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Li H.,Northwest University, China | Ren Z.,Northwest University, China | Gao H.,Oil & Gas Exploration Company of Shaanxi Yanchang Petroleum Co. | Guo D.,Oil & Gas Exploration Company of Shaanxi Yanchang Petroleum Co. | And 4 more authors.
Natural Gas Industry | Year: 2015

The Yanchang Gasfield is located in the south central part of North Shaanxi Slope (the first-order structural unit), Ordos Basin. Although natural gas is abundant in this newly discovered area, there is little research related to the Upper Paleozoic source rocks. Consequently, progresses in exploration of the area are limited. Through comprehensive analyses of the organic matters, organic matter types, organic matter maturity and other properties, the distribution patterns, geochemical characteristics and hydrocarbon generation-expulsion properties of the Upper Palaeozoic source rocks were investigated. From the research, the following conclusions were made. (1) With organic carbon content of 60.18%-86.89% and total thicknesses of 6-18 m, coals are the major gas source rocks within the Upper Palaeozoic gas reservoirs, while mudstone is the second important gas supplier. Typically, mudstone in Shanxi Formation is classified as medium-high quality source rocks, while mudstone in Taiyuan and Benxi Formations serve as good-very good source rocks. (2) Kerogen in source rocks is dominated by humus type with Ro over 2.0%, which indicates a stage from over maturity to dry gas. (3) Source rocks in Upper Palaeozoic entered a massive hydrocarbon generation-expulsion stage in Middle-Late Jurassic-end of Early Cretaceous. Currently, hydrocarbon generation intensities vary at (25-65)×108 m3/km2 and expulsion intensities vary at (15-60)×108 m3/km2. In conclusion, coals have better hydrocarbon generation-expulsion capacities than mudstones. ©, 2015, Natural Gas Industry Journal Agency. All right reserved. Source

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