Recent Advancements in Viscoelastic Polymer Flooding EOR Applications in Carbonates and Sandstones

Abstract

Abstract Polymer flooding is a well-established chemical enhanced oil recovery (CEOR) technique that effectively improves oil recovery after waterflooding. Due to a large number of studies conducted in this area and extensive field data availability, this technique has gained solid practical and theoretical knowledge. Conventionally, the polymer injection is believed to increase volumetric sweep efficiency by producing movable oil that is remained unswept after waterflooding. Nevertheless, studies demonstrated that specific viscoelastic polymers might also mobilize residual oil and improve microscopic displacement efficiency, in addition to macroscopic sweep efficiency. Although polymer flooding is an extensively applied CEOR technique in sandstones, its applicability in carbonates is still limited. This is related to the prevailing complicated conditions in carbonates including mixed-to-oil wettability nature, high heterogeneity with low permeability, and harsh conditions of high temperatures (above 85°C), high salinity (above 100,000 ppm), and high hardness (above 1,000 ppm). Recently, new polymers have been developed to overcome the challenges of harsh conditions in carbonates. These novel polymers incorporate specific monomers that protect the polymer from thermal and chemical degradations. However, the viscoelasticity of these synthetic polymers and their effect on oil mobilization are not yet comprehended and requires further investigation and research. In this paper, we review the recent studies conducted on viscoelastic polymer flooding in sandstones and carbonates. The article describes viscoelastic polymer recovery mechanisms, polymer viscoelastic properties and the factors controlling them, and the effect of viscoelastic polymers on residual oil mobilization. This study also provides insights into the challenges faced during viscoelastic polymer flooding operations as well as field applications in sandstone and carbonate reservoirs.