T20 The Unconventional Shale Systems: From Source-Rocks to Reservoirs I
Sunday, 22 September 2019
8:00 AM - 12:00 PM
Room 125AB, North Building
GEOCHEMICAL ANOMALIES OF THE LOWER SILURIAN SHALE GAS, SICHUAN BASIN, CHINA INSIGHT FROM THE RAYLEIGH-TYPE FRACTIONATION MODEL AND GEOLOGICAL DISTRIBUTION
Paper number: T20-5
Program: Technical Sessions
Time: 9:00 AM – 9:15 AM
Authors
Abstract
Unraveling the geological processes creating the geochemical anomalies of the shale gas in the Sichuan Basin has great significance for understanding the mechanism of gas generation in the late stage. Through the first supplement of gas samples in the southwestern part of the Fuling block and the expanded exploration areas in Changning-Zhaotong and Weiyuan, a systematic comparison study including gas composition, stable carbon, hydrogen and nitrogen isotopic composition, and noble gas component was carried out. The results reveal that the Lower Silurian shale gas is characterized by extraordinarily high methane (>96.11%) and low C2+ hydrocarbon (<0.51%).The δ15NN2 values of the LM shale gases range from −5.2 ‰ to −1.1‰, suggesting the nitrogen is produced from the thermal ammoniation of organic matter. Helium component is typical crustal genesis as its concentration range from 144.8 ppm to 237.5 ppm and its R/Ra range from 0.01 to 0.05. Full reversal (δ13C3< δ13C2< δ13C1) phenomenon and abnormally positive δ13C1 value constitute the carbon-isotope anomalies of the Lower Silurian shale gas.
References
Dai, J., C. Zou, D. Dong, Y. Ni, W. Wu, D. Gong, Y. Wang, S. Huang, J. Huang, C. Fang, D. Liu, 2016, Geochemical characteristics of marine and terrestrial shale gas in China: Marine and Petroleum Geology, v.76, p.44-463, doi: 10.1016/j.marpetgeo.2016.04.027.
Feng, Z., D. Liu, S. Huang, W. Wu, D. Dong, W. Peng, and W. Han, 2016, Carbon isotopic composition of shale gas in the Silurian Longmaxi Formation of the Changning area, Sichuan Basin: Petroleum Exploration and Development, v. 43, n. 5, p.769–777, doi: 10.1016/s1876-3804(16)30092-1.
Geological Society of America Abstracts with Programs. Vol. 51, No. 5
doi: 10.1130/abs/2019AM-340543
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