Abstract
10 typical Surfactant-Polymer (SP) flooding field tests in China were reviewed to help understand the benefit and challenge of SP flooding in low oil price era. Among these 10 field tests, only 2 were very successful, the others were not as good as expected, while some are technically and economically unsuccessful. Although ASP flooding can make incremental oil recovery of 30% in large scale field tests in Daqing, the complex anti-scaling and emulsion breaking technology and thus high cost makes it less attractive. No alkali SP flooding was believed a developing trend of chemical flooding with a predicted incremental oil recovery more than 12%. In this paper, 10 large scale SP flooding field tests including one in offshore in China were critically compared and reviewed. Surfactants and its screening techniques were introduced. The problems of high injection pressure and difference to predicted incremental oil recovery were discussed. Although laboratory tests showed that SP flooding could make additional recovery of more than 15%, and the predicted incremental oil recovery was between 12% to 15.5%, only one SP flooding in Shengli made high incremental oil recovery of 16.8% upon water recovery of 36.3%. This field test was so successful that many enlarged field tests and industrial applications were carried out. However, none of them was in agreement with numerical simulation. The actual incremental recovery was in 1.3%-6.7%. Incremental oil recovery in post– polymer flooding reservoir in Daqing was 2.4%, less than the expected value 6.3%. Recently 3 of 5 field tests in Xinjiang, Jilin and Changqing was far from success. Three reasons may account for this. First, the surfactants adsorption in formation makes the ultra-low IFT duration not as long or far as expected, as verified from both laboratory and field test. Second, the injected polymer concentration and molecular weight was too high for the reviewed reservoir formation. SP field tests results in high permeability Liaohe reservoir was much better than the other 4 field tests in CNPC. Third, resent screen method and numerical simulation technique needs to be improved since most field tests results were in disagreement with them. It is high time to reevaluate the potential of SP flooding. It is high time to study how far the ultra-low IFT chemical system can flow in reservoirs. Low adsorption surfactants were the key to success for SP flooding. The alkali effect in ASP flooding should have been more emphasized and investigated.
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