Predictability of Formation Damage by Modeling Chemical and Mechanical Processes

Abstract

Abstract A phenomenological model for formation damage by chemical and mechanical processes in petroleum reservoirs is presented. (Geochemical reactions involving dissolution/precipitation presented. (Geochemical reactions involving dissolution/precipitation and ion exchange are modeled. The precipitates are considered mobile and mixed with formation particles to contribute to the pore throat plugging. Size distribution of both precipitates and clay fines is represented by a bimodal distribution function. A semi-empirical approach is used to estimate the fraction of the plugged pore throats. The model parameters are determined through an optimization method by matching the model predictions to laboratory core test data. The capability and validity of the model are demonstrated by comparing the predictions obtained from this model with experimental data for four cases. The predicted and the experimental data are shown to be in good agreement in each case. This model can be used for diagnosis, evaluation, and simulation of damage and alteration of reservoir formation during drilling, production, and chemical flooding processes. Introduction Fluids introduced into petroleum bearing formation frequently cause formation damage due to the incompatibility between injected and indigenous fluids, and the mineral constituents of the formation. The alteration of rock properties contributing to formation damage includes dissolution/precipitation of mineral grains, fine particles release and capture, and formation swelling. Previous modeling efforts in formation damage have addressed some aspects of the permeability impairment phenomena. The applicability of these models is limited to specific cases. Ohen and Civan developed a phenomenological model to account for fines migration and clay swelling during fluid flow through porous media. 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 particle deposition and entrainment was assumed only hydrodynamically governed. Walsh et al. 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 and Fogler used a network analysis to describe the pore throat blocking mechanism by precipitates from chemical reactions. Network models demand a precipitates from chemical reactions. Network models demand a great deal-of computational effort. Walsh et al. and Rege and Fogler models do not take swelling of formation into consideration. This paper presents a comprehensive phenomenological model to simulate the permeability alteration mechanisms caused by various physical and chemical interactions between fluids and reservoir rocks. The model uses pseudocomponents for the chemical species existing in the system. The species with similar chemical properties are grouped together to form pseudocomponents. Therefore, there are less equations to be pseudocomponents. Therefore, there are less equations to be solved. But the model can satisfactorily simulate formation damage in most cases. The chemical reactions considered in this model include dissolution/precipitation of minerals, and cation exchange. P. 293