Chapter 1 - Supplement and optimization of classical capillary number experimental curve for enhanced oil recovery by combination flooding

Abstract

In the middle of the last century, American scientists put forward the concept of capillary number and obtained the relation curve between capillary number and residual oil through experiments. These experiments revealed that as capillary number increases, the corresponding residual oil saturation decreases, and after capillary number reaches a limit, the residual oil saturation becomes stable and no longer decreases. These important achievements laid a theoretical base for enhanced oil recovery with chemical flooding. On the basis of the theory, scholars developed UTCHEM, a chemical flooding numerical simulation software. During their numerical simulation study of combination flooding, the authors found that as capillary number increases to greater than the limit capillary number, the changes of the residual oil saturation along with the capillary number differ from the classical capillary number curve. Oil displacement experiments prove that there are defects in the classical capillary number experimental curve. The capillary number “calculation” curve is obtained with a method of numerical simulation, and a complete description of capillary number curve is provided. On this basis, combination flooding capillary number experimental curve QL is obtained, which is different from the classical capillary curve. Based on this, an expression of corresponding combination flooding relative permeability curve QL is given and the corresponding relative permeability parameters are determined with experiments. Further oil displacement experiment research recognizes the cause of the singular changes of the capillary number curve. “Combination flooding capillary number experimental curve QL” and “combination flooding relative permeability curve QL” are written incombination flooding software IMCFS, providing an effective technical support for the application of combination flooding technical research.