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Allowing sand to be produced is widely known to enhance oil production rates particularly for heavy-oils fields. However, in such a situation, it is very important to be able to determine the expected sand rate as well as the amount of sand produced during the life of the well. To address this problem, an oedometric cell specially designed to simulate a radial flow towards a well has been developed at IFP. Tests performed under CT-scan on cohesionless sand samples allow to monitor in real time the initiation of the sand production and to follow the development of the sand producing zone. In parallel, a numerical approach is proposed to simulate the dominant sanding mechanism. The theoretical model is based on the resolution of the equations of equilibrium at the interface between the intact zone and the slurry made of eroded sand and oil. An algorithm in 2-D was developed and implemented in a finite element code. Two calculations are alternatively performed: one on the intact zone (rock mass) and one on the slurry, respectively considered as a poroelastic medium and a Newtonian fluid. For each time step, it implies an iterative process to determine the unknown fluid pressure and solid displacements at the interface. The boundary between the slurry and the porous medium evolves as sand is produced. The problem to solve has then a geometry varying with time, but no a priori assumptions are made on the shape of the altered zone. Modeling of the laboratory sand production experiments allows the ability of this model to reproduce the observed sand production mechanisms to be assessed. The influence on the results of numerical (temporal and geometrical discretization) parameters is also discussed. |
