Study On Microbial Enhanced Waterflood Field Project At Yuejin Block In Qinghai Oilfield

The secondary recovery operation is mostly used in Qinghai Oil field, the formation water with high salinity and high calcium ion inhibits the chemical flood such as polymer flooding, surfactant waterflooding and active water flooding. In this paper, the microbes of water samples from five reservoirs had been investigated by both molecular biology method and most probable number method, and then the best activator and four bacteria strains had been selected, so we could determine the method of flooding.The experiment results showed that the category and number of microbes were more wealthy than others in the Youshashan and Huatugou reservoirs at 20-38℃. The permeability of Qigequan and Yuexi reservoir at 45℃is low less than 100μm~2, the microbes in the sample water were absent. The temperature of Gasi reservoir is 65℃, much higher than the other reservoirs, but the category and number of microbes were more than Qigequan reservoir, and less than Youshashan reservoir.Four bacteria strains were selected, One is Pseudomonsa Aeruginosa ZLD-1, which can metabolize biosurfactants; the second one named ZLD was able to live in the water at 15×10~4mg/L and emulsify crude oil at the salinity of 10×10~4mg/L; the third one named ZLG could disperse crude oil in the formation water at 65℃but could not grow at 38℃; The fouth one named ZLG-6 could disperse crude oil in the formation water at 65℃but could grow well at 38℃.The study results suggested that we can activate the indigenous bacteria in Youshashan and Huatugou reservoirs, and inject the suitable bacteria fermentation into different reservoirs.The research report could direct the microbe flooding method in Yuejin oil region, we have chose Gasi reservoir as an experiment field, the experiment is now running.