Colloid Retention and Flow in Porous Media

by
Shutong Pang, Ph.D.

University of Texas at Austin, 1996
Supervisor: M. M. Sharma

The transport and filtration of particulate suspensions in porous media is a process of considerable importance in science and engineering. Despite the great deal of work that has been done in this area two fundamental questions remain unresolved: the effect of solids concentration in the flowing suspension on particle trapping and the effect of previously deposited particles on the filtration coefficient. Both of these questions are addressed through Stokesian Dynamics simulation of particulate flow through porous media. Simulations are conducted to study the role of solids concentration as well as colloid size on the trapping efficiency of sphere packs. It is found that as the flowing particle concentration increases, hydrodynamic retardation of particles will cause the trapping efficiency to increase with particle concentration. This effect has never been quantified in the past. In addition to multi-particle simulations we also studied the effect of previously deposited particles on the filtration coefficient. Our results show that retained particles in porous media can significantly increase the rate of subsequent particle plugging. The evolution of the filtration coefficient with time is obtained.

The visco-elastic properties of highly concentrated suspensions have also been studied using a lattice model. Elastic moduli can be calculated from the model in terms of interparticle forces while the viscous part can be obtained from models available in the literature. The effects of various parameters on elastic moduli have been investigated. These parameters include particle size, concentration, surface potential, and solution ionic strength. Comparisons made with experimental data show good agreement with model predictions.

In addition to providing us with answers to the fundamental questions noted above the Stokesian Dynamics simulation results are used to obtain the transition time from internal to external filtration. The transition time is then used in a new model that incorporates both internal and external filtration developed for predicting well injectivity decline. The model also allows for various types of well completions and it can be used whether or not core flow test data is available. Based on the model, a well injectivity decline (WID) simulator has been implemented under a PC Windows environment. WID incorporated all the novel features that our model studies provide and it has a user friendly graphical interface. Test examples and field case studies show that WID can be used practically for predicting an injector's performance and for conducting what-if studies in designing water injection projects.

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