Application of Biopolymer to Improve Oil Recovery in High Temperature High Salinity Carbonate Reservoirs

Abstract

AbstractPolymer flooding is a well-established chemical enhanced oil recovery (EOR) technique. However, its application to 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. The potential biopolymer "Schizophyllan" is identified and its rheological properties are investigated. The effect of temperature and salinity on the behavior of the polymer solution is analyzed. In addition, the mechanical and long-term thermal stability of the polymer solutions and their adsorption on synthetic carbonate cores are also discussed.The tested polymer showed temperature stability and salt tolerance with no decrease in viscosity up to a temperature of 135 °C and 220 g/L salinity. The thermal stability and salt tolerance of the biopolymer are attributed to the non-ionic nature and the triple helical structure. Moreover, the polymer solution showed no decrease in viscosity when kept at 120 °C under anaerobic conditions for over eight months. A series of coreflooding experiments have been performed at reservoir temperature (120 °C) and salinity (167 g/L) to evaluate the performance of the polymer EOR process in carbonate reservoirs. Various parameters including reservoir permeability, polymer slug size and the initiation time of polymer EOR process are varied in this study in order to determine the optimum flooding conditions. Dynamic adsorption of the polymer on rock surface is also quantified and found to be very low in magnitude. Coreflooding results of polymer EOR using the potential biopolymer offered encouraging results with a range of incremental recoverable oil between 7-10% after waterflooding. Further research is still required on application of biopolymers on reservoir cores.