Experimental Investigation and Simulation of Polymer Flooding in High Temperature High Salinity Carbonate Reservoirs

Polymer flooding is a well-established chemical enhanced oil recovery (EOR) technique. However, its application in High-Temperature and High-Salinity (HTHS) carbonate reservoirs remains a challenging task due to the unavailability of polymers that can withstand the harsh conditions. Identifying thermally stable, salt-tolerant polymers with high thickening efficiency and low adsorption in carbonate reservoirs will be a major step towards the successful application of polymer flooding in HTHS carbonate reservoirs.;This research is focused on unfolding the potential application of polymer flooding in carbonate cores under harsh conditions (120°C and 167 g/L). Based on extensive rheological and phase behavior analysis presented by Mr. Qadri Master Thesis "Polymers for EOR in High-Temperature, High-Salinity, Carbonate Reservoirs", 2015, a screened-out biopolymer, Schizophyllan, has shown the feasibility. It has potential resistance to HTHS condition for the targeted carbonate reservoir. This work has been evaluated for mobility control and hence improving oil recovery by performing series of coreflooding experiments. Various parameters including permeability, polymer slug size and initiation and their effects on final oil recovery are assessed. The experimental results and data analysis have shown that the employment of this biopolymer could offer additional 7-10% incremental oil recovery after waterflooding.;Simulation work has been carried out using CMG software to history-match unsteady state (USS) coreflooding experimental results. The advantages of this model are to predict polymer injection performance, optimize slug size and injection time, and to investigate capillary end effect on relative permeability curves before and after polymer injection. Simulation results confirmed that injecting 0.1 pore volume (PV) of polymer slug after 0.3 PV of waterflooding pre-flush would achieve the optimum oil recovery.;This work has demonstrated the potential advantage of the biopolymer for HTHS carbonate reservoir. In addition, the work also highlights the technical limitation of the selected biopolymer under an-aerobic conditions.