Coupled Thermal-Hydrological-Mechanical-Chemical (THMC) Processes in Fractured Rocks in Deep Geothermal Energy Extraction

About the Project

This is a self-funded PhD position open to applicants worldwide, with a start date of either 1st October 2021 (preferred) or 1st October 2022. You will work with Dr Junlong Shang at the Geotechnics Group and the Energy and Sustainability Research Group at James Watt School of Engineering, University of Glasgow. This PhD project will focus on Coupled THMC modelling for renewable geothermal energy, with an ultimate goal to promote environmental sustainability.

Research Background

Actively seeking viable “clean/green” energy sources is important for human to maintain a sustainable development. Deep geothermal energy provides an important alternative to fossil fuels in our life. It is constant and would be available around the clock and in all sorts of weather, as it is supplied by the magma or decay of radioactive elements within the Earth. Most geothermal resources are deep-seated and are either deficient in fluid or permeability, or both (the so-called hot dry rock). Currently, the deep-seated, dry, and low-permeable geothermal reservoirs are often hydraulically fractured for permeability improvement, thereby promoting fluid circulations in engineered reservoirs and heat transportation to the ground. This is often referred to as enhanced geothermal systems (EGS). EGS has been a globally hot topic for renewable geothermal energy extraction. The development of EGS by hydraulic or chemical fracturing implies the consideration and understanding of coupled multiphysics (i.e., thermo-hydro-mechanical-chemical, THMC) mechanisms. Previous attempts in the understanding of THMC coupling behaviour ignored the impact of the ubiquitous natural incipient joints or crack-seal minerals on permeability evolution. As revealed by several major geothermal projects (e.g., the DEEPEGS Horizon 2020 project), veins are ubiquitously in upper crustal rock formations and deep geothermal reservoirs. Additionally, it is almost a ubiquitous feature that natural rock discontinuities in the underground are incipient, with considerable tensile strength and cohesion. The research questions of this project are 1) how does the coupled THMC behaviour control hydraulic fracture propagate in fractured rock cores containing veins or incipient rock joints? and 2) do the presence of incipient fractures can be the first-order control of the 3D geometry of hydraulic fractures? To address these questions, you will develop a coupled THMC model to for the first time look at how the 3D hydraulic fractures propagate within fractured media under geothermal reservoir conditions.

Research Method and Novelty

To investigate the key research questions outlined above, you will develop a THMC model by coupling the discontinuum method and an open-access multiphysics flow simulator (i.e., TOUGHREACT) to understand the coupled flow processes in fractured geothermal reservoir rocks. You will work closely with Glasgow Geoenergy Observatory and have the opportunity to get access to the X-ray CT scanner co-owned by the Universities of Glasgow and Strathclyde. You will also investigate the thermal response of crack-seal vein minerals. The outcome of the project can be used as a benchmark for geoscientists, engineers, and policymakers in further exploring and optimizing enhanced geothermal systems. The project is original because it will be for the first time research that considers the coupled flow processes in fractured and veined media under geothermal reservoir conditions. With the results from this study, you will provide timely and novel insights on the impact of the addition of natural mineral veins and incipient rock joints on the geometrical and mechanical properties of hydraulic fractures under geothermal reservoir conditions, assess and highlight its implications for reducing unwanted seismicity in the development of enhanced geothermal systems.

Entry requirements and online application

Applicants should hold first-class or upper second class degrees (undergraduate or an MSc degree) in an area of Civil Engineering, Geotechnical Engineering, Rock Mechanics, Geoscience, or other relevant areas. For applicants whose first language is not English, you will need to meet the minimum English requirement (IELTS 6.5, with no sub-bands less than 6.0, or equivalent).

You need to submit PhD application online https://www.gla.ac.uk/postgraduate/research/infrastructureenvironment/ and choose the programme PhD in Civil Engineering. You need the following documents during online application:

1. Transcripts/degree certificate

2. Two references

3. A one-page research proposal (can use the project information above)

4. CV

5. Name of potential Supervisor

For additional information, please contact Dr Junlong Shang.

Email: [Email Address Removed].

Research group website: https://shangjunlongcsu.wixsite.com/glasgow/openings

University staff website: https://www.gla.ac.uk/schools/engineering/staff/junlongshang/

Funding and Start Date

This is a self-funded PhD position open to applicants worldwide, with a start date of either 1^st October 2021 (preferred) or 1^st October 2022. I also welcome applicants who can bring funds from an outsider, such as the China Scholarship Council, Commonwealth Scholarships. Please specify this in your email when contacting me.

Reference

1. Shang, J., 2020. Rupture of veined granite in polyaxial compression: Insights from three-dimensional Discrete Element Method modelling. Journal of Geophysical Research: Solid Earth. Doi: https://doi.org/10.1029/2019JB019052
2. Shang, J., Hencher, S.R., West, L.J., 2016. Tensile strength of geological discontinuities including incipient bedding, rock joints and mineral veins. Rock Mechanics and Rock Engineering. 49(11): 4213-4225. Doi: https://link.springer.com/article/10.1007/s00603-016-1041-x
3. Shang, J., Jayasinghe, L.B., 2019 Three-dimensional DEM investigation of the fracture behaviour of thermally degraded rocks with consideration of material anisotropy. Theoretical and Applied Fracture Mechanics.Doi: https://doi.org/10.1016/j.tafmec.2019.102330
4. Duan, K., Kwok, C.Y., Zhang, Q.Y., Shang, J., 2020 On the initiation, propagation and reorientation of simultaneous multiple hydraulic fractures. Computers and Geotechnics. 117: 103226. Doi: https://doi.org/10.1016/j.compgeo.2019.103226
5. Rutqvist, J., Tsang, C.F., 2012. Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain. Reviews of Geophysics, 50, RG3006, 2012.
6. Westaway, R., Burnside, N.M., 2019. Fault ‘corrosion’ by fluid injection: potential cause of the November 2017 MW 5.5 Korean earthquake. Geofluids, 2019, 1280721, 23 pp., doi: 10.1155/2019/1280721