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The Application of Microbial Geochemical Exploration Method in Lithologic Trap Exploration in Junggar Basin, China


3D seismic survey discovered multiple lithologic traps in the primary targeted layer of Jurassic Toutun river group on the eastern slope of Fukang depression in Junggar Basin. However, previous drilling results indicated that it is difficult to verify the oil and gas prospects of those traps due to the complex oil-water distribution in the research area, Microbial geochemical exploration technology is a sensitive and fast hydrocarbon detection method which is capable of indicating oil and gas distribution and properties by detecting microbial and sorbed soil gas anomalies in surface soil. In 2011, by applying MGCE survey in the research area, 3 hydrocarbon accumulation zones were identified, 6 oil and gas prospects were forecasted. The results revealed that microbial exploration findings matched well with previous drilling result and successfully forecasted the oil and gas potential of the 4 undergoing wells during the microbial survey. It is confirmed that MGCE is applicable as well as reliable in the exploration of lithologic reservoir on Fukang sag's eastern slope. In addition, by applying the “4G” comprehensive research method which combines Geology, geophysics, geochemistry and geobiology, a significant seismic anomaly was identified in Qigu formation vertically below the surface microbial anomaly. This formation has been neglected in the past for two reasons. (1) It is hard to justify its sealing conditions because the oil layer tapered out in updip direction onthe cretaceous unconformity surface. (2) No discovery has been made in this layer by previous drillings. Based on the 4G research results, well Fudong16 was drilled to the targeted anomaly located in Qigu group. On July 25th, 2012, Fudong 16 was tested by 3.5mm choke between well section 2022-2039m, and the natural flow of 17.25m3 oil per day was blew out from Qigu formation. This is a breakthrough discovery on Qigu lithologic reservoir in the whole region. The application of new technology provided new exploration model and opened up new exploration arena for explorationists. Key Words: Eastern slope of Fukang depression, Microbial geochemical exploration technology, Lithologic reservoir exploration, “4G” exploration research, Qigu group.