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How to Select Polymer Molecular Weight and Concentration to Avoid Blocking? Field Practices Experience
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2019 – 20th European Symposium on Improved Oil Recovery, Apr 2019, Volume 2019, p.1 - 15
Abstract
In current lasting low oil price era, polymer flooding is the most economical mature chemical EOR technique. Following our previous paper focused on theoretical aspect, lessons learned from onshore and offshore polymer flooding practice in China are summarized and reviewed to provide operational guidelines for engineers and insights for researchers. The previous paper ( Guo, 2017 ) focuses on theoretical aspect of polymer molecular cluster size and its blocking mechanisms with strata pore-throat, this paper gives practical aspect of polymer concentration and molecular weight (Mw) selection advice. Polymer flooding has been widely used commercially since 1996 and 1997 in Daqing and Shengli Oilfield, the largest two oilfields in China. Experiences and lessons from commercial polymer flooding practice in China are reviewed. Previous popular criteria in China may lead to blocking in low permeability strata. In addition, difficulty exists to select the proper core samples to represent the target strata. One common practice in Daqing selects the certain content permeability sublayer limit in accumulation curve from coring or logging. However, their blocking mechanisms may be improved. Interests in polymer viscoelasticity effect on displacement efficiency encourages to inject most viscous polymer. However, latest polymer flooding practice in Xinjiang Oilfield in China shows that serious blocking happens. When the concentration and polymer molecular was reduced, field test performance got better. If the injection pressure is high, the planned production volume will not be injected, and the liquid production will drop greatly. The damage of the oil wells and the damage of the injection equipment, as well as failure to inject polymer are signs of formation blockage.The practice of polymer flooding in Shengli Oilfield shows that for high permeability oil layers, the use of lower concentration and medium molecular weight polymers can achieve very good technical and economic effects.