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International audienceThis study focuses on 2D Computational Fluid Dynamics (CFD) numerical modelling of the erosion of a cohesive soil by a circular impinging turbulent jet. Initially, the model is validated in the case of a non erodible flat plate. Several turbulence models are compared to experimental results and to simplified formulas available in the literature. The results obtained show that the Reynolds Stress Model (RSM) is in good agreement with the semi-empirical results in the literature. Nonetheless, the RSM cannot be used with successive remeshings, due to its convergence issues. The shear stress at the wall is well-described by the k-ε model while the pressure is better-described by the k-ω model. The numerical model of erosion is based on adaptive remeshing of the water/soil interface to ensure the good precision of the mechanical values at the wall. The two erosion parameters are the critical shear stress and the erosion coefficient. The results obtained are compared with the semi-empirical model interpreting the Jet Erosion Test. The k-ε model underestimates the shear stress and does not allow simulation of the entire erosion process, whereas the results obtained with the k-ω model agree well with the semi-empirical model and experimental data. A study of the influence of erosion parameters on erosion kinetics and scouring depth shows that the shape and depth of scouring are influenced solely by the critical shear stress while the duration of scouring depends on both erosion parameters. Further research is nonetheless required to better understand the erosion mechanisms in the stagnation zone

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TX 75083-3836, U.S.A., fax 01-972-952-9435. Abstract.Compaction Drive consists in the expulsion of oil due to the reduction of pore volume. Generally, unconsolidated sands display an elasto-plastic behaviour during depletion. The limit between the elastic and the plastic behaviour is called the preconsolidation stress and referred to as P c0 . As long as the effective stress is less than P c0 , the rock behaves elastically and the pore compressibility is low. If ever the effective stress exceeds P c0 , the compressibility increases significantly. In heavy oil fields of unconsolidated sand, the additional recovery due to compaction drive may be estimated between 0.5 and 1 % if the rock remains elastic during the field life and to more than 3% if the plasticity threshold is reached early. Experience has shown that it is almost impossible to determine P c0 from laboratory tests on sand samples, mainly because of cores disturbance. TOTAL has been investigating other methods to determine this parameter. The method presented in this paper is based on : • Laboratory tests on preserved intra-reservoir shales • A shale compaction model derived from the critical state theory of Cam-Clay and calibrated on a normal compaction trend for shales • Geological description of the deposition-erosion history on a basin scale.

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