Lessons Learned From ASP Flooding Tests in China
Authors: Guo Hu , Li Yiqiang , Li Yanyue , Kong Debin , Li Binhui , Wang Fuyong 
Published: May 2017

Abstract
Although Alkali-Surfactant-Polymer (ASP) flooding enhance oil recovery (EOR) technique has been put forward many years ago, it was not until 2014 that it is first put into industrial application in Daqing Oilfield in China. Under such low oil price, ASP flooding advance in China provides confidence for ASP flooding as a chemical EOR technology. In 2014, ASP flooding entered into industrial application stage first time in history. Crude oil production from ASP flooding in 2015 and 2016 in Daqing Oilfield was 3.5million and 4 million ton, which accounts for the 9% and 11% total oil production respectively. In 2016, another large scale ASP flooding field test in high temperature (81 °C) reservoir in central was seen staged incremental oil recovery 7.7% in central well zone. 30 ASP flooding field tests in China were reviewed to help promote wiser use of this promising technology. ASP flooding in Daqing Oilfield deserves most attention. Strong alkali (NaOH) ASP flooding (SASP) was given more emphasis than weak alkali alkali (Na2CO3) ASP flooding (WASP) in a long time in Daqing, lower interfacial tension(IFT) of surfactant and higher recovery in presence of NaOH than Na2CO3 the most important reason. Other ASP flooding field tests finished in China are all Na2CO3 based, including one using mixture of NaOH and Na2CO3. With progress in surfactant production, a recent large scale WASP field tests in Daqing was seen incremental oil recovery of near 30%, higher than most previous SASP ones, and near to the most successful SASP one. However, this most successful SASP was partly attributed to the weak alkali factor. Recent studies shows that WASP incremental oil recovery factor could be as good as SASP but with much better economic benefits. According to Daqing Oilfield review, the equipment IFT is more determinant than dynamic IFT in contribution to displacement efficiency, thus it is better to choose lower dynamic IFT when equilibrium IFT met the 10-3 orders of magnitude requirement. However, it is impossible for many surfactants to form equilibrium IFT, thus dynamic minimum IFT was chosen as criteria. For low acid value Daqing crude oil, asphaltene and resin component plays a very important role in reducing oil/water IFT, and asphaltene is believed more influential, though more work are required to answer this controversial issue. Progress in surfactant production, overcoming of scaling and produced fluid handling challenger is the foundation of ASP industrial application. Dynamic adjustment in ASP flooding is common practice in Daqing. For the compatibility between ASP and formation pore structure, especially considering emulsion and formation damage, no satisfactory standards are found yet. Further work should be on emulsification effect in ASP flooding. Mixture of cation and anion surfactants used in Henan Oilfield may be a good choice to face the high temperature challenge. Ultra-high temperature reservoir ASP flooding with organic alkali is under investigation and a field test is in schedule. It is very difficult to carry out ASP flooding in high temperature and high divalent cation reservoir and no success was seen in such kind of reservoirs in China. According to one field test, EOR routine should be selected with consideration of residual oil type to decide whether to enlarge sweep volume or/and displacement efficiency. Micellar flooding failure in Yumen Laojunmiao (YM-LJM) reservoir makes subsequent field tests choose the "small concentration large slug" technical route instead of "high concentration small slug" one like YM-LJM. ASP flooding can increase oil recovery by 30% and control the cost below 30 US dollar/bbl, thus it can be used to face low oil price challenge.