Article Figures & Data
Figures
- Fig. 1.
Simplified overview of abandoned, flooded coal mines in the subsurface utilized for shallow, low-enthalpy mine water heat via abstraction and re-injection of groundwater, to heat homes and businesses. ©BGS, UKRI 2021.
- Fig. 2.
(a) Location of the Glasgow Observatory in the UK; (b) position of Observatory sites; (c) detail of Cuningar Loop mine water and environmental baseline characterization and monitoring boreholes. Ordnance Survey data ©Crown Copyright and database rights 2021. Ordnance Survey Licence No. 100021290 EUL.
- Fig. 3.
Simplified timeline of the definition and preliminary survey, exploration, appraisal (App.) and start of development (Dev.) stages of the mine water heat research infrastructure of the Glasgow Observatory.
- Fig. 4.
Cross-section through sites 1 and 3 of the Glasgow Observatory interpreted from new and legacy borehole data, mine abandonment plan records and using 3D geological models. ©BGS, UKRI 2021.
- Fig. 5.
Images of (a) drilling of the cored borehole GGC01 in 2018 and (b) installation of uPVC casing screen to mine water borehole with pre-glued gravel pack, electrical resistivity sensor cable (red sensors) and fibre optic cable. (a, b) BGS©UKRI 2020. (c) Research compound Site 1 at July 2020, background photograph courtesy BAM Nuttall.
- Fig. 6.
Labelled images of georeferenced scans of Farme Colliery mine abandonment plans in the vicinity of the Glasgow Observatory boreholes. Boreholes penetrating the coal seam or mine working are labelled. Plan scans © The Coal Authority 2021. All rights reserved. Borehole locations and labels by the authors. Borehole colours as in Figure 2c.
- Fig. 7.
Lithostratigraphical correlation panel of the Glasgow Observatory boreholes. Cuningar Loop boreholes summarized and interpreted from open hole rock chips. GGC01 sedimentology core log at a different scale. ©BGS, UKRI 2021.
- Fig. 8.
Interpretative 3D block diagram to illustrate borehole geometry, and proved and interpreted mine working variability indicated by abandonment plans. No vertical exaggeration (colours and fills as in Fig. 4). ©BGS, UKRI 2021.
- Fig. 9.
Rock chip log, caliper log and camera optical log images from the Glasgow Upper to Glasgow Main coal seam and mine workings section of boreholes GGA05 and GGA08. ©BGS, UKRI 2021.
- Fig. 10.
(a–h) Mine water reservoir classifications observed at the Glasgow Observatory with indications of their influence on hydraulic properties. ©BGS, UKRI 2021.
Tables
Site Borehole number Borehole type Drilling method: superficial and bedrock sections Total drilled depth from drill platform level (m) Drilled diameter at total depth Total casing depth from as-built datum (m) Screen depth from as-built datum (m) Screen type and internal casing diameter Description of screened interval ERT, fibre optics installed 1 GGA01 Mine water Superficial and bedrock: rotary, reverse circulation 52.00 406 mm (16 inches) 51.11 44.81–48.41 4 mm slotted with pre-glued gravel pack, 248 mm ID Overlying sandstone roof and Glasgow Upper mine working waste Y 1 GGA02 Sensor testing Superficial and bedrock: rotary, reverse circulation 94.16 406 mm (16 inches) 92.57 n.a. 248 mm ID n.a. Grout-filled Glasgow Main target interval, screen inside casing up to 67.2 m Y 1 GGA03r Environmental monitoring Superficial: rotary, direct circulation. Bedrock: rotary, reverse circulation 41.72 374 mm (14 ¾ inches) 40.81 37.00–39.81 3 mm slotted with pre-glued gravel pack, 146 mm ID Sandstone bedrock, above Glasgow Upper mine working N 2 GGA04 Mine water Superficial and bedrock: rotary, reverse circulation 53.63 406 mm (16 inches) 53.00 47.40–51.00 4 mm slotted with pre-glued gravel pack, 248 mm ID Overlying sandstone roof (fractured?) and Glasgow Upper mine working position, coal and mudstone Y 2 GGA05 Mine water Superficial: rotary, reverse and direct circulation. Bedrock: rotary, reverse