Effects of Core Size and Surfactant Choice on Fluid Saturation Development in Surfactant/Polymer Corefloods

Surfactant/polymer flooding allows for a significant increase in oil recovered at both laboratory and field scales. Limitations in application at the reservoir scale are, however, present and can be associated with both the complexity of the underlying displacement process and the time-intensive nature of the up-scaling workflow. Pivotal to this workflow are corefloods which serve to both validate the extent of oil recovery and extract modeling parameters used in upscaling. To enhance the understanding of the evolution of the saturation distribution within the rock sample, we present the utilization of X-ray computed tomography to image six distinct surfactant/polymer corefloods. In doing so, we visualize the formation and propagation of an oil bank by reconstructing multidimensional saturation maps. We conduct experiments on three distinct core sizes and two different surfactants, an SBDS/isbutanol formulation and an L-145-10s 90 formulation, in order to decouple the effect of these two parameters on the flow behavior observed in situ. We note that the oil production post oil bank breakthrough is primarily influenced by the surfactant choice, with the SDBS/isobutanol formulation displaying longer tailing production of a low oil cut. On the other hand, the core size dominated the extent of self-similarity of the saturation profiles with smaller cores showing less overlap in the self-similarity profiles. Consequently, we highlight the difference in applicability of a fractional flow approach to larger and smaller cores for upscaling parameter extraction and thus provide guidance for corefloods where direct imaging is not available

Thermoresponsive Block Copolymer Core–Shell Nanoparticles with Tunable Flow Behavior in Porous Media

With the purpose of investigating new polymeric materials as potential flow modifiers for their future application in enhanced oil recovery (EOR), a series of amphiphilic poly(di(ethylene glycol) methyl ether methacrylate-co-oligo(ethylene glycol) methyl ether methacrylate) [P(DEGMA-co-OEGMA)]-based core–shell nanoparticles were prepared by aqueous reversible addition–fragmentation chain transfer-mediated polymerization-induced self-assembly. The developed nano-objects were shown to be thermoresponsive, demonstrating a reversible lower-critical solution temperature (LCST)-type phase transition with increasing solution temperature. Characterization of their thermoresponsive nature by variable-temperature UV–vis and dynamic light scattering analyses revealed that these particles reversibly aggregate when heated above their LCST and that the critical transition temperature could be accurately tuned by simply altering the molar ratio of core-forming monomers. Sandpack experiments were conducted to evaluate their pore-blocking performance at low flow rates in a porous medium heated at temperatures above their LCST. This analysis revealed that particles aggregated in the sandpack column and caused pore blockage with a significant reduction in the porous medium permeability. The developed aggregates and the increased pressure generated by the blockage were found to remain stable under the injection of brine and were observed to rapidly dissipate upon reducing the temperature below the LCST of each formulation. Further investigation by double-column sandpack analysis showed that the blockage was able to reform when re-heated and tracked the thermal front. Moreover, the rate of blockage formation was observed to be slower when the LCST of the injected particles was higher. Our investigation is expected to pave the way for the design of “smart” and versatile polymer technologies for EOR applications in future studies