Publications

CNOOC is performing a Polymer Flooding as a tertiary recovery method by adding high-molecular-weight polyacrylamide into injected water, so as to increase the viscosity of fluid, improve volumetric sweep efficiency, and thereby further increase the oil recovery factor. For the particular system at Widuri-C, the combination of free oxygen and ferric ions is apparently problematic in causing oxygen free-radical degradation of polymer-flood polymers. The viscosity was fluctuating and dependent on the water quality of produced water. CNOOC team and manager are working together with Starborn Chemical Company to overcome the problem aiming to deliver a required stable viscosity for polymer flooding project at WIDC-27. Laboratory study conducted to simulate chemical treatment for process water as well as its effect on polymer solution's viscosity. Based on laboratory study combination of Buffer Additive S-9363 and Iron Remover S-9119 could provide a persistent viscosity for given polymer solution. Successful field application has been acknowledged to maintain the viscosity of injected polymer at 20 mPa.s, even though higher dosage shall be introduced due to several limitations of polymer processing facilities. Combination of 150 ppm Iron Remover and 100 ppm of buffer additive could maintain the liquid viscosity at range 600-700 mPa.s. However, there is still strong possibility for improvement and dosage optimization by necessary modification requiring installation of inline mixers in process water lines and filtration unit prior the polymer solution injection into the injection well. Last but important is strong influence indicated during the chemical treatment with decreasing trend of water cut in WIDC-16 producer well compared with period before chemical treatment took place.