Multiple Slug Scaling of Linear and Pattern Laboratory Chemical Floods

Abstract

Abstract The screening and design of chemical flood processes requires an understanding of the effects of each chemical slug on oil recovery. The concept of volumetric linear scaling can be extended to processes involving the injection of multiple chemical slugs as long as the relative ratios of slug sizes are held constant. This allows fast development of the relation between oil recovery and slug size requirements for each chemical injected based on only a few laboratory linear floods. Linear floods were conducted in a synthetic water-wet matrix. The multiple slug scaling approach used oil saturation distributions measured by microwave attenuation in one laboratory flood to predict accurately the tertiary residual oil saturation and tertiary oil breakthrough in another laboratory linear flood run with larger slug sizes. Oil saturation distributions at 0.11 V/Vp intervals during the flood, as well as at Sorc, were also accurately predicted. A laboratory quarter five-spot pattern flood involving sequential injection of a small surfactant slug, a small polymer slug, and continuous drive water was run in a water-wet synthetic matrix. Linear flood oil saturation distributions were scaled to predict the oil saturation distributions in the pattern using a fixed twelve streamtube model for the flow. Details of this scaling procedure are given. Residual tertiary oil saturation, tertiary recovery, and oil saturation changes with time were predicted to within the experimental errors involved in the procedures. The observed tertiary oil breakthrough was later than predicted. Observed oil saturation distributions tended to show more oil left in the corners of the model than predicted by the scaling theory. These secondary effects and the overall behavior of the pattern flood are considered in terms of the chosen streamtube network and the assumptions of stable unit mobility flow.