November/December Reservoir 2023

NOV/DEC 2023 • ISSUE 6 • VOL 50

THE MAGAZINE OF CANADIAN ENERGY GEOSCIENTISTS

Reservoir cegageos.ca

In This Issue

NOV/DEC 2023

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Petrophysics in the Green Economy – Part 9: Metallic Minerals: Subsurface Methods

14 Sampling Microbes from Drilling Rigs 20 2023 Field Trip Season in Review 22 From the Desk of the AER 26 Geology in Motion: The Geology of the Battle of Vimy Ridge

CONFERENCES

UPCOMING EVENTS

PAGE 23

PAGES 18

EETIG 2024

EVENTS INFORMATION BEST SUB-CATEGORY PHOTO – METAMORPHIC TEXTURE Crenulated muscovite schist, British Columbia. Thin section of a lower amphibolite facies regionally metamorphosed schist from southwest of Kimberley in the Purcell Anticlinorium on the eastern margin of the Omineca Belt. The protolith of the schist was a Mesoproterozoic (~1.47 Ga) turbidite of the Aldridge Formation that was deformed and metamorphosed during the Mesoproterozoic East Kootenay Orogeny (~1.35 Ga) producing a primary planar, schistose fabric defined by flattened quartz grains (shades of grey) and strongly oriented muscovite crystals (elongate crystals with bright colours). During the Mesozoic (~0.15 Ga), compressional deformation associated with Cordilleran orogenesis was superimposed giving rise to the microscopic chevron folds. Width of field of view 6 mm, crossed polars.

Photo by: Dave Pattison

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FROM THE EDITOR SARAH SCHULTZ, TECHNICAL EDITOR FOR THE RESERVOIR

WELCOME TO THE NOVEMBER/DECEMBER ISSUE OF THE CEGA RESERVOIR! This year has flown by, and we are already at our final issue for the 2023 year! We have had some great content submitted to the Reservoir this year and we are looking forward to seeing what 2024 brings.

In this issue we have the continuation of our regular articles: • E.R. Crain’s Part 9 of the Petrophysics in the Green Economy series • Geology in Motion – The Geology of the Battle of Vimy Ridge • From the Desk of the AER – Quantifying Alberta’s Geothermal Resources

We present the following technical articles: • Stancliffe et al. – Sampling Microbes from Drilling Rigs • Pinnow – 2023 Field Trip Review Registration is open for the 2nd edition of the EETiG Symposium in Calgary, Alberta from February 7 – 8, 2024. This year’s event is themed “Adventures in Pore Space: Shared Reservoirs in New Energy”.

Thank you to everyone who attended CEGA events over this past year! Please refer to the CEGA website for up-to-date information on upcoming division talks, conferences, and technical webinars in the new year.

We look forward to continuing to receive your manuscripts for our 2024 Reservoir Editions!

Sarah Schultz PUBLICATIONS INFORMATION The RESERVOIR is published 6 times per year by the Canadian Energy Geoscience Association. The purpose of the RESERVOIR is to publicize the Society’s many activities and to promote the geosciences. We look for both technical and non-technical material to publish.

The contents of this publication may not be reproduced either in part or in full without the consent of the publisher.

No official endorsement or sponsorship by the CEGA is implied

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for any advertisement, insert, or article that appears in the RESERVOIR unless otherwise noted. All submitted materials are reviewed by the editor. We reserve the right to edit all submissions, including letters to the Editor. Submissions must include your name, address, and membership number (if applicable). The material contained in this publication is intended for informational use only.

While reasonable care has been taken, authors and the CEGA make no guarantees that any of the equations, schematics, or

devices discussed will perform as expected or that they will give the desired results. Some information contained herein may be inaccurate or may vary from standard measurements.

The CEGA expressly disclaims any and all liability for the acts, omissions, or conduct of any third-party user of information contained in this publication. Under no circumstances shall the CEGA and its officers, directors, employees, and agents be liable for any injury, loss, damage, or expense arising in any manner whatsoever from the acts, omissions, or conduct of any third-party user.

BOARD OF DIRECTORS 2023

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RESERVOIR ISSUE 6 • NOV/DEC 2023

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Petrophysics in the Green Economy

PART 9

METALLIC MINERALS: SUBSURFACE METHODS E. R. CRAIN, P.ENG. ACCESSIBLE PETROPHYSICS LTD. SANDRA BLEUE, PETROPHYSICS OUTSOURCE INC.

INTRODUCTION For this article, we are expanding the definition of petrophysics to include the exploration methods performed on or near the surface to locate potential ore bodies, using all the physical principles from oilfield well logging experiences. The next article, the last in our Green Economy Series, covers borehole logging in the mining environment.

But first, a little background to set the stage.

In 2023, the International Energy Agency (IEA), stated that “to reach net-zero emissions by 2050, we need to be producing six times the current global output of minerals just to build the turbines, transmission lines, batteries, and other items essential for lowcarbon energy infrastructure.”(1) Instead, we are mining less than we did in 2019. A reading of the Pan-Canadian Geoscience Strategy (PGS), outlined in Natural Resources Canada’s report, “The Canadian Minerals and Metals Action Plan 2020 (CMMP),” might hold some clues. By 2017, it was posited that a strategy was needed “to develop next generation geoscience knowledge and tools to efficiently target higher-grade or deeper deposits,” with the ultimate goal being a mine of the future that produces zero waste.(2) Zero waste may be a bit of a stretch. Regardless, new mines are urgently needed and we already

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have the tools and the petrophysical skills to use them. There are a surprising number of tools and analysis techniques available. No single one is a “magic-bullet”, although some combinations may come close.

