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6 month review.pptx
- 1. QUADRAT DTP funded PhD 'The Low Enthalpy Geothermal Potential of Shallow Aquifers in Northern Ireland.' Bryan Magwood Murlough Bay with windblown sand on the right. Potential lo©Sean Barden
- 2. Project Outline 3 main aims: a) audit the shallow geothermal resource, b) to grade areas based on their economic heat source potential and, if possible, 3) to progress options to a high-level business case. 2 Develop a set of screening criteria for sites based on environmental, economic and geological conditions Focus areas will be geologically mapped to determine aquifer characteristics. Establishing the depositional environment to assess porosity and permeability distribution -> reservoir modelling and simulation, Use the map to identify focus areas which will be subject to more detailed study including the use of a suite of shallow geophysical techniques to constrain depth to bedrock, gravel aquifer internal properties and fluid content -> will provide detailed site-specific subsurface models, Use maps provided by the GSNI to create a shallow aquifer geothermal potential map, Initial desktop study of shallow gravel aquifers in NI (review sedimentology),
- 3. Geothermal Energy in NI • Geothermal energy can make a significant contribution to the energy transition in Northern Ireland. • This could be through shallow geothermal heating and cooling, • Deep geothermal for heat networks, or, if hot enough, power generation. • Heating is responsible for 50% of NI’s energy consumption, • 68% of homes in NI are heated by oil-fired central heating -> high in CO2 emissions. • Critical for our Energy Security! (DfE, 2020)
- 4. NI Energy Strategy • Contributed to the new NI Energy Strategy through my MSc research in NI deep geothermal in the Sherwood sandstone. • 3 points of the action plan relating to geothermal / low carbon heating technology which this project seeks to utilise. 4 (DfE, 2021)
- 5. Shallow >200m Geothermal • At shallow depths the groundwater temperatures are influenced by ambient air temperature at the ground surface and energy is replenished by solar radiation and groundwater movement. • Temperate climates (NI) there is considerable seasonal variation in air temperature, with monthly average temperatures ranging from about 3 ℃ in January to 16 ℃ in July. • Thermal properties of superficial sediments across the UK ensure subsurface temperatures do not fluctuate to the same degree and become relatively stable at depths of a few metres. • In NI, the subsurface temperature at about 10 metres depth has the range 10.5–11.4 ℃ (Busby, 2015). • This temperature is much lower than that required for domestic space heating, GSHPs are an efficient means of increasing the heat of the water to the required temperature and are a proven and reliable technology. Seasonal variation in average monthly subsurface temperatures with depth for the south of England (Sani et al., 2019).
- 6. 6 • closed-loop GSHP systems (either horizontal or vertical), (heating and/or cooling). • shallow aquifer open-loop systems (heating and/or cooling, aquifer thermal energy storage). • mine water energy (heating and/or cooling, thermal energy storage). The shallow geothermal heat resource beneath Northern Ireland can be considered in terms of three main geological settings and types of deployment:
- 7. 7
- 8. Glacial Sedimentology Summary of my findings in glacial sedimentology 8 Meltwater down cutting through end-moraine deposits, Thompson Glacier, Canadian Arctic, http://libwiki.mcmaster.ca
- 9. Glaciogenic Reservoirs Glaciogenic deposition can be divided into three depositional zones controlled by the ice margin position (1st order deposition control): 1. Subglacial zone where glacial erosion and deposition is responsible for the formation of a unique landform and sediment assemblage. It can be further subdivided in areas of slow-moving and fast-moving ice. 2. Ice marginal zone, where a mix of subglacial and proglacial processes occur. 3. Proglacial zone, where no direct influence of ice contact on sediment deposition can be seen. 9 (Kurjański et al., 2020)
- 10. Glaciogenic sedimentation is also affected by the depositional environment where the ice sheet terminates (2nd order control.) These depositional environments include: 1. Terrestrial - subaerially exposed land surface (including kettle hole and small proglacial lakes). 2. Large proglacial lacustrine – continental-scale lakes. 3. Shallow marine – from the shore to the shelf break. 4. Deep marine - beyond the shelf break. Finally, deposition is also controlled by ice sheet dynamics and can be further subdivided into: 1. Deposition during ice advance when sediment incorporation and advection is dominant, and less meltwater is released. 2. Deposition during ice retreat when sediment release and meltwater processes are dominant. 10 (Kurjański et al., 2020)
