Abstract
In order to establish sustainable heat loading (heat removal and storage) in abandoned flooded mine workings it is important to understand the geomechanical impact of the cyclical heat loading caused by fluid injection and extraction. This is particularly important where significantly more thermal loading is planned than naturally occurs. A simple calculation shows that the sustainable geothermal heat flux from abandoned coal mines can provide less than a tenth of Scotland's annual domestic heating demand. Any heat removal greater than the natural heat flux will lead to heat mining unless heat storage options are also considered. Thematic collection: This article is part of the SJG Collection on Early-Career Research available at: https://www.lyellcollection.org/cc/SJG-early-career-research
Highlights
As a first step, a steady-state, fully saturated, 2D coupled hydromechanical model of a generalized section of pillar-and-stall workings has been created
The modelled uplift to water-level rise ratio of 1.4 mm m−1 is of the same order of magnitude (1 mm m−1) as that observed through interferometric synthetic aperture radar (InSAR) data in the coalfield due to mine water rebound
Mine heat systems are expected to cause smaller changes in pressure than those modelled but the results provide initial implications on the potential geomechanical impacts of mine water heat schemes which abstract or inject water and heat into pillar-and-stall coal mine workings
Summary
A steady-state, fully saturated, 2D coupled hydromechanical model of a generalized section of pillar-and-stall workings has been created. Mine water rebound was modelled by increasing the hydrostatic pressure sequentially, in line with monitored mine water-level data from Midlothian, Scotland. Mine heat systems are expected to cause smaller changes in pressure than those modelled but the results provide initial implications on the potential geomechanical impacts of mine water heat schemes which abstract or inject water and heat into pillar-and-stall coal mine workings. The utilization of abandoned flooded mine workings in the UK could provide a renewable heat source near to centres of population. It has been estimated that a third of Scotland’s heating requirement could be obtained by utilizing shallow abandoned coal mine workings (Gillespie et al 2013) this may be considered ‘heat mining’, i.e. abstracting more than is sustainable. One of two new UK Geoenergy Observatories is located in Glasgow to research the mine water environment in the context of developing mine water heat technology (Monaghan et al 2018)
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