Study on the accessible pore volume coefficient of chemical flooding systems under different permeability, layer combination, and planar phase transition conditions

Abstract In this paper, first, the micro accessible efficiency of chemical flooding under different permeability reservoir conditions is studied by using nuclear magnetic resonance technology. Second, the macroscopic accessible efficiency of chemical agents under different types of sand body layer combinations was elucidated. Third, the macroscopic accessible pore volume correction coefficient of chemical agents under the phase transition conditions between injection and production wells was analyzed. Results show the following: (a) Permeability cannot be the only indicator for evaluating whether a reservoir is suitable for chemical flooding. (b) When the permeability grade ratio is less than 2.27 (10 −3 μm 2 /10 −3 μm 2 ), the correction factor for macroscopic accessible pore volume of chemical agents is 1.00; when the permeability grade ratio has increased to 3.33, the macroscopic accessible pore volume correction factor for chemical agents in non‐main sheet sand reservoirs is 0.68; and when the permeability grade ratio has increased to 16.67, the correction factor for macroscopic accessible pore volume of off balance sheet reservoir chemicals is 0.04. (c) The type and location of phase transition in sand bodies between injection and production wells have a significant impact on the macroscopic accessible volume coefficient of chemical agents. This part of the research is of great significance for selecting acid types based on reservoir properties.