Abstract: Based on the lab experiments and field tests of in-situ original microbes drive in light oil blocks and the lab feasibility studies of such a drive in heavy oil blocks in Karamay oilfield, the features and applied values of the protist in light and heavy oil reservoirs in this oilfield are presented. It is suggested that in light oil blocks the content of in-situ original microbes is relatively low, with poor activity, for this reason, the screening, culturing and re-injection of the microbes can notably enhance the oil recovery (EOR) of these reservoirs, while in heavy oil blocks the content of in-situ original microbes is relatively high, with good activity, using direct injection of culture medium to activate such microbes is more ideal for EOR, at the same time, the viscosity-reducing process by emulsification for high-viscosity and high-calcium heavy oil can be realized, with viscosity-reducing rate of over 50% and de-calcium rate of over 90%.

Key words: Karamay oilfield, light oil, heavy oil, protist, in-situ original microbe, EOR