The properties of petroleum inclusions and stages of hydrocarbon accumulation in Mesozoic-Cenozoic reservoirs in Yingmaili area of Tabei uplift, Tarim Basin

To clarify the stages and evolution process of hydrocarbon accumulation is presently the key issue of exploring Mesozoic-Cenozoic reservoirs in Yingmaili area of Tabei uplift, Tarim Basin. A detailed study was carried out to determine the properties of petroleum inclusions and the stages of hydrocarbon accumulation in Mesozoic-Cenozoic reservoirs using rock samples from typical wells, through a combination of microscopic examination, micro-beam fluorescence spectroscopy, and micro-thermometric technique. Results showed that petroleum inclusions in reservoirs rocks mainly emitted blue, blue-white, bright yellow, and weak yellow fluorescence. Peak wavelengths of the fluorescence spectra were mainly distributed in the ranges of 470-490 nm and 510-540 nm, corresponding to blue-white and yellow fluorescence, respectively. Of these, petroleum inclusions emitting yellow fluorescence had the red-green quotient of 0.48-0.65 and the chromaticity of 0.345-0.360 (CIE-X) and 0.358-0.375 (CIE-Y), whereas the corresponding brine inclusions had the main peak of homogeneous temperatures at 80-90℃. Differently, petroleum inclusions emitting blue-white fluorescence had the red-green quotient of 0.20-0.51, CIE-X of 0.302-0.333, and CIE-Y of 0.325-0.352, whereas the corresponding brine inclusions had the main peak of homogeneous temperatures at 120-130℃. Combined with simulation analysis of burial history and thermal evolution history, two-stage hydrocarbon accumulation was identified in Mesozoic-Cenozoic reservoirs in Yingmaili area: in the first stage (8-5 Ma), mainly normal reservoirs were formed with relatively low maturity and petroleum inclusions emitting yellow fluorescence; and in the second stage (since 3 Ma), mainly condensate reservoirs were formed with relatively high maturity and petroleum inclusions emitting blue-white fluorescence. ©, 2015, Science Press. All right reserved.