Mathematical modelling of fines migration in oilfield.
Phillip Lemon and Ibrahim Shahin
Engineering Honours Degree 2009
University of Adelaide
Fines migration in oilfields is an important detrimental and possibly beneficial aspect of oil production, primarily in reservoirs that are poorly consolidated, contain heavy oil or significant amounts of mobile clays. The migration of fines is caused by the hydrodynamic forces of lift and drag acting on a fine particle overcoming the forces that adsorb the particle to the surface of the grains. This occurs in the drainage zone of a well, with the migration of released fines typically causing a decline in the productivity of the well.
The primary goal of this project was to construct a mechanistic mathematical model for the release and subsequent capture of fines in a porous medium. The forces acting on a fine particle in a pore space were considered and mathematical descriptions of them taken from literature. A force balance on a fine particle was calculated to determine the most likely mechanism for the release of a particle from a pore wall and the dependence of particle release on velocity. A segmented bundle-of-tubes model was then used to relate the pore scale mechanics to the macroscopic scale and to find a relationship between the concentration of retained particles and the superficial velocity of fluid through the porous medium. Expressions for the alteration of permeability as a function of the concentration of adsorbed and strained particles were also investigated.
The above models were used, in conjunction with deep bed filtration and Buckley- Leverett displacement theory, to develop a basic description of how fines migration could be used as an EOR method to improve the sweep efficiency of a waterflood. The analysis showed the potential for increased oil recovery from such a process but this work has yet to be verified by experimental data.