Many acidizing treatments in carbonate reservoirs do notproduce expected increase of productivity, especially in the caseof open-hole horizontal wells. This is due to the poor modellingof near well-bore mechanisms. This paper describes a new 2Dnumerical simulator which features a better description of thephysics and which is validated on experimental data.The numerical simulator presents the coupled mechanismsof flow and dissolution at the origin of the wormhole instability.The macroscopic dissolution equation is derived from a volumeaveraging of the advection/diffusion and reaction equationswritten at the pore scale. The flow description is based onDarcy-Brinkman equation which accounts for Darcy’s flow inthe matrix and Stokes flow in the wormhole.Two series of experimental results are used for thevalidation: acidizing experiments with carbonate corespreviously published by IFP and other investigators and newmodel experiments. These experiments consist in injectingunder-saturated salt water into a porous medium made of salt.The dissolution instability, channel development and wormholepropagation are recorded by a video camera.The results predicted by the numerical model reproducemost of the observations in salt and carbonate: 1) the effect ofthe flow rate on the dissolution regime, I.e. compact,wormholing or uniform behaviour; 2) transitions fromwormholing to ramified which slow down the wormholepropagation rate; 3) the effect of the injection conditions on thewormhole propagation rate, the optimum flow rate and themaximum distance of wormhole penetration. Optimumconditions for wormhole propagation are deduced.The model is built to provide relations on wormholepropagation rate depending on the reservoir properties and theinjection conditions. These relations will then be integrated in anear well-bore simulator coupled to a reservoir simulator for abetter design of the acidizing treatments in carbonates.
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