Mobility Control Design for Miscible-Type Waterfloods Using Micellar Solutions

Abstract

Introduction Oil recovery in any flooding operation depends on unit displacementefficiency and on the reservoir volume affected by the displacing fluid. Miscible fluids are used to increase the unit displacement efficiency. A higherpercentage of reservoir pore volume can be contacted if there is adequatemobility control during flooding. With hydrocarbon displacement media such as dry gas, enriched gas, and LPGslug, viscosity determines the mobility control. Under secondary recoveryconditions, viscosity ratios generally are greater than one, and theunfavorable mobility condition leads to a poor conformance factor. Both oil and water are displaced in a miscible waterflood. The flowing oiland water establish the mobility requirement for the displacing system. As weshall discuss later, the total mobility can be determined from relativepermeability curves. With tertiary flooding, transient test results can behelpful in selecting representative relative permeability curves. As will alsobe described, laboratory flooding procedures can be used to measure totalmobility directly. In miscible waterflooding such as with the alcohol slug process, there canbe a loss of miscibility because of mixing. The lack of mobility control behindthe alcohol slug has not been studied extensively. A new recovery process isavailable that utilizes micellar solutions for miscible-type waterflooding. With this process, mobility control is possible over a wide range of reservoirvariables. The mobility control feature, along with effective unitdisplacement, insures a high over-all recovery of oil. Design criteria foradequate mobility control in the process are described in this paper.