- 11. 11 Terrestrial good res depo environments: Pitted, Distal & Proximal sandur, Valley train/ ice marginal streamway, Glacier fed delta topsets, Aeolian dunes, Eskers Water terminating good res depo environments: Ice contact delta topsets, Ice contact delta foresets, Glacier fed deltas foresets, Subaqueous outwash fan (Kurjański et al., 2020)
- 12. Glaciofluvial 12 • Sandur / Outwash plain -> a large sediment body deposited by glacial, braided, meltwater streams in front of an ice terminus. Highly variable sediment thickness which depends on topography. Well-sorted, rounded to sub-rounded sands and gravels. Pitted, Proximal and Distal deposits all good. • Ice marginal streamway -> large ice front parallel fluvial system develops from meltwater escaping the ice sheet. Forms perpendicular to the sandur. Well-sorted fluvial sands and gravels and over bank deposits. Looks like typical fluvial succession. • Esker -> Sinuous glaciofluvial sediment ridges. Delineate sub, supra and englacial drainage pathways. Sediment fill of a meltwater channel. Erosional contacts (GES) present. Fans may develop at the end of an esker when it escapes the icesheet. Glaciotectonic signatures present with normal faulting with the loss of lateral ice support. Moderately / well-sorted boulders with subordinate sand. • Aeolian dunes (wind blown sand) -> wind reworking of sandur plains prior to the onset of vegetation. Fine-medium sand that are well-sorted.
- 13. 13 • Subaqueous outwash fan -> large sed body composed of sand and gravel deposited by glacial meltwater entering a waterbody at the grounding line of an ice sheet. The sed is deposited deep enough to prevent the fan from reaching the surface and forming an ice-contact delta. Well-sorted sands with silt + mud interbeds in the distal part. • Glacier-fed delta -> sandur enters waterbody forming a glacier fed delta. Long and wide with thickness controlled by water depth. Well-sorted sands with gravels in the foresets. Unconformably lain by topsets that are coarser and resemble sandur successions. Prodelta (distal) contains muds. • Ice-contact delta -> develop where subaqueous outwash fan fills accommodation space between sea bed and water surface. Geometry of the delta is controlled by the ice margin and may not exhibit typical d shape of the delta. Well-sorted sands with gravels in the foresets. Unconformably lain by topsets that are coarser and resemble sandur successions. Prodelta distal contains muds. Buoyant sediment plume -> increased density of seawater. Glaciolacustrine/Glaciomarine Glacial Delta top set and foreset beds (Johnsen and Brennand, 2006)
- 14. 14 Mourne Plain and area visited highlighted in red Kilkeel Beach Fieldtrip (GSNI, 2006)
- 15. 15
- 16. 16 Facies found include: • Till, • Gravel, • Sand Kilkeel Steps
- 17. Geothermal Potential Map My current progress with the map 17
- 18. 18 The map displays only the surface extent of permeable rock units and many of these are present below other rock units at relatively shallow depth, thus extending the area available significantly.
- 20. Map Future Work • Acquire borehole data from GSNI – already have a list produced for around Belfast area to calculate saturated aquifer thickness. GSNI busy until April (getting borehole data then). • Use borehole data to create groundwater table layer. This will change the map from reservoir quality map (suitability for open-loop systems map) to shallow aquifer potential map. • Once saturated aquifer thickness acquired -> aquifer volume determined (saturated thickness x surface area = volume). • Determine total heat in place, • Determine recoverable heat. The amount of heat (G) extractable from flowing water is • G = F *ΔT * SVCwat; • where F = flux of water (kg/s), • ΔT = difference between the inlet and outlet temperature in the heat pump (K) and • SVCwat = heat capacity of water (J/kg · K) • Potentially use this recoverable heat to create a shallow aquifer potential map that shows aquifers that can supply greater than 100 kW heating/cooling. 20
- 21. Heat Demand 22
- 22. Malone Sands – Lagan Valley (Greater Belfast) 23 • Comprised of the Malone Delta, eskers and an outwash plain. • A lot of the sed resides under greater Belfast area. Good for retrofitting buildings to utilise the shallow geothermal resource and for future greenfield developments. • Sed was depo in the Midlandian and involved interaction from 2 ice sheets. • Irish Ice cap in the West and Scottish in the East (blocking Belfast Lough). • During retreat meltwater flooded Lagan Valley -> Glacial Lough Lagan. Meltwater sed derived from Triassic Sherwood SST, forming Malone delta. • Delta Topsets, Foresets and Eskers good targets. Located in the South.
