Abstract
Surfactant–polymer (SP) flooding has significant potential to enhance oil recovery after water flooding in mature reservoirs. However, the economic benefit of the SP flooding process is unsatisfactory under low oil prices. Thus, it is necessary to reduce the chemical costs and improve SP flooding efficiency to make SP flooding more profitable. Our goal was to maximize the incremental oil recovery of the SP flooding process after water flooding by using the equal chemical consumption cost to ensure the economic viability of the SP flooding process. Thus, a systematic study was carried out to investigate the SP flooding process under different injection strategies by conducting parallel sand pack flooding experiments to optimize the SP flooding design. Then, the comparison of the remaining oil distribution after water flooding and SP flooding under different injection strategies was studied. The results demonstrate that the EOR efficiency of the SP flooding process under the alternating injection of polymer and surfactant–polymer (PASP) is higher than that of conventional simultaneous injection of surfactant and polymer. Moreover, as the alternating cycle increases, the incremental oil recovery increases. Based on the analysis of fractional flow, incremental oil recovery, and remaining oil distribution when compared with the conventional simultaneous injection of surfactant and polymer, the alternating injection of polymer and surfactant–polymer (PASP) showed better sweep efficiency improvement and recovered more remaining oil trapped in the low permeability zone. Thus, these findings could provide insights into designing the SP flooding process under low oil prices.
Highlights
Water flooding is recognized as an important secondary recovery method because it is economically advantageous for the development of oil reservoirs
The results demonstrate that the EOR efficiency of the SP flooding process under the alternating injection of polymer and surfactant–polymer (PASP) is higher than that of conventional simultaneous injection of surfactant and polymer
Based on the analysis of fractional flow, incremental oil recovery, and remaining oil distribution when compared with the conventional simultaneous injection of surfactant and polymer, the alternating injection of polymer and surfactant–polymer (PASP) showed better sweep efficiency improvement and recovered more remaining oil trapped in the low permeability zone
Summary
Water flooding is recognized as an important secondary recovery method because it is economically advantageous for the development of oil reservoirs. With the maturity of a water flooded oil reservoir, due to the existence of a thief zone, the phenomenon of injected water channeling occurs, resulting in poor sweep efficiency and low ultimate oil recovery. With the increasing demand of crude oil consumption, it is of vital importance to develop more effective techniques to enhance oil recovery in mature water flooding reservoirs. Chemical enhanced oil recovery (CEOR) processes have demonstrated great potential for recovering more remaining oil in mature reservoirs after water flooding [1]. Polymers can increase the viscosity of the injected water phase and reduce the mobility ratio between water and oil, improving the sweep efficiency. By reducing the oil–water interfacial tension, Energies 2019, 12, 3789; doi:10.3390/en12193789 www.mdpi.com/journal/energies
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