Modeling, Simulation and Comparison of Models for Wormhole Formation duringMatrix Stimulation of Carbonates

摘要

A new averaged/continuum model is presented forrnsimulation of wormhole formation during matrix stimulationrnof carbonates. The model presented here differs from existingrnliterature models in three fundamental aspects. First, we showrnthat the dissolution process creates a Darcy velocity field withrnnon-zero divergence. Second, we use two concentrationrnvariables to account for the local gradients at the pore levelrncaused by the coupling between the flow, species diffusionrnand chemical reaction. Third, we account for both thernasymptotic/diffusive and convective contributions to the localrnmass transfer coefficient between the fluid and solid. Wernargue that models that do not account for these effects do notrnretain the qualitative features of the reactive dissolutionrnprocess and hence cannot be predictive. The averaged modelrndeveloped here accounts for pore level physics by coupling thernlocal pore scale phenomena to the macroscopic variablesrn(Darcy velocity, pressure and reactant cup-mixingrnconcentration) through the structure-property relationshipsrn(permeability-porosity, average pore size-porosity andrninterfacial area-porosity), and the dependence of the fluidsolidrnmass transfer coefficient and fluid phase dispersionrncoefficient on the evolving pore scale variables (average porernsize and local Reynolds and Schmidt numbers).rnA preliminary analysis of the model is presented and therninfluence of various factors on flow channeling is examinedrnusing the new model. The model predictions are comparedrnwith the available laboratory data.