Abstract: To insight into the endogenous microbial communities and potential functions living in high pressure and high temperature (HPHT) reservoirs of Tarim Oilfield, crude oil pressure-volume-temperature (PVT) properties equipment was operated for deep wells in-situ sampling in both LN-A and TZ-B wells selected in Lunnan and Tazhong zone, respectively. Meanwhile, wellhead samples were collected as the control. The differences of microbial community diversity in oil-water samples were compared and analyzed. The metagenomics results showed that the dominant microorganism from in situ samples of LN-A well was Bacillus (56%), which of TZ-B well was Pseudomonas (50%). Comparing with samples from wellhead, the dominant microorganism was in accord with that of in-situ, however, the percentage was a little bit higher. The results of the two sampling methods showed that the microbial community structure was richer, dominant bacteria was dispersed, and more new functional microorganisms were found in deep well group (in-situ and wellhead samples were 14 and 3 species from LN-A well, respectively, while those of TZ-B well were 12 and 3 species). In this study, deep well in-situ collection, metagenomics and microbial community analysis technologies were integrated, which can help us fully understand and probe in-depth the functional microbial resource in HPHT reservoir. Additionally, this article can provide practical instructions and application value in microbial enhanced oil recovery technology performed in HPHT reservoir.

Key words: Tarim oilfield, deep well in-situ sampling, metagenomics, microbial diversity analysis, microbial enhanced oil recovery