Ranking the geothermal potential of radiothermal granites in Scotland: are any others as hot as the Cairngorms?

Prior investigations concur that the granite plutons in Scotland which are most likely to prove favourable for geothermal exploration are the Ballater, Bennachie, Cairngorm and Mount Battock plutons, all of which have heat production values greater than 5 μW m−3. This heat production arises from the significant concentrations of potassium, uranium and thorium in some granite plutons. A new field-based gamma-ray spectrometric survey targeted plutons that were poorly surveyed in the past or near areas of high heat demand. This survey identifies several other plutons (Ben Rhinnes, Cheviot, Hill of Fare, Lochnagar and Monadhliath) with heat production rates between 3 and 5 μW m−3 that could well have geothermal gradients sufficient for direct heat use rather than higher temperatures required for electricity generation. The Criffel and Cheviot plutons are examples of Scottish granites that have concentric compositional zonation and some zones have significantly higher (up to 20%) heat production rates than others in the same plutons. However, the relatively small surface areas of individual high heat-production zones mean that it is unlikely to be worthwhile specifically targeting them

Gamma-ray spectrometry in the field: Radioactive heat production in the Central Slovakian Volcanic Zone

We report 62 sets of measurements from central-southern Slovakia, obtained using a modern portable gamma-ray spectrometer, which reveal the radioactive heat production in intrusive and extrusive igneous rocks of the Late Cenozoic Central Slovakian Volcanic Zone. Sites in granodiorite of the Štiavnica pluton are thus shown to have heat production in the range ~ 2.2–4.9 μW m− 3, this variability being primarily a reflection of variations in content of the trace element uranium. Sites in dioritic parts of this pluton have a lower, but overlapping, range of values, ~ 2.1–4.4 μW m− 3. Sites that have been interpreted in adjoining minor dioritic intrusions of similar age have heat production in the range ~ 1.4–3.3 μW m− 3. The main Štiavnica pluton has zoned composition, with potassium and uranium content and radioactive heat production typically increasing inward from its margins, reflecting variations observed in other granodioritic plutons elsewhere. It is indeed possible that the adjoining dioritic rocks, hitherto assigned to other minor intrusions of similar age, located around the periphery of the Štiavnica pluton, in reality provide further evidence for zonation of the same pluton. The vicinity of this pluton is associated with surface heat flow ~ 40 mW m− 2 above the regional background. On the basis of our heat production measurements, we thus infer that the pluton has a substantial vertical extent, our preferred estimate for the scale depth for its downward decrease in radioactive heat production being ~ 8 km. Nonetheless, this pluton lacks any significant negative Bouguer gravity anomaly. We attribute this to the effect of the surrounding volcanic caldera, filled with relatively low-density lavas, ‘masking’ the pluton's own gravity anomaly. We envisage that emplacement occurred when the pluton was much hotter, and thus of lower density, than at present, its continued uplift, evident from the local geomorphology, being the isostatic consequence of localized erosion. The heat production in this intrusion evidently plays a significant role, hitherto unrecognized, in the regional geothermics

A meta-analysis of coal mining induced subsidence data and implications for their use in the carbon industry

Many empricial subsidence estimation tools exist worldwide but are designed and calibrated for specific coalfields. This paper presents an universal tool for the estimation of maximum subsidence (SMax). The subsidence tool is based on pooling and meta-analysis of empirical data from a number of different countries and coalfields. The key factors influencing SMax are the void dimensions and the mechanical competency of the overburden. These factors are used to estimate subsidence using the empirical equation SMax = [c/(1 + 10^(−a((W/D) − b)))] ∗m, where W is the width of the void, D the depth, m the effective void thickness, and a, b, c are parameters related to the mechanical competency of the overburden. This universial empirical method was validated against historical data from United Kingdom and Australia. The method also provided SMax estimations for underground coal gasification (UCG) projects, that were inline with those from numerical modelling under certain conditions. This tool would likely be most useful when investigating areas, where there are little or no historical data of subsidence and mining. Such areas are most likely to be targeted by UCG schemes

Life cycle assessment of the carbon intensity of deep geothermal heat systems : a case study from Scotland

