University of Cambridge- PhD Studentship

Degassing of a CO₂ system: U-Series constraints on the evolution of the Green River (Utah) natural analogue for geological carbon storage

Supervisor: Mike Bickle, Albert Galy (Earth Sciences, Cambridge) & Dan Condon (British Geological Survey)

Applications are invited for a PhD project fully funded by the British Geological Survey and the Department of Earth Sciences, University of Cambridge.

This PhD project is focussed on using U-Series dating, combined with other geochemistry (e.g. Sr/Ca, δ¹³C, ⁸⁷Sr/⁸⁶Sr) and numerical modelling to understand the tempo of CO₂ degassing in a natural CO₂ leaking system, a natural analogue for potential future storage systems. The student research experience will build upon existing synergy between groups at Cambridge and the BGS and will generate data that are pertinent to our understanding of CO₂ storage on time scales of 1 to >100 kyr, detailing rates and nature of fundamental processes/reactions, and the response of CO₂ reservoirs to external forcing (i.e., environmental change).

A key aspect of geological carbon storage is the need to ensure that the storage is safe and efficient and this requires the ability to model the fate of the CO₂ over the ~ 10,000 year storage period. The only direct observations of CO₂ systems on such timescales are on sites of natural CO₂ storage and this project will study the CO₂ system at Green River, Utah, where CO₂ has been leaking for over a 100 ka.

The CO₂ at Green River leaks along faults to surface at a series of natural and anthropogenic geysers which form complex veined travertine deposits. These have been dated by U-series methods and the results show that degassing of the CO2 has been most intense when the crust unloads during deglaciation events. Trace element ratios (e.g. Sr/Ca) and isotopic compositions (δ¹⁸O, δ¹³C, ⁸⁷Sr/⁸⁶Sr) of the carbonate veins constrain the magnitude and mechanisms of the CO₂ degassing. Geochemical, isotopic and U-series analyses will be used to map and model the history of CO₂ degassing and understand the mechanisms by which CO₂ penetrates fault systems in a complex stratigraphy. The results on surface samples will be compared to analyses of samples from drill core through the current CO₂-charged aquifer to evaluate the magnitude and rates of carbonate mineral precipitation. The project will take advantage of core drilled by Shell in 2012 through the main CO₂ reservoir at Green River and planned drilling of fault zones for 2013.

The student will map and sample travertines at the Green River site and carry out a series of geochemical and isotopic measurements to understand the timing and mechanisms of CO₂ degassing. U-series analyses, carried out at the NERC Isotope Geochronology laboratories, will provide a high resolution chronology. Initial analyses show that it is possible to date the growth of individual carbonate veins over periods of a few thousand years.

The student will be trained in field mapping and sampling for the geochemical and isotopic analyses. They will learn a wide range of geochemical and isotopic analytical techniques and how to use these to model the geological processes involved in CO₂ degassing. The student will become familiar with the processes and requirements for geological carbon storage. They will join a group of more than 10 (faculty, post-docs and students) working on a whole range of problems related to CO₂ storage. The student will be encouraged to interact with this group who are researching aspects of geological carbon storage including modelling of multi-phase flow, seismic imaging of reservoirs and studying cap-rock integrity and the fluid-fluid and fluid-mineral reactions within reservoirs.

Publications:
Bickle, M.J., Geological carbon storage. Nature Geoscience 2 (12), 815-818 (2009).

Kampman, N., Bickle, M., Becker, J., Assayag, N., and Chapman, H., 2009, Feldspar dissolution kinetics and Gibbs free energy dependence in a CO₂-enriched groundwater system, Green River, Utah: Earth and Planetary Science Letters, v. 284, p. 473-488.

Kampman, N., Burnside, N. M., Shipton, Z. K., Chapman, H. J., Nicholl, J. A., Ellam, R. M., and Bickle, M. J., 2012, Pulses of carbon dioxide emissions from intracrustal faults following climatic warming: Nature Geoscience, v. 5, p. 352-358.

Wigley, M., Bickle, M., Kampman, N., and Dubacq, B., 2012, Fluid-Mineral Reactions in an Ancient CO₂ Reservoir, Green River, Utah.: Geology, v. 40, p. 555-558.

To apply contact Mike Bickle (JavaScript must be turned on for you to be able to see this address) or Albert Galy (JavaScript must be turned on for you to be able to see this address) in the first instance sending a CV and names of referees.