Geothermal

The subsurface provides a natural source of heat, that can be used both for direct use of heating or generation of electricity.

GEOTHERMAL

From district heating projects using shallow groundwater, to electricity generation using deep aquifers, geothermal resources are likely to be part of our future energy mix.

Leeds has the expertise to support the thorough investigation of the subsurface required for any geothermal project. Working with geothermal reservoirs is very similar to working with hydrocarbon reservoirs, and we can draw on several decades of research for the oil and gas sector to underpin our work in geothermal.

A viable reservoir for geothermal system will be a porous and permeable formation that allows extraction and injection of large volumes of water, bound by impermeable rock units that cap the geothermal reservoirs to prevent leakage. Whether the porosity and permeability are provided by the matrix itself (in sandstones, reef carbonates or over-pressured chalk) or through fractures (in tight sandstones and carbonates or crystalline rocks), our expertise in sedimentology and structural geology enables us to provide accurate reservoir characterisation.

Our engineering geologists are also looking at the geothermal potential in abandoned and flooded mine workings, where large volumes of water are retained at a stable temperature between 12-20°C. Our research covers the risks of instability caused by changes in water pressure and flow, as well as scaling and corrosion issues caused by geochemical changes.

Our strength in geophysics and basin analysis, incorporating sedimentology, structural geology, geothermal heat flow and geomechanics, can support the identification and optimisation of geothermal resources. This includes hydrothermal geochemistry to help understand the chemical properties of the geothermal waters; magmatic petrology to understand the nature of the heat source; structural geology using simulations to understand fluid flow behaviour in and around fault zones and fracture networks; and geomechanics to investigate permeability and rock stability in and around crystallizing magma bodies.

We also have the necessary expertise in tectonics to advise on the use and monitoring of seismicity, the small earthquakes caused by pressure changes in fluids underground, which are used to help fluids flow.

Recent research projects

Carbonate reservoir characterisation

The key aim of Carbonate Fault Rock Group is to create a step change in modelling the impact of faults on fluid flow in carbonate rocks. This has been achieved through a combined approach of new experimental work, data mining and integration of petrophysical and mechanical property analysis with microstructural analysis of fault rocks obtained from outcrop and core to identify the key geomechanical controls on fault rock properties, as well as their impact on fluid flow. The research helps predict geothermal reservoir performance in faulted carbonate rocks. Lead researcher: Prof Quentin Fisher.

Characterisation of flow regimes for shallow geothermal heat

This project focuses on understanding the flow zonation and the seasonal major ion geochemistry of the Northern Chalk Aquifer. The flow zonation is studied with open-well dilution testing, whereas the geochemistry is studied with loggers in springs and spring water sampling. Knowledge of ambient well flow velocities and flow patterns allow vertical hydraulic characterisation of depth intervals in wells, which are required for effective planning of future geochemical sampling, contaminant tracking, remediation activity, pumping test campaigns and shallow geothermal heat pump installation. Lead researcher: Dr Jared West, Rock Mechanics, Engineering Geology and Hydrogeology Group.

Characterisation of low permeability sandstone reservoirs

A key aim of Petrophysics of Tight Gas Sandstone Reservoirs (PETGAS) is to consolidate existing petrophysical data supplemented by new standard and special core analysis to create an atlas of the petrophysical properties of tight sandstones. This provides new insight into the controls of the petrophysical properties (e.g., diagenesis, grain-size, stress etc.), and stress dependency of permeability and relative permeability of tight sandstones. The research helps characterise tight sandstone reservoirs for gas, geothermal and CCS applications. Lead researcher: Prof Quentin Fisher.

REMIS - Reliable Earthquake Magnitudes for Induced Seismicity

Utilisation of subsurface resources for mining, carbon storage and hydrofracturing has the potential to induce earthquakes. Regulators use a “traffic light” system to manage this risk. However, existing methods used to characterise earthquakes do not account for the possible range of magnitudes, meaning that there will be cases where operations are incorrectly permitted to continue (or are halted) based on random variation or bias in the earthquake parameter estimates. The main objective of this project is to develop a new method to better image the Earth and enable the creating of specific, testable hypotheses of Earth processes and structure. This will lead to new recommendations to improve monitoring and high-value decision-making for the future of induced seismicity in the UK and worldwide and as a consequence our ability to utilise the subsurface for future decarbonisation. Lead researcher: Dr Andy Nowacki.

Stability analysis of shafts used for minewater heat recovery

Traditional heating using non-renewable energy resources contributes up to 50% of current carbon emission level. The water in abandoned mines provides an alternative source of thermal energy that can be extracted through newly drilled boreholes or existing mineshafts. Heat recovery through this mechanism may affect the structural stability of the mineshafts, therefore this project aims to ensure successful and sustainable operation through numerical sensitivity analyses on: (a) water level, (b) temperature fluctuations. Lead researcher: Dr Chrysothemis Paraskevopoulou, Rock Mechanics, Engineering Geology and Hydrogeology Group.

The evolution of natural geothermal systems

The magmatic-hydrothermal systems that form the economically-viable gold deposits are complex, and there remain significant gaps in understanding of how these systems evolve, particularly in the periods of, and between, ore genesis. This study aims to elucidate the physico-chemical conditions of the hydrothermal fluids that facilitate ore deposition in certain parts of an evolving magmatic-hydrothermal system. Understanding the evolution of such natural geothermal systems is crucial in predicting the sustainability of geothermal reservoirs. Lead researcher: Dr Dan Morgan, Leeds Ores and Mineralisation Group.

Geological characterisation of fluvial and aeolian sediments

The principal aim of the The Fluvial and Eolian Research Group is to conduct cutting-edge research into the application of fluvial and aeolian sedimentology for developing a better understanding of issues relating to environmental geology, hydrocarbon systems, mining and mineral exploration, appraisal of groundwater aquifers and carbon sequestration. This applied-facing research group seeks to devise new methodologies in subsurface geological characterization. The group operates as a Joint Industry Project. Lead researcher: Prof Nigel Mountney.

Geological characterisation of shallow marine sediments

The Shallow Marine Research Group focuses on cutting-edge applied shallow marine research, with emphasis on characterisation of subsurface sedimentary architecture to provide a better understanding of issues related to environmental geology, hydrocarbon systems, mining and mineral exploration, appraisal of groundwater aquifers and carbon sequestration. The research programme covers the following sedimentary environments and reservoir types: deltas, estuaries, paralic wave- and tide-dominated shorelines and clastic shelves. Lead researcher: Prof David Hodgson and Prof Nigel Mountney.

Impact case studies

Among the most promising, but least understood geothermal systems are those contained within carbonate rocks – namely limestones and dolostones. The way these rocks deform can fundamentally determine the viability of these geothermal reservoirs.
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Expertise at the University of Leeds is helping to de-risk exploitation of one of the main onshore sites with potential for UK deep geothermal: the Cheshire Basin.
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Satellite data reduces risk of geothermal plant operations
A satellite-based technique, originally used for monitoring volcanoes, is being utilised to help operators of geothermal energy plants better understand and manage the risks of earthquakes triggered by plant operation.