The Development of a Low-Shear Valve Suitable for Polymer Flooding

Abstract

Summary Hydrolyzed polyacrylamides (HPAMs) are used as mobility-control agents to improve the macroscopic sweep efficiency of oil reservoirs. To maximize their viscosifying power, very-high-molecular-weight (MW) polymers are preferred, which in turn make them very sensitive to shear degradation. Shear degradation originates from chain stretching and breaking when the solution is subjected to a sudden acceleration. Fundamental development work is presented, where polymer degradation is studied in flow through reducers and expanders of various geometrical shapes, as well as through straight pipes and pipe coils of various diameters and lengths. The work also demonstrates that the creation of pressure drop through viscous pipe friction is very ineffective with regular tubes, most likely because of the drag-reducing effect of polymer. In addition, the arrangement of very long, straight, or coiled pipes in parallel is impractical and bulky. This paper further presents the development of a novel valve technology that solves these challenges. First, through the unique use of spiraling flow channels with optimally designed reducer and expansion zones, machined on the surface of disks, shear forces and thereby polymer degradation is controlled. Second, by arranging numerous such disks to form a disk stack, any target capacity can be met efficiently. Third, the disk-stack concept enables an easy and reliable plug-based solution for flow regulation and control. The performance of the new valve technology is demonstrated through small- and large-scale prototype tests. At very-shear-sensitive test conditions, it is demonstrated that polymer degradation of the new valve is less than 10% at 40- to 45-bar pressure drop, compared with 60 to 80% for a standard valve.