Recent Developments in Polymer Flooding for Carbonate Reservoirs under Harsh Conditions

Polymer flooding is one of the well-established and commercially-available techniques for enhanced oil recovery in the petroleum industry. It is the most widely adopted chemical enhanced oil recovery technique in sandstones, but its application in carbonates is limited due to the harsh reservoir conditions of high temperature, high salinity, and low permeability. However, research is advancing to expand the applicability of this technique to carbonate reservoirs in a cost effective manner. In this paper, we present a comprehensive review on polymer flooding for carbonates under harsh conditions. This review includes descriptions of underlying mechanisms, polymer types, polymer screening studies, coreflood laboratory work, numerical and modeling works, and field applications. Screening of new polymers for potential field applications is also discussed. In addition, polymer rheology and challenges posed to polymer flow in the porous media are described. Moreover, summary tables of different monomers used to tailor polymers for harsh conditions as well as temperature and salinity limits of different polymers are provided, which makes this review as a guidance for implementing new projects using the polymer flooding technique. The literature review conducted shows that with the recent technology, a field-scale application of polymer flooding in carbonate reservoirs is possible. Several polymer types have been recently developed to overcome harsh carbonate conditions of high temperature, high salinity, and low permeability. This is encouraging towards conducting pilots in carbonate reservoirs in a cost effective manner. At the end of this paper, recommendations to overcome the challenges of high temperature, high salinity/hardness, and poor injectivity are provided based on this vast literature review and our experiences in polymer flooding. This paper gives more insight into polymer flooding aspects and its different applications in the oil industry. In addition, the study is considered as a guide for starting or implementing potential projects on polymer flooding in carbonate reservoirs under harsh conditions.