Abstract

A phenomenological model for formation damage in petroleum reservoirs is presented to describe the rock/fluid petroleum reservoirs is presented to describe the rock/fluid interaction processes including particle migration, physico-chemical interactions between invading fluid and reservoir rock, and geochemical reactions. Chemical reactions involving dissolution/precipitation and ion exchange are modeled. The precipitates are considered movable and mixed with other fine precipitates are considered movable and mixed with other fine particles to contribute to the pore throat plugging. Size particles to contribute to the pore throat plugging. Size distribution of both precipitates and clay fines are accounted for by a bimodal distribution function. A probabilistic approach is used to calculate the fraction of the plugged pore throats. The model parameters are determined through an optimization method by fitting with experimental data.

The capability and validity of the model are demonstrated by comparing the predictions obtained from this model with previously published experimental data. The specific case considered addresses published experimental data. The specific case considered addresses the effect of injection fluid composition. The predicted and the experimental data are shown to be in good agreement. This new model has a broader applicability in diagnosis, evaluation, and simulation of formation damage during drilling, production, and EOR processes. It can also be used to predict the performance of acidizing and other chemical flooding processes.

Introduction

When fluids are introduced into a porous rock during petroleum exploration and production, its original purpose is petroleum exploration and production, its original purpose is to increase the recovery of hydrocarbon. However, due to the incompatibility between injected and indigenous fluids, the change of reservoir rock properties can often be expected. The alteration of rock properties contributing to formation damage includes dissolution/precipitation of mineral grains, fine particles release and capture, and clay swelling. particles release and capture, and clay swelling. Previous modeling efforts in formation damage have addressed some aspects of the permeability reduction phenomena. The applicability of these models is limited to specific cases. Ohen and Civan (1990) developed a phenomenological model to account for fines migration and clay swelling during fluid flow through porous media. A parameter identification algorithm was utilized to porous media. A parameter identification algorithm was utilized to determine the best estimates of the system parameters using experimental data. In their model, the ionic concentration and pH effects on fines release and deposition were not considered. The rate of particle deposition and entrainment was assumed only hydrodynamically governed. Walsh et al. (1984) developed a geochemical model to simulate the reactive fluid flow in porous media. Their model requires detailed information about the chemical reactions occurring in the formation, and the particle movement in the porous structure was not considered. Rege (1985) and Rege and Fogler (1989) used network analysis to describe pore throat blocking mechanism by precipitates from chemical reaction. Network models demand a great deal of computational effort and also they do not take swelling of formation into consideration.

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