Cellulose Nanocrystal Stabilized Emulsions for Conformance Control and Fluid Diversion in Porous Media

Abstract

Abstract Nanoparticle stabilized emulsions have drawn increasing attention for applications in various industries including enhanced oil recovery (EOR). Unlike surfactants, nanoparticles provide long-term stability to the emulsions and significantly higher viscoelastic response. However, the flow behavior of nanoparticle stabilized emulsions in porous media has not been explored much. Cellulose Nanocrystals (CNCs) have gained attention in the past few years since they are an abundant renewable biomass-derived material. This study investigates the flow behavior and stability of oil in water emulsions stabilized by CNCs in unconsolidated porous media and the application of these emulsions in EOR and conformance control. Confocal Microscopy coupled with Cryo-SEM enabled us to precisely characterize the emulsion microstructure and correlate it to the rheological behavior of the emulsions. The rheological measurements revealed that a strong droplet network forms within the emulsions over time. Importantly, we show that the same network forms when the emulsions occupy pore space in a granular material. Emulsions were injected through a sandpack with a porosity of 35% and average pore diameter of 54 μm. The injected emulsions were aged inside the porous media for 24 hours. Thorough experimental assessment of the collected effluent samples revealed that the emulsion was stable. The porous medium was then subjected to a gradually increasing pressure gradient of either water or oil. Gradients greatly exceeding typical near-well values (>300 psi/ft) were required to establish flow, and the resulting flow rate exhibited a pressure gradient three orders of magnitude higher than in an untreated water saturated sandpack. Interestingly, a significantly larger gradient was needed for water to flow than for oil, raising the possibility of using this class of emulsions for selective phase blocking, and perhaps as relative permeability modifiers. Moreover, emulsions stabilized with other material allowed water to flow at very small gradients, confirming that the network formation is critical for this application. This study revealed the potential application of a naturally occurring biodegradable nanomaterial for conformance control and for curbing excessive water production where zonal isolation is difficult to achieve.