circulation 88.50 406 mm (16 inches) 88.00 83.60–86.30 4 mm slotted no gravel pack, 248 mm ID Overlying sandstone roof and Glasgow Main mine working, void to mudstone floor Y 2 GGA06r Environmental monitoring Superficial: rotary, direct circulation 16.00 191 mm (7 ½ inches) 13.76 11.79–13.76 1 mm slotted with pre-glued gravel pack, 103.8 mm ID Sand and gravel in superficial deposits N 3 GGA07 Mine water Superficial: duplex drilling, direct circulation. Bedrock: rotary, reverse circulation 56.90 406 mm (16 inches) 56.61 50.91–53.61 4 mm slotted pre-glued gravel pack, 248 mm ID Overlying mudstone roof and Glasgow Upper mine working, coal pillar and void Y 3 GGA08 Mine water Superficial: rotary with reverse and direct circulation, and duplex drilling. Bedrock: rotary, reverse circulation 91.37 406 mm (16 inches) 87.95 85.08–87.70 4 mm slotted pre-glued gravel pack, 248 mm ID Overlying sandstone–siltstone and Glasgow Main mine roadway void Y 3 GGA09r Environmental monitoring Superficial: rotary, direct circulation 16.00 191 mm (7 ½ inches) 14.33 11.43–13.33 1 mm slotted with pre-glued gravel pack, 103.8 mm ID Sand in superficial deposits N 5 GGB04 Environmental monitoring Superficial: rotary, direct circulation 16.00 191 mm (7 ½ inches) 12.99 10.09–11.99 1 mm slotted with pre-glued gravel pack, 103.8 mm ID Sand and gravel in superficial deposits N 5 GGB05 Environmental monitoring Superficial: rotary with reverse and direct circulation, and duplex drilling. Bedrock: rotary, reverse circulation 46.00 374 mm (14 ¾ inches) 45.39 42.39–44.19 3 mm slotted with pre-glued gravel pack, 146 mm ID Sandstone bedrock, above Glasgow Upper mine working N 10 GGC01 Seismic monitoring Geobore S coring 199.00 151 mm 198.30 n.a. 76.6 mm ID n.a. N Grid references, drilled and datum heights are given in open data from ukgeos.ac.uk. n.a., not applicable; Y, yes; N, no. ©BGS, UKRI 2021.
- Table 2.
Features used to recognize mine workings during open hole rotary drilling of the Glasgow Observatory boreholes at Cuningar Loop in 2019; ©BGS, UKRI 2021
Feature Caused by: Recognized during Glasgow Observatory borehole drilling Clean drop of core barrel Open mine working, void GGA02, Glasgow Ell GGA05, Glasgow Main Increased rate of penetration, increased cuttings returns Easier progress though mine ‘waste’ (stowage or backfill, collapsed or fractured rock) GGA01, Glasgow Upper GGA02, Glasgow Upper GGA08, Glasgow Upper GGA08, Glasgow Ell Wobbling or ‘torquing-up’ of drill bit Sometimes indicates fractured rock mass GGA05 above Glasgow Main Smell of H2S (rotten eggs) and/or gas monitor alarm Mine gas or mine water Smell (alarm not activated): GGA01, Glasgow Upper GGA02, Glasgow Ell GGA05, Glasgow Ell (faint) GGA05, Glasgow Main GGA08, Glasgow Upper GGA08, Glasgow Main Loss of fluid flush If using direct circulation, fluid flush would be lost into the mine working Reverse circulation was used to avoid loss of flush Returns of iron- and sulphur-stained coal, mudstone, siltstone, sandstone (mixed lithologies) Returns of mine waste, may be loose to densely packed. Mixed, stained lithologies interpreted as stowage GGA01, Glasgow Upper GGA02, Glasgow Upper GGA08, Glasgow Ell GGA08, Glasgow Main Returns of wood, metal, rubber Roof support, pit prop, roadway, trackway and similar (first confirm nothing has been dropped down the borehole) GGA02, Glasgow Upper GGA08, Glasgow Main Returns of stained, altered coal Edge of coal pillar or collapsed, fractured pillar GGA07, Glasgow Upper GGA08, Glasgow Upper Excess water at shakers Fractured rock above mine working GGA08, above Glasgow Upper Substantial kick(s) in caliper log Void, waste or fractured rock GGA04, above Glasgow Upper GGA05, all 3 workings GGA07, Glasgow Upper GGA08, all 3 workings Voids, wastes, fractures, disturbed strata visible on optical camera GGA05, all 3 workings GGA07, Glasgow Upper GGA08, all 3 workings - Table 3.
