be searched for in predictive models, thus giving estimates on the so-called “favourable areas.” Numerical models could allow an integrated evaluation of the physical processes with adapted time and space scales and considering 3D effects. Supported by geological, geophysical, and geochemical exploration methods, they constitute a useful tool to shed light on the dynamic context of the geothermal resource setup and may provide answers to the challenging task of geothermal exploration. The Upper Rhine Graben (URG) is a data-rich geothermal system where deep fluid circulations occurring in the regional fault network are the probable origin of local thermal anomalies. Here, we present a current overview of our team’s efforts to integrate the impacts of the key physics as well as key factors controlling the geothermal anomalies in a fault-controlled geological setting in 3D physically consistent models at the regional scale. The study relies on the building of the first 3D numerical flow (using the discrete-continuum method) and mechanical models (using the distinct element method) at the URG scale. First, the key role of the regional fault network is taken into account using a discrete numerical approach. The geometry building is focused on the conceptualization of the 3D fault zone network based on structural interpretation and generic geological concepts and is consistent with the geological knowledge. This DFN (discrete fracture network) model is declined in two separate models (3D flow and stress) at the URG scale. Then, based on the main characteristics of the geothermal anomalies and the link with the physics considered, criteria are identified that enable the elaboration of indicators to use the results of the simulation and identify geothermally favourable areas. Then, considering the strong link between the stress, fluid flow, and geothermal resources, a cross-analysis of the results is realized to delineate favourable areas for geothermal resources. The results are compared with the existing thermal data at the URG scale and compared with knowledge gained through numerous studies. The good agreement between the delineated favourable areas and the locations of local thermal anomalies (especially the main one close to Soultz-sous-Forêts) demonstrates the key role of the regional fault network as well as stress and fluid flow on the setup of geothermal resources. Moreover, the very encouraging results underline the potential of the first 3D flow and 3D stress models at the URG scale to locate geothermal resources and offer new research opportunities

Efficacy and safety of rituximab in patients with chronic hypersensitivity pneumonitis (cHP): A retrospective, multicentric, observational study

International audienceBackground: There are chronic forms of hypersensitivity pneumonitis (cHP) that can progress to pulmonary fibrosis. There is no recommended treatment for patients whose respiratory condition continues to deteriorate in spite of antigen avoidance. Whether rituximab may be beneficial to patients with cHP is unknown. The aim of this study was to describe the course of 20 patients with cHP under rituximab therapy.Methods: This retrospective study was conducted from November 2018 to July 2019 in 7 French university hospitals. Forced Vital Capacity (FVC) was measured 6 months before rituximab therapy onset (M - 6), at rituximab onset (M0), and 6 months later (M+6).Results: FVC decreased significantly in the 6 months preceding the introduction of rituximab (65% [44; 112%] at M - 6 versus 59% [39; 102%] at M0; p = 0.0001), but it did not differ significantly from that at 6 months after the introduction of rituximab (61% [38; 99%]). The decline in FVC between M0 and M+6 (-3% [-15; +19%]) was significantly less than between M - 6 and M0 (-8% [-21; 0%]) (p = 0.0002). Between M0 (37% [16; 73%]) and M + 6 (45% [15; 70%]), the median DLCO remained stable (p = 0.12). DLCO improved at M+6 in 5 of the 8 patients (63%) for whom a DLCO value was available at M+6 improved their DLCO.Conclusion: Rituximab seems well tolerated, and may lead to stabilization or improvement of lung function in some patients

Rituximab for auto-immune alveolar proteinosis, a real life cohort study

International audienceBackground: Whole lung lavage is the current standard therapy for pulmonary alveolar proteinosis (PAP) that is characterized by the alveolar accumulation of surfactant. Rituximab showed promising results in auto-immune PAP (aPAP) related to anti-GM-CSF antibody.Methods: We aimed to assess efficacy of rituximab in aPAP in real life and all patients with aPAP in France that received rituximab were retrospectively analyzed.Results: Thirteen patients were included. No patients showed improvement 6 months after treatment, but, 4 patients (30%) presented a significant decrease of alveolar-arterial difference in oxygen after 1 year. One patient received lung transplantation and one patient was lost of follow-up within one year. Although a spontaneous improvement cannot be excluded in these 4 patients, improvement was more frequent in patients naive to prior specific therapy and with higher level of anti-GM-CSF antibodies evaluated by ELISA. No serious adverse event was evidenced. Conclusions: These data do not support rituximab as a second line therapy for patients with refractory aPAP

Genes Chromosomes Cancer

Myelodysplastic syndromes (MDS) are hematological malignancies classically defined by the presence of cytopenia(s) and dysmorphic myeloid cells. It is now known that MDS can be preceded by a pre-malignant condition called clonal cytopenia of unknown significance (CCUS), which associates a clonality marker with cytopenia in the absence of criteria of dysplasia. However, to date, it is not clear whether chromosomal abnormalities should be considered in the definition of CCUS or if they carry a prognostic impact in CCUS patients. In this study, we analyzed the clinico-biological features and outcomes of 34 patients who presented with one or more cytopenias, an absence of significant dysplasia, and a presence of a chromosomal abnormality (CA). We named this entity chromosomal abnormality with cytopenia of undetermined significance (CACtUS). We show that these patients are slightly older than MDS patients and that they more frequently presented with normocytic anemia. Most CACtUS patients exhibited only one unbalanced CA. The number and type of mutations were comparable between CACtUS patients and MDS patients. Regardless of the cytogenetic abnormality, the clinicobiological characteristics, overall survival, and risk of progression to high-risk (HR) MDS were similar between CACtUS patients and low-risk MDS patients. Thus, we suggest that CACtUS patients can be considered as HR-CCUS and should receive the follow-up regimen recommended for MDS patients