Spotlight on a Student: PhD Candidate Meghalim Phukan

Mineral precipitation from C02-saturated water in basalts and its potential for self-sealing of fractures and joints

Meghalim_Phukan

What is your research about?

My research is about geological carbon storage which permanently disposes carbon dioxide into the subsurface to reduce global warming. Sedimentary basins have been studied for a relatively long time and are in principle considered as a conventional storage reservoir for CO2. In this case, mineralisation of CO2might take thousands of years to occur as sedimentary rocks are not so reactive. But in recent years, continental flood basalts are considered as unconventional CO2storage reservoirs where interbedded impermeable massive basalt zones serve as barriers for upward CO2migration. However, vertical joints and subvertical fractures may serve as conduits for buoyancy-driven CO2migration and compromise the effectiveness of CO2containment. Basalts contain glass and silicate minerals with high Ca, Mg and Fe concentrations, which dissolve when exposed to CO2-enriched, low-pH water. The dissolution of basaltic minerals and glass consumes protons resulting in an increase in pH and leads to an enrichment in dissolved ions to the point when secondary minerals precipitate. Mineral precipitation in joints and fractures may be sufficient to partly or fully block fluid flow.

The objective of my PhD research is to understand the nature and extent of mineral precipitation under CO- saturated conditions leading to self-sealing of fractures in basalts. My project involves sourcing and characterizing the basalt sample, like its chemical and mineral composition, rock porosity and permeability. Sample characterization was followed by high pressure and temperature batch reactor experiments on massive basalt wafers under CO2saturated condition. I also work on geochemical models to understand whether certain minerals are under or supersaturated at certain times during the experiment.Secondary mineral phases have been observed in the basalt wafers and its mineralogy matches closely with the geochemical modelling results.These secondary minerals could be potential sealants and mitigate CO2leakage.In order to determine the self-sealing capacity of fractures under same CO2storage conditions, another batch experiment was carried out focusing on the change in fracture dimension on an artificial fractured massive basalt core and the results are still underway.

About 10% of the Earth surface is covered with basalt and carbon storage in basalt could become one of important solution (besides the use of renewable technologies) for greenhouse gas mitigation in near future.

Who are your supervisors?

I have a very supportive team of supervisors within the Earth Science Department at the University of Melbourne. My principal supervisor is Prof Ralf R. Haese, who is also the current Director of the Peter Cook Centre for CCS Research. Dr Hong Phuc Vu, who is an experimental geochemist and a modeler has worked at the University for the last 7 years on various projects and serves as my honorary supervisor.

What do you want to do next?

I enjoy designing and conducting geochemical experiments. Currently, I am in my final year and focussing on finishing my Ph.D., but later I would like to keep my options open for an industrial job or in academics.

Any awards

My research is funded by Melbourne Research Scholarship, and I am very grateful to receive travel grants from the Bharagwanath Geology Research Scholarship in 2017 and 2018. I attended the McDonnell 7thInternational Symposium focussed on the topic “Global Challenges for Today’s Research Universities: Health, Energy and Environment, and Agriculture” in Beijing, China. The travel grants will also support my upcoming Gordon Research Conference on “Carbon Capture, Utilization and Storage” in May 2019 at Les Diablerets, Switzerland.

Meghalim and her supervisors welcome any enquiries about her research. You can email her at mphukan@student.unimelb.edu.au

More Information

Ruby Brown

ruby.brown@unimelb.edu.au

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