Predicted and observed depth and lithology or type of the mine water boreholes, listed in order of drilling
Borehole; coal (in order of drilling) Predicted drill depth; Glasgow Upper and Main target workings with error margin (m) Observed drilled depths of mine working (top–base) from drill platform (m) Predicted mine working type from mine plans Observed mine working type Observed mining-related collapse and fracture features above or below working GGA02; GU 45 ± 4 47.80–48.95 Area of total extraction following earlier irregular-shaped worked areas and roadways Loose to moderately packed waste No data GGA02; GE 77 70.16–70.76 Total extraction Open void No data GGA02; GMA 83 ± 2 Not recognized Total extraction Not recognized; interpreted as cleanly collapsed working No data GGA01; GU 45 ± 4 47.60–48.86 Area of total extraction following earlier irregular-shaped worked areas and roadways Loosely packed waste; mixed lithologies No data GGA05; GU* 51 ± 2 49.46–51.00 Stoop and room (coal stoop or pillar) Coal pillar Horizontal bedding planes for c. 6 m above appear as open fractures. About 0.2 m disruption below pillar in claystone floor (caliper kick). Minor loss during annulus grouting. Fracture for c. 2 m beneath floor lift or heave or pillar punching? GGA05; GE* 72† 71.90–72.6 Total extraction Tightly packed waste c.0.7 m, not recognized during drilling, seen on optical camera and caliper log Fractures 1–2 m above and below the mine working from optical camera GGA05; GMA* 86 ± 2 84.66–85.36 Total extraction Open, water-filled void. Underlying floor lift zone Disrupted floor zone on optical camera and caliper data. Siltstone–fine sandstone rock chip returns (not waste), interpreted as 1.7 m of floor lift GGA04; GU 51 ± 2 49.46–50.60 Stoop and room (room or void) Fractured roof and coal; edge or collapsed pillar? Caliper log and rock chip returns indicate c. 1.5 m fractured sandstone in roof of coal. Also caliper kick in mudstone below coal GGA08; GU* 51 ± 2 52.50–53.70 Total extraction Intact coal and waste; hit edge of a pillar Optical camera and caliper show disrupted mudstone roof c. 1 m above. Disrupted floor c. 0.2 m below GGA08; GE* Between 72 and 81† 74.70–76.50 Total extraction Densely packed waste Optical camera and caliper show fracture and migrated void 2 m above mine working. Intact rock below GGA08; GMA* 88 ± 2 87.70–90.70 Total extraction and former roadway Open void to collapsed material, wood, waste; the thickness indicates a mine roadway Fractures for around 1.2 m above roof of mine working on optical camera GGA07; GU* 51 ± 2 52.2–53.9 Total extraction Coal pillar and void on optical camera and caliper kick Fracturing not discernible in mudstone roof *Optical camera data are available and constrain the interpretation. GGA04 interpretation includes open hole caliper data but not optical camera data.
†Adjusted from published pre-drill predictions during the drilling phase based on the depth of GGA02.
GU, Glasgow Upper; GE, Glasgow Ell; GMA, Glasgow Main. ©BGS, UKRI 2021.
Drilling into mines for heat: geological synthesis of the UK Geoenergy Observatory in Glasgow and implications for mine water heat resources
- Article
- Abstract
- Description of the Glasgow Observatory
- Pre-drill geological and mining legacy datasets
- Results: borehole drilling and construction
- Results: post-drill lithology and stratigraphy
- Results: post-drill mine workings
- Discussion
- Conclusions
- Acknowledgements
- Author contributions
- Funding
- Data availability
- References
- Figures & Data
- Info & Metrics