Present Status of Research and Application of Chemical Combination Flooding Technique and its Future

Abstract

Chemical combination flooding technique is one of EOR techniques. The current status of chemical combination flooding including EOR mechanism, formula study, field test and application have been introduced and discussed. The problems met in field tests and future development trend of chemical combination flooding are directed. Synergistic effect among alkali, surfactant and polymer in ASP combination flooding, can improve both displacing efficiency and swept efficiency due to the increase of viscosity of displacing liquid and decrease in interfacial tension between oil and water. Emulsion ability of the chemical combination system can also improve the displacing efficiency. In addition, viscoelasticity of the combination system is also beneficial to improve the displacing efficiency. There are two main research tendencies for the formula system of chemical combination flooding. One is the high concentration small slug size system leaded by U.S., which can get high oil recovery but the cost is high. The other is a low concentration large slug size system leaded by China, which has good results and relatively low cost. With recent development of new polymers and surfactants, the chemical combination flooding has been will be widely used in different reservoirs. Pilot tests of ASP flooding in China have increased the oil recovery significantly. And such process has been extended to industrial tests and application. A serial of technologies has formed during ASP flooding field tests. Two main problems are shorter pump-checking period and higher cost of produced liquid handing. In order to avoid the negative effect of alkali, SP flooding pilot tests have been deployed. The general trend of chemical combination flooding technique is changing from strong-alkali ASP flooding to weak-alkali ASP flooding and alkali-free SP flooding. The application target reservoirs have extended from integral sandstone reservoirs to conglomerate reservoirs, complicated fault block reservoirs and carbonate reservoirs, from low temperature and low salinity reservoirs to high temperature and high salinity reservoirs.