New Progress and Challenges of Chemical Combination Flooding in China

Abstract

Chemical combination flooding (CCF) is a greatly-enhanced-oil-recovery technique, which is developed on the basis of single chemical flooding such as polymer flooding, surfactant flooding, alkali flooding. The main types include AS, AP, SP and ASP. The mechanism of CCF is to make full use of different functions and synergy effect of various chemicals. Not only can it expand the macro swept volume by increasing the viscosity of the injection system, but also improve the micro displacement efficiency by reducing the interfacial tension between oil and water. Thus higher oil recovery can be gained. In China, fundamental research on CCF began in 1980’s. After more than 30 years’ indoor research and field tests, the technique has gone through four stages of development. At present, the mature technique is in the stage of industrialized application. Up to now, eight series of supporting techniques have been formed, 4 industrial tests of ASP combination flooding have improve oil recovery by 20%, and the ultimate recovery has been above 65%. Statistics show the cumulative oil production of all the CCF oilfield applications has exceeded 10 million tons. Remarkable development effect and economic benefit have been achieved. In China, CCF has become the dominant technique for greatly enhanced oil recovery after the used-to-be polymer flooding. At the same time, the field tests and application of CCF also exposed some problems and limitations, such as corrosion, scaling and output fluid emulsification caused by the existence of alkali, limited application in the relatively poor reservoirs with lower permeability, stronger heterogeneity, higher temperature and salinity. In the future, CCF technique will still face many challenges on its way of large scale applications in China. More emphasis will be put on the technical optimization and application’s expansion, namely from strong alkali-based ASP flooding to weak or no alkali-based ASP flooding, from high permeability reservoirs to reservoir with medium or low permeability reservoirs, from monolithic sandstone reservoirs to conglomerate or complex fault block reservoirs, from low temperature and low salinity reservoirs to high temperature and high salinity reservoirs. However, it is so exciting to see some new CCF techniques are booming now, such as alkali-free binary combination flooding and foam combination flooding etc. Some good expectations and results have been obtained in the laboratory research and pilot tests, showing broad application prospects and huge market potential.