2023 Fiscal Year Research-status Report
Application of methane clumped isotope approach in natural abiotic methane reservoirs
| Project/Area Number |
22K14134
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
張 乃忠 東京工業大学, 理学院, 東工大特別研究員 (90782772)
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | Biodegradation / Abiotic methane / Mud volcano / Clumped isotope / Isotope |
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| Outline of Annual Research Achievements |
During past years, we have established a novel method, named as methane clumped isotope analysis, at Tokyo Institute of Technology, for tracking the formation and consumption mechanisms/sources of methane. This study is the extension from our lab methane synthesis experiment to understand the methane behavior in nature. We have sampled methane and other hydrocarbons from different natural reservoirs, including both mud volcanos and surface gas seeps around the oil and gas field, e.g. (1) Tokamachi area (Gamo, Murono and Kusozu), and (2) Goshogake area.
According to the methane clumped isotope analysis, as well as other geochemical approaches applied in carbon species, we have successfully constrained the contribution of microbial activity in Tokamachi mud volcanos, which provide direct evidence of secondary microbial methane production during biodegradation process.
Our study in Goshogake area is still ongoing, and the preliminary carbon and hydrogen isotope results suggest CH4 may be derived from a mixture of abiotic and thermogenic sources. Due to the extremely low concentration of CH4 (0.1-0.2%), we will try to analyze the clumped isotope signatures by establishing a preconcentration and purification system.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
We have finished the analysis in Tokamachi mud volcanos and are working on the finalization of the manuscript to report our observations, which is expected to be submitted in coming months.
For Goshogake mud volcanos, we have analyzed the gas compositions, carbon and hydrogen isotopes of carbon species, nitrogen isotopes in N2 and sulfur isotope in H2S. Nobel gas isotope analysis is ongoing. Due to the low concentration of CH4, we are now working on establishing a preconcentration and purification system to obtain enough methane for clumped isotope analysis.
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| Strategy for Future Research Activity |
The future work will focus on the gas analysis of samples collected from Goshogake mud volcanos. We will develop the CH4 preconcentration and purification system to obtain 3-4 mL pure CH4 from 3-5 L gas samples (0.1-0.2%) collected from Goshogake. Nobel gas isotopes and CH4 clumped isotope will be analyzed for better clarifying the source of hydrocarbons in such environment, as well as the geological and geochemical settings of Goshogake system.
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| Causes of Carryover |
Due to the low concentration of methane in Goshogake samples, we have to develop a preconcentration system to prepare samples, which require longer time than expected. So we need keep some money which can be used for methane clumped analysis.
Therefore, the residue of funds will be used for purchasing consumables of CH4 clumped isotope analysis in the new fiscal year.
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