A Novel Approach to Surfactant Flooding under Mixed-Wet Conditions, 2012.

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 higher 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. Separatemeasurement 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 heterogeneitiessmaller than the grid block. Reduced interfacial tension (IFT) by surfactant will alter local capillary
phase trapping andthereby change the effective multiphase properties.

One expected outcome from this activity is an effective CDCcurve for a heterogeneous flow unit, which will integrate the effects of both (i) increased efficiency on the corescale 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 andUTCHEM. Different interpretations of core experiments and the significance of upscaling in field displacements willbe evaluated.The project will answer if surfactant flooding has a potential outside the water-wet regime, and if so, indicate how tolocate 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