A novel approach to surfactant flooding under mixed-wet conditions

Traditionally, surfactant flooding has been a method for reducing residual oil after water flooding (Sorw), i.e. the target is oil trapped by capillary forces at pore scale. Field remaining oil saturation after water flooding (ROS) may be substantially hi gher than Sorw. The focus will be on ROS rather than Sorw as the target for surfactant flooding. The dependency of involved mechanisms on the wetting properties will be investigated. 1. CDC will be measured on cores at various wetting conditions. Separate measurement of capillary pressure curves will define wettability and be used to correct CDC for end-effects using in-house software tools. 2. Relative permeability curves will be measured at each wetting state, first without and then with surfactant. All curves will be corrected for end effects and compared. 3. Upscaling of measured multiphase properties to field simulation scale will include effects of heterogeneities smaller than the grid block. Reduced interfacial tension (IFT) by surfactant will alte r local capillary phase trapping and thereby change the effective multiphase properties. One expected outcome from this activity is an effective CDC curve for a heterogeneous flow unit, which will integrate the effects of both (i) increased efficiency on the core scale and (ii) heterogeneity of the flow unit. The observed differences will be documented and analyzed. 4. The field potential for surfactant flooding will be studied using reservoir simulation tools like Eclipse and UTCHEM. Different interpreta tions of core experiments and the significance of upscaling in field displacements will be evaluated. The project will answer if surfactant flooding has a potential outside the water-wet regime, and if so, indicate how to locate the best field candidates for which surfactant injection will be beneficial. 5. The criteria for selection of surfactant systems and procedure for qualification of these systems for mixed-wet reservoirs will be presented