Polymer Solution Preparation and Quality Control at Milne Point

Abstract

This paper focuses on solution preparation and quality control activities associated with the Milne Point polymer flood on the North Slope of Alaska. This project uses ten different polymer injection locations with a variety of skid types and configurations, which had a notable impact on polymer quality control and dissolution operations. Compared with bulk 500-750-kg polymer bags, silos greatly improved the storage capacity and increased the overall quality of polymer wetting in system. Silos also required less physical effort when transferring polymer. Polymer hydration skids that were made inhouse by the polymer supplier were more reliable and experienced fewer polymer solution quality and startup issues than those that were outsourced. These inhouse skids also used a uniform programming software that made it relatively easy to train the operators on new hydration skids. For pumping polymer mother solution, triplex pumps provided the best run time and were most maintenance-friendly, compared with diaphragm or triple screw pumps. Although polymer solutions could be prepared that met our target viscosities without using a nitrogen blanket, corrosion and iron particulates raised substantial reliability and injectivity concerns if nitrogen blanketing was not used—especially when using black iron piping and when the make-up water contained dissolved iron. Inline static mixers were ineffective in mixing mother solution with dilution water when the mixing occurred close to the wellhead. Mixing the two streams too close to the wellhead led to substantial variations in wellhead viscosity measurements. Dedicating individual pumps for injection into a given well provided desirable flexibility in controlling rates and concentrations of polymer for the well. Monitoring produced salinity and polymer concentration provided useful insights about improved sweep and polymer retention associated with the polymer flood. The observed field behavior was consistent with laboratory studies indicating a "tailing" phenomenon associated with polymer retention at Milne Point.