Subsurface Voids – Implications for Shallow Coal Mine Geothermal

Coal extraction (Durham and Northumberland Coal Fields) has largely taken place using the pillar and stall method. For mine geothermal prospects, the majority of flow will occur through open stalls, which will have very high permeabilities and porosities. However, pillars and temporary supports that were designed to sustain the weight of overburden can over time fail resulting in mine roofs to collapse. Furthermore, the occurrence of goaf (backfilled mine waste), caving’s, localised dissolution and lithological heterogeneity of the Carboniferous coal measures are important to appraise as they will significantly affect the capacity and flow properties within mine workings. This research has investigated former coal mine anthropogenic deposits along the Northumberland coast at Whitley Bay and integrated with borehole and core data sets from the local region. The project has undertaken extensive detailed fieldwork with sedimentological field data collection focusing stratigraphically on the Upper Carboniferous (Westphalian) High Main coal seam. Detailed permeabilities, porosities and petrography were collected from different lithologies in the field. The research demonstrates how any collapse, spalling of the roof and backfilled roadways will have very low permeabilities (~0.01mD to 0.001mD) but low to moderate porosities (~3-8%) compared to the surrounding lithologies and may act as long-term barriers to flow. Closely associated and laterally connected sandstones and siltstones frequently have much higher permeabilties (~100-300mD) and porosities (~15-25%). Older mine workings that have experienced greater degrees of compaction and anthropogenic heterogeneity may be less viable as geothermal reservoirs. The findings presented establish one of the first data sets that can be used for modelling of geothermal prospects in former coal mine workings and aims to establish anthropogenic sediment characteristics to help de-risk potential subsurface mine workings.

Stuart Jones is a sedimentologist that specializes in subsurface reservoir characterization using the joint application of subsurface and outcrop sedimentological data for improved model development and reducing subsurface risk and uncertainty. This research is particularly important for the energy transition and characterization of the subsurface geology for CCS, hydrogen storage and geothermal. Stuart’s academic roots in sedimentology were firmly established after completing a BSc in geology at University of Aberystwyth, and a PhD in alluvial sedimentation of the Spanish Pyrenees at the University of Reading, he then joined the hydrocarbon industry before returning to academia with a Royal Society Postdoctoral fellowship at the University of Southampton. In Late 2002, he joined Durham University where he has continued to develop his multidisciplinary international research and since supervised well over >50 PhD students. In 2018 he received the Durham University Excellence in Doctoral Supervision award (nominated by his postgraduates).

Stuart has extensive experience of delivering large, long-term research programmes and collaborating with industry. He is is leader of the international GeoPOP research consortium (>£4M), a multi-disciplinary research group investigating overpressure in sedimentary basins and funded by the Energy sector (www.geopop.org.uk) with phase 5 due to start mid-2025. Understanding geopressure is critical for safe Carbon dioxide, hydrogen and compressed air storage in the subsurface. Recent funding success of £2.1M from Industry (ENI, UK) will be led by Stuart and focus on the HyNet innovative low carbon and hydrogen energy project that will unlock a low carbon economy for the NorthWest and North Wales. Geothermal Energy from Mines and Solar Geothermal Heat (GEMS) is a Durham Energy Institute (DEI) interdisciplinary project funded by UKRI (£1.8M) and is a leading group investigating the potential of geothermal energy in the UK. The successful research programmes ran by Stuart has allowed further support with a recent successful Capital Equipment Grant (£750k) for a state-of-the-art automated quantitative mineralogy laboratory (SEMs) and supported by Zeiss microsystems.

Stuart has been widely recognized for his innovative and high-quality teaching of Earth Sciences by Durham University and nationally through STEM Learning and the UK Prime Minister award. Stuart is an active champion of Earth science outreach and importance of NetZero Energy transition regularly undertaking CPD for teachers, public engagement and founder of award-winning Earth Science into Schools module that is now a cross-faculty module. Currently, he is chair of the North Pennines GeoPark Advisory Board, a Member of the Geological Society of London Education Committee as well as science advisor for several NE Primary and Secondary science SCITT’s.

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18:50 to 19:00 - Q & A

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