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The dynamic evolution with frictional contact of an elastic body is considered. In modeling the contact the Tresca model and a slip-dependent friction law are used. The existence of a solution is proved in the two-dimensional case. The uniqueness is proved for the one-dimensional shearing problem. The convergence, for a vanishing viscosity, of the unique solution of the viscoelastic problem to a solution of the elastic problem is obtained. [Copyright &y& Elsevier]

Abstract: Shale reservoirs have not benefited from advanced modeling tools to the extent of conventional resources. Thus an approach is proposed to integrate key parameters, such as total organic carbon (TOC) content, methane adsorption and organic porosity in a basin simulator. Original TOC has an impact on both gas generated volume and gas retention within source rocks. The conversion of organic matter into hydrocarbons also creates additional intraparticle kerogen porosity in which oil and gas can be stored. In this work, a method is proposed to calculate the evolution of TOC, organic porosity and gas retention capacity (free versus adsorbed) through time in shale gas by means of petroleum system modeling. Gas adsorption potential on organic material is calculated using a Langmuir model, which accounts for pressure, temperature and remaining solid TOC. Organic porosity is calculated as the result of the change of the organic matter from solid immature kerogen to less dense fluid hydrocarbons during thermal maturation. The method is tested on a 3D basin model of the Mississippian Barnett Shale in Texas (USA). The computed organic porosity varies from 0% in immature zones, to a maximum of 4% of rock volume in organic-rich and mature zones. Computed retained methane in the Lower Barnett Shale ranges between 20 and 60 scf/t (from 1 to nearly 3 kg/m3) and is mainly concentrated in mature areas of the basin. Simulated results are consistent with available Barnett Shale data. Possible effects of assumptions made in the approach and perspectives are discussed. [Copyright &y& Elsevier]

Marine sediments near continental margins contain sedimentary organic matter (SOM) which is subject to the metabolic activity of micro-organisms during early diagenesis resulting in production of biogenic methane. This process occurs at microscopic scale and anaerobic conditions. Here, we apply a new numerical approach to simulate biogenic methane production offshore Aquitaine (Bay of Biscay) where gas seeps have been recently observed as the result of microbial activity. This new approach accounts for: (1) degradation of a labile-SOM fraction to methane, (2) first order kinetics of the thermal degradation of a thermo-labile-SOM fraction into labile fraction at greater burial and (3) decrease of SOM reactivity with time. First, the organic matter is characterized through pyrolysis using Rock-Eval performed on cuttings collected from two wells located within the methane seepage area. The microbial system is fed from a type III continental-derived SOM which is immature (average Tmax < 425 °C). The basin model is built and calibrated on seismic and well data. It accounts for the consumption of methane required to precipitate methane-derived authigenic carbonates which are found widely distributed on the seafloor as the result of the anaerobic oxidation of methane during upward migration. A sensitivity analysis is performed on the main model input parameters to quantify their impact on the biogenic gas production and expulsion/migration processes. Results led to a reference scenario for microbial gas production in offshore Aquitaine. With this model the generated methane is predominantly dissolved in water and transported by advective processes. Migration is mainly vertical from the source rock layers to the seafloor and controlled by sediment porosity and strata geometry. Modelling can reproduce natural processes such as gas migration at emission points (gas seeps) which have been previously mapped in the offshore Aquitaine Basin. Our results suggest that the biogenic methane is sourced by a present-day active system with a mean flow rate of 27 Mg/y which is relatively lower than flux modelled during the early Pleistocene reaching up to 41 Mg/y. Calculated total methane lost to the seafloor along the Aquitaine Shelf is in accordance with methane flow rate estimated from in situ measurements and acoustic signatures of bubbling sites, and ranges between 0.87 Tcf/My and 1.48 Tcf/My. Here we propose a new workflow to assess and predict biogenic gas occurrences in offshore environment at the basin scale where gas is sourced by recent continental-derived organic matter. This new approach can help to better assess the total biogenic methane budget emitted naturally in the shelf area of oceans that may reach the atmosphere with a negative impact on climate and environment. • Innovative 3D basin modelling approach to quantify the budget of biogenic methane in continental shelf areas. • Sensitivity analysis to determine impact of main parameters on biogenic gas processes in offshore Aquitaine. • Quantification of methane consumed as function of efficiency of AOM (Anaerobic Oxidation of Methane). • Methane migration is diffuse and mainly vertical from the source rock layers to the seafloor dissolved in pore water. • Biogenic methane is sourced by an active system with a maximum flow rate modelled during the early Pleistocene. [ABSTRACT FROM AUTHOR]

Professional cooperation protocols have recently been developed by the French national health authority and regional health agencies. They enable paramedical staff to perform procedures usually carried out by doctors. In the framework of bariatric surgery, the follow-up of patients after surgery is thereby assured by specialist nurses. They can make a diagnosis and prescribe vitamins, minerals and tests., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)