A large scale dual-porosity approach for the ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

A large scale dual-porosity approach for the modeling of the wormholing phenomenon
Author:Michel QUINTARD <michel.quintard@imft.fr> (Institut de Mécanique des Fluides de Toulouse)
Brigitte BAZIN <brigitte.bazin@ifp.fr> (Institut Français du Pétrole)
Charles Edouard COHEN <charles.cohen@ifp.fr> (Institut Français du Pétrole)
Didier DING <d-yu.ding@ifp.fr> (Institut Français du Pétrole)
Presenter:Charles Edouard COHEN <charles.cohen@ifp.fr> (Institut Français du Pétrole)
Date: 2006-06-18     Track: Special Sessions     Session: Multi-Disciplinary Approaches To Reactive Transport Simulation In Aquifer Systems

Acid treatment is frequently used in the oil industry to improve well productivity. It is achieved in carbonate reservoir by taking advantage of a macroscopic instability which creates empty channels (wormholes) bypassing the damaged areas and improving near wellbore permeability. Length, size and density of these channels depend on numerous parameters from injection rate to rock properties. Resulting dissolution patterns have been extensively studied and several models proposed. Today, core-scale numerical models can successfully reproduce the dissolution physical mechanism, but they are limited in their ability to predict skin effect at the wellbore scale. As a consequence, large-scale models are based on semi-empirical approaches. Productivity improvement resulting from acidizing treatments cannot be predicted unless radial flow and heterogeneities are considered. In this paper, we present a large scale model obtained through upscaling techniques from the core-scale model. The dual-porosity concept is introduced in this model to take into account the different physical processes occurring in the wormholes and matrix areas. Acid transport equation and rock dissolution equations are written for each media. A transfer term is introduced to describe fluid exchange between these two media. Examples show that the dual-porosity model can be used to describe carbonate acidizing at large scale. This model can reproduce different types of dissolution pattern, from compact to uniform. To determine physical parameters in the dual-porosity model, an inversion procedure based on a Levenberg-Marquart algorithm is developed to match experimental data or data from core-scale model simulations. An objective function is built to optimize pressure drop, porosity, and other parameters, at different time and space steps. This approach is illustrated by several examples. The developed large-scale dual-porosity model will be used for 3D near-wellbore simulation to evaluate skin along acidified well sections. In this way, we will be able to design an optimum acid stimulation procedure for field applications.