Chemical EOR (CEOR) technique is the dominant EOR technique in China. Recent progress of and remaining challenges in CEOR technologies in China is summarized in this paper. Key technical progress and field application results are also introduced.
As one of the mature chemical flooding technologies, polymer flooding has entered into industrialized applications stage in sandstone reservoirs. Polymer flooding has been applied in Daqing oilfield and 13% incremental oil recovery on average has been obtained over the past few decades. Polymer flooding has been also successfully applied to conglomerate reservoir in Xinjiang oilfield and complex fault block reservoir in Dagang oilfield. The most important CEOR technique is the alkali-surfactant-polymer (ASP) and surfactant-polymer (SP) flooding. The field tests showed that ASP flooding can significantly increase the oil recovery by 19-26% of OOIP. High efficiency and low cost surfactants for ASP formula were developed and ultralow interfacial tension was achieved. To avoid the negative effects of the alkali, five SP flooding field tests have been conducted in different reservoir types. The third CEOR technique is foam flooding. Many pilot tests have been performed, most projects obtained favorable recovery factor. The remaining challenges are how to develop more stable foam formula and inject the foam more effectively.
Polymer flooding is now expanding to complex reservoirs. ASP/SP flooding will be the leading EOR technology for high permeability reservoirs in China. The target reservoir is extended from sandstone reservoirs to complex fault block reservoirs and conglomerate reservoirs. Foam flooding is one of the potential CEOR technologies, especially in high temperature and high salinity reservoirs.