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Understanding methane history and reservoir potential in the South China Sea


   Department of Earth and Environmental Sciences

  ,  Applications accepted all year round  Self-Funded PhD Students Only

About the Project

Sustainable hydrocarbon gas extraction is necessary as a key part of the energy transition away from the most polluting hydrocarbon energy sources. The Qiongdongnan Basin is a Cenozoic sedimentary basin in the northern continental shelf of the South China Sea which is a promising candidate for further natural gas extraction. It is a basin that has experienced high heat flow and high geothermal gradients due to rapid tectonic subsidence in the last 5Myrs. Overpressure due to associated tectonic compression and hydrocarbon generation can result in a fractured network for hydrocarbon migration, where free gas can accumulate in litho-stratigraphic traps. Understanding the connectivity of fluids within a hydrocarbon reservoir is critical to efficient hydrocarbon extraction. Although there are drill test techniques to assess well storage capacity and permeability, and compositional differences in bulk chemistry can indicate mixtures of hydrocarbons with varying maturity, an inert tracer is needed to assess the extent of lateral and vertical connectivity on a basin scale, with particular focus on lateral connectivity of the major oil/gas bearing sags that are present across the Qiongdongnan Basin.   

The inert nature of noble gases makes them ideal tracers of fluid flow and mixing as they do not chemically react with hydrocarbons (although there can be physical processes of adsorption / desorption and diffusion). Noble gases are also useful because they partition in a predictable way between a gas phase and different fluid phases (oil and water). In addition, radiogenic noble gases can accumulate to provide chronological information. Noble gas data will be supplemented by clumped isotope methane data, which will provide unambiguous information about the formation temperatures of methane and therefore where methane formed and how it has subsequently migrated. Bulk gas chemistry particularly, CO2 content, will also be critical for understanding reservoir connectivity and gas origins across the Basin.

This project aims to investigate methane gas origin, and reservoir connectivity and fluid interactions after gas formation to establish the potential of Qiongdongan Basin for further sustainable hydrocarbon gas extraction.

Samples comprise ~50 gas canisters taken directly from offshore drilling platforms. Samples will be characterised using standard gas chromatography techniques to provide bulk chemistry of gas samples. Noble gas isotopes of all noble gases will be analysed using noble gas mass spectrometry. Methane clumped isotopes will be analysed using quantum cascade laser spectroscopy systems. Standard gas chromatography techniques will be used to provide bulk chemistry of gas samples.

Suggested skills needed: The project would suit a student interested in reservoir basin origin and evolution and geochemistry. This is a laboratory-focussed project so good practical skills and a willingness to learn and apply analytical techniques is essential. A background in geoscience, physics or chemistry at undergraduate level is desirable.

Please contact Greg Holland () if you are interested and wish to find out further information.

Your application must be made online at https://www.ees.manchester.ac.uk/study/postgraduate-research/how-to-apply/ .Please search and select PhD Earth Science (academic programme) and PhD Earth Science (academic plan)


Funding Notes

This is a self funded project.
22/23 fees for Home students are £16,500 and for EU and International £37,500.

References

Su et al (2018) Petroleum Science and technology, 36, NO. 24, 2125–2131 https://doi.org/10.1080/10916466.201
Fan et al. Geosci. Lett. (2018) 5:13 https://doi.org/10.1186/s40562-018-0112-0
Cao, C. et al (2020) Journal of Natural Gas Science and Engineering. 78, 103304. DOI: 10.1016/j.jngse.2020.103304
Goncheng, Z. et al (2014) Natural Gas B1 41-50.

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