Theoretical and experimental study of particle movement and deposition in porous media during water injection

Abstract

The flow of particulate suspensions and brines in porous media is encountered in a wide range of industrial situations such as oil production, soil erosion, and ground water pollution and in the operation of filter beds. Three major classes of such problems are addressed in this paper, namely particle movement, deposition and filtration. Particle movement and deposition are known to be serious problems in oil reservoirs where incompatible brine is brought into contact with the formation. Dramatic reductions in permeability are observed in such cases due to the release of fine particles that subsequently plug flow channels downstream. An experimental investigation was undertaken to look into the possible causes of the injectivity loss in a typical Iranian oilfield. Glass bead and sand beds were used to study the general behavior of fine particle movement and deposition in porous media. The experiments were conducted with injection rates from 12.5 to 200 cm 3/min. Aluminium oxide particles were suspended in the injected water to simulate fine particle migration in porous media. The particles were injected at concentrations ranging from 15 to 2000 ppm. It was observed that the build-up of flow resistance was mostly due to frontal face plugging. In subsequent experiments, aluminium oxide particles were added to the glass beads to study the effect of particles initially present in the glass bead pack. A mathematical model is presented that simulates the porosity impairment by particle movement and deposition. This model is based on the mass balance of particles flowing through the porous medium, and predicts the initial porosity and subsequently its reduction with time. The equations are relatively general and can be used to model the permeability reduction for any given pore or particle size distribution.