A review of alkane gas geochemistry in the Xujiaweizi fault-depression, Songliao Basin.pdf

Marine and Petroleum Geology 43 (2013) 284e296
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Marine and Petroleum Geology
journal homepage: ate/marpetgeo
A review of alkane gas geochemistry in the Xujiaweizi
fault-depression, Songliao Basin
Huasen Zeng*, Jingkun Li, Qiuli Huo
Exploration and Development Research Institute, PetroChina Daqing pany, Daqing, Heilongjiang 163712, China
article info abstract
Article history: A large suite (172) of gases from the Yingcheng Fm. in the Xujiaweizi fault-depression has been studied
Received 6 March 2012 chemically and isotopically. The results show that they are mainly type-III kerogen/coal-type gas and
Received in revised form have been generated and accumulated under the influence of hydrothermal fluids. Both measured
22 January 2013
and calculated vitrinite reflectance data show that they have been generated mainly at source
Accepted 24 January 2013 13 13
maturity higher than %Ro. Many gases show carbon isotopic reversals (typically, d C1 > d C2 and
Available online 31 January 2013 13 13
d C2 > d C3). The origin of carbon isotopic reversals is discussed in this paper and the results show that
previous interpretations, including (a) mixing and (b) the occurrence of abiogenic gases, are incorrect.
Keywords:
Songliao Basin Based on iso-butane/n-butane data, wet-gas cracking may have occurred but it is not the main cause of
Volcanic reservoir carbon isotopic reversals here. We propose that a process of abiogenic polymerization of C2þ gases with
Carbon isotopic reversal methane is the main cause of the carbon isotopic reversals in this basin.
Wet-gas cracking Ó 2013 Elsevier Ltd. All rights reserved.
Abiogenic polymerization
1. Introduction >%Ro (. over-mature) have received much less attention to
date. However, recently published gas data with source maturity
The carbon isotopic and positions of natural gas >% all show carbon isotopic reversal phenomena (typically,
13 13
have