Recent Advances of Polymer Flooding in China

Abstract

Abstract Polymer flooding is one of the most promising chemical enhanced oil recovery (EOR) techniques which have high incremental oil recovery factor (IORF), low cost and wide reservoir applicability. The first field test of polymer flooding was reported in the United States in 1960s. The first large commercial polymer flooding in China started in Daqing oilfield, which has been remained the largest application in the world. However, encouraged by the conventional field applications and new findings of polymer's viscoelasticity effect on residual oil saturation (ROS) reduction, some high concentration high molecular weight polymer flooding (HCHMW) field tests have been conducted and reported. Although some field tests were well documented, subsequent progress was seldom reported. According to a recent review of latest polymer flooding projects in China, it is found that HCHMW have only very limited application in Daqing. This is not in agreement with the expectations especially that viscoelastivity of synthetic partically hydrolyzed polyacrylamide (HPAM) is drawing much attention recently. This paper explains why HCHMW is not widely used at present. Different opinions on polymer's viscoelasticity effect on ROS reduction are also critically reviewed. Other field progress of salt-tolerance polymer flooding tests and new amphiphilic polymer tests in Daqing were summarized. Associative polymer (APs) commercial application in offshore reservoirs and some new polymers used in China were also involved. Risk of high polymer injection pressure, optimum viscosity ratio, blocking mechanism, and capillary number theory are discussed. Learnings from many polymer flooding field applications has been given. In the end, quaternary recovery practices in post-polymer flooding reservoirs were compared. This paper helps to clarify some misleading ideas in polymer flooding implementations based on theory and practices of polymer flooding in China.