Effect of Methane Cracking on Carbon Isotope Reversal and the Production of Over-Mature Shale Gas

Jingkui Mi (), Wei Wu, Di Zhu and Ziqi Feng
Additional contact information
Jingkui Mi: State Key Laboratory for Enhanced Oil Recovery, Beijing 100083, China
Wei Wu: Exploration and Development Research Institute, PetroChina Southwest Oil and Gas Field Company, Chengdu 610041, China
Di Zhu: Key Laboratory for Biomass Gasification Technology of Shandong Province, Energy Research Institute, Jinan 250014, China
Ziqi Feng: School of Geosciences and Key Laboratory of Deep Oil and Gas, China University of Petroleum (Shandong), Qingdao 266580, China

Energies, 2022, vol. 15, issue 17, 1-12

Abstract: The geochemical statistics indicate that the wetness (C 2 ~C 5 /C 1 ~C 5 ) of over-mature shale gas with carbon isotope reversal is less than 1.8%. The magnitude of carbon isotope reversal (δ 13 C 1 –δ 13 C 2 ) increases with decreasing wetness within a wetness range of 0.9~1.8% and then decreases at wetness <0.9%. The experimental result demonstrates that CH 4 polymerization proceeding to CH 4 substantial cracking is an important factor involved in isotope reversal of over-mature shale gas. Moreover, δ 13 C 1 –δ 13 C 2 decreases with an increase in experimental temperature prior to CH 4 substantial cracking. The values of δ 13 C 1 and δ 13 C 2 tend to equalize during CH 4 substantial cracking. The δ 13 C 1 –δ 13 C 2 of mud gas investigated at different depths during shale gas drilling in the Sichuan Basin increases initially, then decreases with further increase in the depth, and finally tends to zero, with only a trace hydrocarbon gas being detectable. Thus, the approximately equal value between δ 13 C 1 and δ 13 C 2 for over-mature shale gas and very low wetness could potentially serve as useful criteria to screen CH 4 substantial cracking. Two geochemical indices to indicate CH 4 substantial cracking in a geological setting are proposed according to the variation production data with the geochemistry of over-mature shale gas in the Sichuan Basin, China.

Keywords: over-mature shale gas; magnitude of isotope reversal; CH 4 polymerization; CH 4 cracking; mud gas (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations:

Downloads: (external link)
https://www.mdpi.com/1996-1073/15/17/6285/pdf (application/pdf)
https://www.mdpi.com/1996-1073/15/17/6285/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:15:y:2022:i:17:p:6285-:d:900256

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().