Polymer flooding – Does Microscopic Displacement Efficiency Matter?

Abstract

Polymer flooding is an enhanced oil recovery (EOR) technique that aims to enhance the stability of the flood front in order to increase sweep efficiency and thereby increase hydrocarbon recovery. Polymer flooding studies often focus on large-scale sweep efficiency and neglect the impact of the pore-scale displacement efficiency of the multi-phase flow. This work explores the pore-scale behavior of water vs polymer flooding, and examines the impact of rock surface wettability on the microscopic displacement efficiency using digital rock physics. In this study, a micro-CT image of a sandstone rock sample was numerically simulated for both water and polymer flooding under oil-wet and water-wet conditions. All simulations were performed at a capillary number of 1E-5, corresponding to a capillary dominated flow regime. Results of the four two-phase flow imbibition simulations are analyzed with respect to displacement character, water phase break-through, viscous/capillary fingering, and trapped oil. In the water-wet scenario, differences between water flood and polymer flood are small, with the flood front giving a piston-like displacement and breakthrough occurring at about 0.4 pore volume (PV) for both types of injected fluid. On the other hand, for the oil-wet scenario, water flood and polymer flood show significant differences. In the water flood, fingering occurs and much of the oil is bypassed early on, whereas the polymer flood displaces more oil and thereby provides better microscopic sweep efficiency throughout the flood and especially around breakthrough. Overall the results for this rock sample indicate that water flood and polymer flood provide similar recovery for a water-wet condition, while the reduced mobility ratio of polymer flood gives significantly improved recovery for an oil-wet condition by avoiding the onset of microscopic (pore-scale) fingering that occurs in the water flood. This study suggests that depending on the rock-fluid conditions, the use of polymer can impact microscopic sweep efficiency, in addition to the well-known effect on macroscopic sweep behavior

Towards Multiscale Digital Rocks: Application of a Sub-Resolution Production Model to a multiscale Sandstone

“…The fluid flow numerical simulation approach used in this study is the Lattice Boltzmann method (LBM), which has been extensively used in digital rock applications, as a direct simulation approach for resolvable pore-scale events and capturing physical properties, such as residual oil on wettability dependence scenarios, capillary number effects and viscous fingering phenomena [11,[15][16][17][18]. The LBM is based on the kinetic equation, and represents a statistical description of the molecular behavior of fluid particles.…”

Nuevas tecnologías de recobro químico y su aplicabilidad en yacimientos colombianos

“…Los polímeros utilizados en procesos de recobro mejorado son, mayormente, las poliacrilamidas parcialmente hidrolizadas (HPAM) y sus derivados (Seright, 2016;Albonico & Lockhart, 1993;Lizcano-Nino et al 2020). La HPAM posee propiedades importantes (hidrofílica y soluble en agua, incrementa la viscosidad del agua, entre otras) que la hacen un buen candidato para procesos EOR; sin embargo, presenta limitaciones en su rendimiento en condiciones de alta temperatura y salinidad, donde las moléculas del polímero pueden configurarse de forma aleatoria y generar una disminución significativa de la viscosidad (Wu et al, 2012;Albonico & Lockhart, 1993;Molano, et al 2014;Pinto, M. S. et al 2018;Sun G, et al 2018).…”