- 23. Summary • Proglacial meltwater derived glaciogenic sediments provide the most prospective reservoirs. Typically high hydraulic conductivity of glaciofluvial sand/gravel aquifers as seen in Finland (between 10−5 and 10−2 m/s) (Salonen et al. 2014; Salonen et al. 2001), which allows for a relatively high groundwater abstraction & injection rate -> high COP. • Suitable chemical properties of the groundwater, i.e. low concentrations of Fe, Mn, CO2 & Cl−, are essential to avoid clogging and corrosion of the GSHP system (Sanner 2001). • Geothermal aquifer potential map underway, reservoir quality map produced. Now to produce a shallow aquifer map (with aquifers able to provide over 100 kW of heating/cooling included?) • Some suitable locations identified for further research and greater focus -> Malone sands delta Greater Belfast and Kilkeel glacial outwash plain. • Once the map is further in progress, can begin to start planning site-specific visits for geological mapping and geophysical characterisation (GPR, shallow seismic reflection & refraction). 24
- 24. The end Thanks for listening 25
Editor's Notes
- Initial desktop study of shallow gravel aquifers in NI, Use maps provided by the GSNI to create a shallow aquifer geothermal potential map, Use the map to identify focus areas which will be subject to more detailed study including the use of a suite of shallow geophysical techniques to constrain depth to bedrock, gravel aquifer internal properties and fluid content. Shallow seismic reflection and refraction, passive seismic surface wave, resistivity tomography and GPR -> will provide detailed site-specific subsurface models, Focus areas will be geologically mapped to determine aquifer characteristics. Establishing the depositional environment to assess porosity and permeability distribution. Develop a set of screening criteria for sites based on environmental, economic and geological conditions -> for replication elsewhere.
- 68% of homes using oil fired central heating represents a significant decarbonisation challenge. Geothermal is the solution.
- I’ll speak abit about the new Energy Strategy for NI which was published in December 2021. It outlines a roadmap to 2050 aiming to achieve net zero. My MSc project was carried out in collaboration with the GSNI/ DfE and contributed to this. There are 22 points making up the action plan and 3 directly relate to geothermal energy or low carbon heating showing government backing for this technology. Point 15 highlights a low carbon heat demonstrator project and the work of this PhD could feed directly into this and the business case developed. Shows that geothermal is blossoming in NI with the policy and strategy to support the technology.
- Groundwater can be exploited to supply the heating and/or cooling demands of residential households or industries. The low enthalpy energy in shallow aquifers, typically below 200 m in depth, indicates an energy resource in which the temperature is below 30°C (Banks 2010). This geothermal energy is mostly derived from solar radiation (Fetter 1994), as only a minor proportion of stored energy in shallow aquifers originates from the Earth's internal heat (Banks 2010). Several studies have demonstrated that shallow aquifers under cities can be a significant low enthalpy energy source (Allen et al. 2003).
- The variety of shallow GSHP systems allows for deployment in a wide variety of geological scenarios. This project will focus on utilising open loop technology and tackling the issue of poor subsurface understanding and reducing the risk. NI has very limited mine water geothermal potential so focus should be entirely on shallow aquifer geothermal for utilisation by open-loop technology.
- So now we will look at the shallow geology of NI. I am showing this map to highlight that 85% of the land surface in NI is covered by glaciogenic sediments. A barrier to open loop GSHP sytems has been subsurface risk. This can be addressed by understanding glacial sedimentology to comprehend what depositional environments yield suitable facies for a productive geothermal aquifer. So I have conducted a review of glacial sedimentology.