Deep geothermal energy is widely recognised as a source of low carbon heat. However, to date there have been no specific assessment of the carbon intensity of low-enthalpy deep geothermal; previous studies focussed on geothermal power or higher enthalpy heat. As such, there is no established method for assessing the CO2 emissions from implementing a deep geothermal heating scheme. Here we address these gaps. We perform a life cycle assessment of greenhouse gas emissions relating to a deep geothermal heat system to (i) calculate the carbon intensity of geothermal heat; (ii) identify key factors affecting these values; (iii) consider the carbon abated if geothermal heat substitutes conventional heating; and (iv) present information that future projects can apply to assess the carbon emissions reduction offered by geothermal heat development. Our work is informed by parameters from a feasibility study for a proposed geothermal heat system in Banchory, Scotland. The project planned a 2.5 MWth geothermal plant extracting heat from the Hill of Fare granite via two boreholes, one injection and one production. We find that the majority of the emissions are associated with site construction, and sensitive to site and materials specific factors, for example the depth of the drilled boreholes and type and quantities of steel and cement used to seal them, or soils disturbed for laying pipelines and constructing access roads. During operation the carbon intensity of the electricity grid used to power hydraulic pumps largely determines the carbon intensity of the produced heat. We calculate that the carbon intensity of the heat produced is 9.7–14.0 kg(CO2e) MWhth which is 4.9–7.3% of the emissions from heat from natural gas. These values are compatible with Scotland's plans for long term decarbonisation of heat in line with national emission reduction obligations and would likely be compatible with any country's decarbonisation goals

Renewing the Exploration Approach for Mid-Enthalpy Systems: Examples from Northern England and Scotland

After a promising start in the 1970s and 80s, the UK rather fell behind other countries in the search for viable mid-enthalpy geothermal resources. This situation began to turn around in 2004, when the first of three deep geothermal exploration boreholes were drilled in northern England. What distinguished these from earlier drilling in Cornwall was the deliberate search for naturallyhigh permeability associated with major faults, especially those that have undergone strike-slip reactivation during the Cenozoic. Boreholes at Eastgate in the North Pennines targeted buried radiothermal granite, whereas the 1,821m-deep Science Central Borehole in Newcastle upon Tyne targeted a postulated deep sedimentary aquifer (the Fell Sandstones), which were inferred to be connected laterally to the granitic heat source by a major fault (the reactivation of the Iapetus geo-suture). The drilling was in both cases rewarded with impressive heat flows, and in the case of Eastgate with what is believed to be the highest permeability yet found in a deep granite batholith anywhere in the world. In parallel with these developments, a re-assessment was made of the preexisting geothermal heat flow database for the UK, applying newly-standardised correction protocols for palaeoclimatic and topographic distortions, which were found to be particularly marked in Scotland (where only shallow boreholes had been used to establish geothermal gradients in the original 1980s analysis), Similar prospects in northern England (similar to that drilled at Science Central) are now the focus of commercial exploration efforts. Appraisal of fault dispositions relative to the present-day maximum compressive stress azimuth are being used to identify the most promising areas for intersecting fault-related permeability at depth. New geophysical tools – most notably atomic dielectric resonance scanning – are also being appraised for their ability to directly detect features (such as hot brines) which are indicative of localised convection in target fault zones and aquifers

Cities in decline? A comparative history of Malmo and Newcastle after 1945

No abstract available

Recovery Factor of Geothermal Resources

No abstract available

How binding are legal limits? Transitions from temporary to permanent work in Spain

Includes bibliographical references. Also available via the InternetSIGLEAvailable from British Library Document Supply Centre- DSC:3597. 9512(no 3931) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Renewing the Exploration Approach for Mid-Enthalpy Geothermal Systems: Examples from Northern England and Scotland

ABSTRACT After a promising start in the 1970s and 80s, the UK rather fell behind other countries in the search for viable mid-enthalpy geothermal resources. This situation began to turn around in 2004, when the first of three deep geothermal exploration boreholes were drilled in northern England. What distinguished these from earlier drilling in Cornwall was the deliberate search for naturallyhigh permeability associated with major faults, especially those that have undergone strike-slip reactivation during the Cenozoic. Boreholes at Eastgate in the North Pennines targeted buried radiothermal granite, whereas the 1,821m-deep Science Central Borehole in Newcastle upon Tyne targeted a postulated deep sedimentary aquifer (the Fell Sandstones), which were inferred to be connected laterally to the granitic heat source by a major fault (the reactivation of the Iapetus geo-suture). The drilling was in both cases rewarded with impressive heat flows, and in the case of Eastgate with what is believed to be the highest permeability yet found in a deep granite batholith anywhere in the world. In parallel with these developments, a re-assessment was made of the preexisting geothermal heat flow database for the UK, applying newly-standardised correction protocols for palaeoclimatic and topographic distortions, which were found to be particularly marked in Scotland (where only shallow boreholes had been used to establish geothermal gradients in the original 1980s analysis), Similar prospects in northern England (similar to that drilled at Science Central) are now the focus of commercial exploration efforts. Appraisal of fault dispositions relative to the present-day maximum compressive stress azimuth are being used to identify the most promising areas for intersecting fault-related permeability at depth. New geophysical tools -most notably atomic dielectric resonance scanning -are also being appraised for their ability to directly detect features (such as hot brines) which are indicative of localised convection in target fault zones and aquifers. INTRODUCTION After a promising start in geothermal exploration and resource quantification in the 1970s and 1980s (Downing and Gray 1986a,b