Generally, in classical reservoir studies, the geomechanical behavior of the porous medium is taken into account by the rock compressibility. Inside the reservoir simulator, the rock compressibility is assumed to be constant or to vary with the pressure of the oil phase. It induces some changes in the porosity field.During the depletion phase or the cold-water injection of highpressure/high-temperature (HP/HT) reservoirs, the stress state in and around a reservoir can change dramatically. This process might result in rock movements such as compaction, induced fracturing, and enhancement of natural fractures and/or fault activation, which continuously modify the reservoir properties such as the permeabilities and the fault transmissibilities.Modifications of such parameters strongly affect the flow pattern in the reservoir and ultimately the recovery factor.To capture the link between flow and in-situ stresses, it becomes essential to conduct coupled reservoir-geomechanical simulations.This paper compares the use of five types of approach for the reservoir simulations:• A classical approach with rock compressibility using only a reservoir simulator.• A loose coupled approach between a reservoir simulator (finite volumes) and a geomechanical simulator (finite elements). At given user-defined steps, the hydrocarbon pressures calculated by the reservoir simulator are transmitted to the geomechanical tool, which computes the actual stresses and feeds back iteratively the modifications of the petrophysical properties (porosities and permeabilities) to the reservoir simulator.• A one-way coupling: this approach is a simplification of the loose coupled approach in that the modifications are not fed back to the reservoir simulator.• A simplified approach using permeability and porosity multipliers inside a reservoir simulator. These multipliers are userdefined curves and vary with the pressure of the oil phase. This approach uses only a reservoir simulator.• A coupled approach in which the structural and the flow unknowns (displacement, pressure, and saturations) are solved simultaneously.These approaches are compared for two validation cases and two field cases described in the following.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractGenerally, in classical reservoir studies, the geomechanical behavior of the porous media is taken into account by the rock compressibility. Inside the reservoir simulator, the rock compressibility is assumed to be constant or to vary with the pressure of the oil phase. It induces some changes in the porosity field. During the depletion phase or the cold water injection of HP-HT reservoirs, the stress state in and around a reservoir can change dramatically. This process might result in rock movements such as compaction, induced fracturing, enhancement of natural fractures and/or fault activation, which continuously modify the reservoir properties such as the permeabilities and the fault transmissibilities. Modifications of such parameters strongly affects the flow pattern in the reservoir and ultimately the recovery factor. To capture the link between flow and in situ stresses, it becomes essential to conduct coupled reservoirgeomechanical simulations. This paper compares the use of 5 types of approach for the reservoir simulations:A classical approach with rock compressibility using only a reservoir simulator, A loose coupled approach between a reservoir simulator (finite volumes) and a geomechanical simulator (finite elements). At given user-defined steps, the hydrocarbons pressures calculated by the reservoir simulator are transmitted to the geomechanical tool which computes the actual stresses and feeds back the modifications of the petrophysical properties (porosities and permeabilities) to the reservoir simulator. A one way coupling: this approach is a simplification of the loose coupled approach, the modifications are not fed back to the reservoir simulator.A simplified approach using permeability and porosity multipliers inside a reservoir simulator. These multipliers are user defined curves and vary with the pressure of the oil phase. This approach uses only a reservoir simulator. A fully coupled approach where the structural and the flow unknows (displacement, pressure, saturations) are solved simultaneously. These approaches are compared for 2 field cases described below.

The precise control of geometric models plays an important role in many domains such as Computer Aided geometric Design and numerical simulation. For shape optimisation in Computational Fluid Dynamics, the choice of control parameters and the way to deform a shape are critical. In this paper, we describe a skeleton-based representation of shapes adapted for CFD simulation and automatic shape optimisation. Instead of using the control points of a classical B-spline representation, we control the geometry in terms of architectural parameters. We assure valid shapes with a strong shape consistency control. Deformations of the geometry are performed by solving optimisation problems on the skeleton. Finally, a surface reconstruction method is proposed to evaluate the shape's performances with CFD solvers. We illustrate the approach on two problems: the foil of an AC45 racing sail boat and the bulbous bow of a fishing trawler. For each case, we obtained a set of shape deformations and then we evaluated and analysed the performances of the different shapes with CFD computations.

International audienceIn this work, we improve an existing pseudospectral algorithm, in order to extend its properties to a multidomain patching of a rotating cavity. Viscous rotating flows have been widely studied over the last decades, either on industrial or aca-demic approaches. Nevertheless, the range of Reynolds numbers reached in indus-trial devices implies very high resolutions of the spatial problem, which are clearly unreachable using a monodomain approach. Hence, we worked on the multido-main extension of the existing divergence-free Navier-Stokes solver with a Schur approach. The particularity of such an approach is that it does not require any sub-domain superposition: the value of a variable on the boundary between two adjacent subdomains is treated as a boundary condition of a local Helmholtz solver. This value is computed on a direct way via a so-called continuity influence matrix and the derivative jump of an homogeneous solution computed independently on each subdomain. Such a method is known to have both good scalability and accuracy. It has been validated on two well documented three-dimensional rotating flows

The precise control of geometric models plays an important role in many domains such as computer-aided geometric design and numerical simulation. For shape optimization in computational fluid dynamics (CFD), the choice of control parameters and the way to deform a shape are critical. In this article, we describe a skeleton-based representation of shapes adapted for CFD simulation and automatic shape optimization. Instead of using the control points of a classic B-spline representation, we control the geometry in terms of architectural parameters. We assure valid shapes with a strong shape consistency control. Deformations of the geometry are performed by solving optimization problems on the skeleton. Finally, a surface reconstruction method is proposed to evaluate the shape's performances with CFD solvers. We illustrate the approach on two problems: the foil of an AC45 racing sail boat and the bulbous bow of a fishing trawler. For each case, we obtained a set of shape deformations and then we evaluated and analyzed the performances of the different shapes with CFD computations.