- The Irish landmass has undergone repeated glaciations during the Pleistocene period. Glacial processes control the distribution of glaciogenic sediments and landforms. These Glaciogenic packages are less well understood and often underexplored for their reservoir potential than sediments associated with more “typical” depositional environments. It is important to understand reservoir heterogeneity, connectivity and barriers to fluid flow in the subsurface. Sequence stratigraphy and the concept of system tracts is of use when interpreting glaciogenic deposits. But unlike traditional sequence strat, accommodation isn’t linked to the RSL changes but instead the ice margin position exerts the primary control on accommodation and mode of deposition. Ice advance controls marine regression and ice retreat controls marine transgression. This is complicated by glacial isostatic adjustment, forebulge collapse and eustatic sea level changes, all effect the sed package resulting in a high lateral variability of deposition.
- Figure here shows depositional environments with their associated reservoir quality. Whether variable reservoir quality deposits can be classified as good or bad depends on: -the stage in ice sheet dynamics they are deposited in (advance/retreat/stillstand), -the sediment available for reworking (previously deposited sed). So, if this was glaciofluvial the reservoir quality will typically be good and if traction till is reworked the sediment will be poor. This is important to consider for moraine deposits. Erosional features are important sites of deposition to consider. Features formed during an ice advance e.g. tunnel valley will be filled with glacial meltwater derived sed during retreat, which could be a good target. These will likely be buried.
- Glaciofluvial deposits with good reservoir quality include: Sandur / Outwash plain -> sediment body deposited by glacial, braided, meltwater streams in front ice. Highly variable sediment thickness which depends on topography. Well-sorted, rounded to sub-rounded sands and gravels. Pitted, Proximal and Distal deposits all good. Ice marginal streamway -> large ice front parallel fluvial systems. Forms perpendicular to the sandur. Well-sorted fluvial sands and gravels and over bank deposits. Looks like typical fluvial succession. Esker -> Sinuous glaciofluvial sediment ridges. Delineate drainage pathways. Sediment fill of a meltwater channel. Erosional contacts (GES) present. Fans may develop at the end of an esker when it escapes the icesheet. Moderately / well-sorted boulders with subordinate sand. Aeolian dunes or wind blown sand are not glaciofluvial but formed by wind reworking of sandur plains prior to the onset of vegetation. Fine-medium sand that are well-sorted.
- Subaqueous outwash fan -> sed body composed of sand and gravel deposited by glacial meltwater entering a waterbody at the grounding line of an ice sheet. The sed is deposited deep enough to prevent the fan from reaching the surface and forming an ice-contact delta. Well-sorted sands with silt + mud interbeds in the distal part. Glacier-fed delta -> sandur enters waterbody forming a glacier fed delta. Long and wide with thickness controlled by water depth. Well-sorted sands with gravels in the foresets. Unconformably lain by topsets that are coarser and resemble sandur successions. Prodelta (distal) contains muds. Ice-contact delta -> develop where subaqueous outwash fan fills accommodation space between sea bed and water surface. Well-sorted sands with gravels in the foresets. Unconformably lain by topsets that are coarser and resemble sandur successions. Prodelta distal contains muds.
- Went on a fieldtrip to visit outcrops to better understand reservoir architecture and glacial deposition processes. This area is located in the South east of NI and is a basin known as the mourne plain. The glaciogenic deposits here where deposited by the actions of three separate ice flows. The coastline crosscuts the deposits and allows for a cross-section view into the reservoir architecture and geometry of glaciofluvial and glaciomarine sediments. The location and relative stability (rate of retreat) of these ice margins together with ice marginal input and variability of tidewater processes controlled the facies sequences found within the basin.
- The photo here shows a cross-section through a glaciogenic sequence. With glaciomarine mud and diamicton present at the base, overlain by glaciofluvial sands and gravels. The gravel pocket likely represents an outwash fan as the subglacial channel exited the ice. With the sand around it being cross bedded indicating barforms in a glaciofluvial outwash plain. A thin layer of clean sand is present above this representing aeolian windblown sand which has a sheet like geometry. This is from the reworking of outwash plain sands. Above this it returns to a proglacial outwash plain. The facies changes are due to a combination of ice margin oscillation and isostatic equilibrium after ice sheet retreat. This was good for picturing reservoir geometries and to understand the thicknesses of sed deposited.
