Fundamentals of Microgel Flooding and Nanoparticles-Stabilized Foams in Enhanced Oil Recovery

Abstract

For centuries oil has remained a critical energy source for human civilization. After years of extraction, many oil fields have reached or are reaching a decline stage of production, even though up to a half of the total crude oil reserves in these fields has not been recovered yet. One reason is due to the structural heterogeneity of the oil reservoirs—reservoirs may consist of regions of higher permeability with larger pore size and regions of lower permeability with smaller pore size. Displacing fluids tend to flow through large permeability zones only without reaching the oil trapped in low permeability region; this poor sweep efficiency results in low oil recovery rate and excessive water production. Among various enhanced oil recovery (EOR) technologies, preformed particle gel (PPG) treatment and foam flooding are commonly used and can both effectively improve the sweep efficiency. The performance of these EOR technologies depends on a number of geometrical, materials, and flow properties that can be measured or controlled. However, the relation between the large-scale performance and the controllable or measurable quantities remains poorly understood. Another challenge to be addressed in EOR foam flooding is implementing long-term stability of the foams against coarsening and coalescence. This dissertation addresses these critical issues in PPG treatment and foam flooding from two aspects. First, we investigate the transport of soft spherical particles through porous media at both pore scale and macroscale and develop a generalized capillary bundle model to quantitatively correlate the overall pressure drop and permeability reduction with the concentration and mechanical property of microgels, the size ratio of microgel to pore throat, and the flux. Second, we produce monodisperse nanoparticles-stabilized foams and characterize their morphology, stability, and rheology; these foams exhibit long-term stability and much higher storage and viscous moduli than surfactant-stabilized foams. Besides the application in EOR, this work can also potentially benefit other processes and industries such as particle transport in soils or aquifers, food, cleaning, and personal care products