Chemical enhance oil recovery(EOR) like polymer flooding and Alkaline-Surfactant-Polymer(ASP) flooding have been applied throughout the world for more than 20 years. However, few large-scale successes with these processes have been reported, except in China. To date, polymer flooding has been successfully applied industrial scale in Daqing since 1996. Polymer flooding alone contributed more than 10 million tons of oil in 2006, which occupied 25% yearly rate of Daqing. Incremental oil recoveries of up to 14% of OOIP have been obtained in the field. Much experience and lessons have been learnt on large scale polymer flooding including: major factors that influence the recovery and methods to increase the recovery; measures to obtain a uniform polymer injection profile; and how to lower the costs of polymer flooding. Also Daqing performed researches on other chemical floods application, such as surfactant flood, micellar-polymer flooding(MP), alkaline flooding, alkaline-surfactant-polymer flooding(ASP), alkaline polymer flooding(AP), ASP-foam, especially ASP. Those chemical floods were field tested or are testing to increase oil recovery, to study the feasibility, to provide technical and practical experience for expanding, and to find suitable post-polymer flooding enhanced oil recovery EOR technology. Through tests, the injectivity and productivity of ASP systems, the best technique of artificial lift and stimulation measures for low efficiency wells, chromatographic separation analysis in condition of different well spacing, and economic analysis of chemical EOR were all studied. Pilot test results showed that over 20% OOIP recovery can be obtained over that of waterflooding, and is both technically and economically feasible. Overall, experiences and lessons learned in field applications of chemical floods in Daqing are extremely valuable not only for expanding chemical EOR to other areas of Daqing, also for other countries. Introduction In order to satisfy the rising demand for energy because of China's spectacular economic growth, attention is all along being paid to the enhanced oil recovery(EOR) techniques as a method of obtaining more oil from the existing oilfields, because they know increasing oil and gas recovery from existing mature fields is still one of the most promising ways to increase supply, and also because of difficulty to find new giant oilfield in China. In order to increase oil recovery and stabilize oil production, the study on enhanced oil recovery techniques in Daqing have been carried out for more than 20 years. Now, notable progress has been made in chemical flooding. Industrial scale polymer flooding in Daqing started in 1996, the annual oil production rate by polymer flooding in Daqing has exceeded 10 million tons, which occupied more than one fourth of total output of Daqing(Wang et al. 2006). Also a biopolymer(Xanthan gum), which can be used under the conditions of high temperature(80 °C) and high salt concentrations(170,000 ppm), was developed(Han et al. 1999). In order to further increase oil recovery and to find the better substitute EOR technique for post-polymer flooding, the study on other types of chemical flooding, such as surfactant flooding, micellar-polymer flooding(MP), alkaline flooding, alkaline/surfactant /polymer(ASP), alkaline polymer(AP), ASP-foam, especially ASP, was also performed and ten ASP pilot test have been conducted with different well spacings, pay zones and at different blocks. The pilot tests of ASP have been conducted successfully, and results showed that more than 20% OOIP oil recovery were obtained over that of waterflooding. This paper will give a review of recent development of pilot test and industrial scale application of chemical flooding in Daqing, especially during last decade.
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