- This image is 1km further along the coast, where three lithofacies are identified including gravel, sand and glaciomarine mud. The images show a large channel which has cut into the mud beneath. This channel has a gravel lag which is size sorted. The gravel at the base is boulder sized and fines upwards into a sand. The deposit represents a point bar. Likely deposited in the proximal zone of a outwash plain/sandur. The rest of the channel is filled with planar laminated sand representing channel fill. Above this lies a very clean laminated, well sorted, fine to medium sized sandstone. The sandstone is crossbedded in places and occurs as a tabular unit across the cliffs, tapering out to the NE. The sand is the product of aeolian reworking of sed deposited on the sandur. The gravel above has in places scoured the ‘clean’ sand beneath, representing braided channels of a proximal sandur. The gravel is stratified, laminated and some sections exhibit reverse graded bedding packages. The succession above the mud represents a good reservoir target.
- So now we know what makes a good reservoir lets look at the map I have been developing in QGIS.
- This is the current progress with the map. It represents a reservoir quality map and my research into glacial sedimentology can explain the reasoning behind why certain deposits and landforms are shown on the map. The map has urban areas overlain to illustrate what areas are in proximity to good reservoir quality units, which could form potential aquifers. Alluvium represents bank and overbank deposits (channel/floodplain sands and muds) which have typically good reservoir quality so are included. Glaciofluvial/lacustrine sand and gravel are included due to sediments being derived from meltwater representing good reservoir characteristics. The targets where previously discussed. Windblown sand is included due to the good reservoir characteristics of aeolian sand. Till is omitted due to the very poor reservoir quality observed. Various geomorphological landforms are shown on the map. Drumlins are typically formed of smoothed traction till deposited in the subglacial zone by fast flowing ice. They are shown on the map as pink lines. They themselves represent poor reservoir quality targets, but at the base of the slope of the drumlin or between two drumlins in the trough is where meltwater flows under the ice sheet. This results in the deposition of sediment known as an intra till sand and gravel. This is relatively small but if saturated could constitute a suitable aquifer for a small housing development. Eskers are shown on the map as purple to understand the makeup of glaciofluvial sand and gravel, but also to show stand alone good reservoir targets. Moraines are shown (brown lines) and their reservoir quality depends on the origin of the sediment that has been reworked to form the moraine. So if ice advance has occurred and an outwash plain has been bulldozed and reworked. The good sediment sorting and roundness can be preserved in a push moraine deposit, although not all moraines preserve this so it is important to understand how the moraine was formed. If the ice reworks traction till to form a moraine then the reservoir quality will be poor. I included moraines as some can form good reservoirs and they help understand the makeup of glaciofluvial/lacustrine sand and gravel deposits on the map. That is essentially this map, I have focussed entirely on superficial deposits as work is already being conducted on the Sherwood sandstone under Belfast at QUB. From this I have identified two areas with potential for future investigation. 1. Kilkeel where I went on the fieldtrip to and 2. Greater Belfast area which overlies deltaic sands. I have another slide on this later.
- I created a Traffic light map to show if shallow open loop geothermal installations are generally possible based on expected reservoir quality. A EU funded shallow geothermal potential project started by mapping this and showing it on traffic light maps. The sediments I spoke about on the last slide constitute good reservoir quality, with additional info required referring to estuarine and lacustrine sediments, and poor reservoir quality constituting till. These reservoir quality maps do not show geothermal potential as the reservoirs must be saturated to have geothermal potential. Where these good reservoir quality sediments intersect the water table and are saturated with water, is where there will be geothermal potential. This must be mapped. The reservoir quality map must then be modified using available borehole data to highlight which aquifers are saturated and adjust the boundaries accordingly. Borehole data will show the height of the water table and at what depth it intersects the sediment. With the aquifer surface area, the saturated volume of the aquifer can be calculated.
- 3 parts of the energy calculations I want to do. 1. Heat power extractable from the groundwater flow (amount of heat, G) calculated to describe the potential groundwater heating capacity of NI. 2. The amount of recoverable heat power transportable to a space-heating unit using GSHP systems (total heat load, H) was then calculated. 3. Calculate approx the area (m2) of residential buildings that could be heated using groundwater heating power. Calculations for each mapped urban area located inside a groundwater area.
- Heat demand map of NI. This illustrates the areas of large heat demand. Where an area of high heat demand overlies a superficial aquifer, there is potential for exploitation of the shallow geothermal resource in an open loop district heat network with each heat user having a heat pump.