Abstract
The geochemical characteristics of natural gases from Lower Paleozoic Jingbian gas field are abnormal and the carbon isotope of most natural gases has reversed, which led to a dispute over the source of natural gas in the Lower Paleozoic. The Upper Paleozoic Yulin gas field is adjacent to the Jingbian gas field, but the geochemical characteristics of the Yulin gas field did not appear abnormal. Besides, the ethane carbon isotope of Upper Paleozoic Yulin gas field is much higher than that of Lower Paleozoic Jingbian gas field. In order to identify the reasons for the carbon isotope reversal of natural gas in Lower Paleozoic Jingbian gas field and its relationship with natural gas source, We conducted the components and stable carbon isotopes of natural gas from Upper Paleozoic Yulin gas field and Lower Paleozoic Jingbian gas field. On the basis of these experiments, we compared the natural gas components and carbon isotope of 100 samples from both Upper Paleozoic Yulin gas field and Lower Paleozoic Jingbian gas field. The results indicate that higher maturity will break the conventional rule, when maturity reaches a certain threshold; δ13Cethane value will decrease with maturity. Although δ13Cmethane value will also increase with maturity, the extent will be relatively smaller. This leads to unusual δ13Cmethane > δ13Cethane in the region with higher maturity. In the process of downward migration of coal-derived gas from Carboniferous-Permian coal measures, component fractionation and carbon isotope fractionation might occur, resulting the ethane components and carbon isotope value of Lower Paleozoic less than those of Upper Paleozoic, which will lead to the carbon isotope reversal. The mixing of oil-derived gas and coal-derived gas at different ratios may also lead to the reversal of carbon isotopes. The natural gas types of Jingbian gas field are mainly coal-derived gas generated from Carboniferous-Permian coal measure strata, with a small amount of oil-derived gas generated from Carboniferous-Permian marine-terrigenous limestone.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