The first Secret to Success is to choose the appropriate tools and integrate the results to gain the best possible understanding of the potential ore body. The second is to combine the talents of both mining and petroleum geoscientists to encourage collaborative and innovative solutions to the search for critical minerals.

SEISMIC ACQUISITION FOR MINING APPLICATIONS While the petroleum industry used seismic as its primary exploration tool for a hundred years, it wasn’t until 1993 that the Geological Survey of Canada began applying acoustic

technology to mineral exploration. Seismic had been viewed as too expensive, the terrain too challenging, and the coupling of the receivers to hard ground too uncertain to merit serious consideration. However, with the depletion of near surface ore bodies, these objections needed re-evaluation. The burning question was, is the acoustic impedance between ore body and host rock large enough to generate a reflection?

Data was collected in various mining locales, including mineral samples from various deposits for lab analysis, followed by the acquisition of well logs, offset VSP surveys and eventually 2D multi-channel seismic surveys. Special care was taken to adjust for pressure differences between lab and subsurface, and to determine if the high frequency, short propagation paths characteristic of logging data could match the lower frequencies in a seismic survey. The results were promising, and acoustic data

FIGURE 1: Horizontalgradient magnetic map of Alberta showing lineaments (white lines).

After Lyatsky et al., 2005.(3)

FIGURE 2: Magnetotelluric site in Oregon.

A magneto-telluric system is connected to a magnetometer and two sets of electrodes to collect magnetic and electric field data.(6)

is now used to map lithologies, detect ore bodies, and find permeable zones (such as sulphide mineralization controlled by fluid flow through faults), using full waveform acoustic logs to help interpret seismic reflections.

Vertical seismic profiles should also be considered as they “see” below the bottom of the borehole and a considerable distance beside the hole. A density log is also recommended to allow more accurate calculation of acoustic impedance for seismic modeling and tomography.

POTENTIAL FIELD METHODS Surface seismic surveys rely on acoustic impedance (density times seismic velocity) contrasts across a geologic boundary. Other surface methods are employed which exploit changes in rock density or naturally occurring geomagnetic waves. These methods tend to cover large areas and have poor resolution; despite these downsides, they are most effective when used in conjunction with seismic. While seismic detects near-horizontal rock boundaries, gravity and magnetics are better for steep discontinuities such as faults.(3)

GRAVITY FIELD MAPPING AND DATA PROCESSING These surveys, which locate anomalous rock density, can be acquired on land or water and tend to be popular in frontier areas.

The main purpose of a gravity survey is to define lithology, structure, and potential ore

bodies. These methods have benefitted from the widespread use of GPS; GPS antennas can be placed on receivers and transmitters in airborne systems. Gravity surveys have been used with magneto-telluric (MT) surveys and magnetics to map basalt covered sediments (4).

Corrections for station elevation, surrounding terrain elevation using digital surface maps and digital Hammer Charts, and Bouguer Anomaly are required. Subtraction of a 3rd order regional surface from the corrected data set will give a contour map of the Bouguer gravity anomaly, which can be used to plan next steps in the exploration program.(5)

MAGNETO-TELLURICS (MT) This passive geophysical method measures the naturally occurring electromagnetic waves generated by solar wind and lightning above the earth to image the subsurface in terms of resistivity. MT is used in remote areas as a lower cost alternative to seismic.

Surface receivers record horizontally and mutually orthogonal 2 components of electric and 3 components of the magnetic fields.

The variation and amplitude of the signals are interpreted using the magneto telluric impedance, Z. This method has been used since the 1950s. In recent time it is being used to explore for and monitor geothermal fields.

In 2018, the US began to compile an opensource repository of these data.(6)(7)

APPLIED CURRENT METHODS These methods have direct comparisons to well logging tools.

SUBSURFACE RESISTIVITY MAPPING

Subsurface resistivity measurements are made using electrodes planted in the ground and a power source. Different electrode arrays vary, with a dozen or so well documented arrangements. Electrode arrays were developed in order to make field measurements more efficient and data interpretation easier.

SCHLUMBERGER ARRAY This subsurface geophysical exploration method using induced electrical current was developed by Conrad Schlumberger in the early 1900s. He used direct current (DC), but the polarity was reversed at a rate that prevented charge buildup in the ground. Two current electrodes were driven into the ground some 50 to 200 metres apart. Two measure electrodes were placed symmetrically between and inline with the current electrodes, some distance away from the current electrodes to prevent “edge effects”. The voltage measured was inversely proportional to the resistivity of the ground between the measure electrodes.

The depth of penetration of the measurement increased with increased electrode spacing, so multiple spacings were run to obtain a “3-D” image of the subsurface resistivity.

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FIGURE 3: Combined data from ERT survey (A) and IP model (B) to detect narrow galena veins in granite.

Model A clearly distinguishes the sedimentary cover from the granite; IP anomalies show the veins.(8)

FIGURE 4: The left side of the diagram shows current potential lines in a homogeneous material; to the right, equipotential lines are distorted by a conductive ore body, which pushes the lines away, roughly delineating the ore mass.(9)

FIGURE 5: Simplified acquisition scheme for apparent chargeability and resistivity.(10)

In sediments, low values could mean aquifers or clay/shale beds; higher values suggested hydrocarbons or tight rock. In hard-rock country, low resistivity suggested massive sulphides or metallic minerals. Other uses include clay alteration around hydrothermal zones, lithology and structural controls on mineralization. Successful interpretation was not guaranteed. Awareness of this uncertainty led to more recent work where ERT (Electrical Resistivity Tomography) is acquired with IP survey data to successfully image galena veins within a granitic host rock, beneath a sedimentary cover layer, (Figure 3). (8)

This method is still in use today. Mise-a-la-Masse is unique because the conductive mass being examined is itself used as one current electrode, with a second current electrode placed 5-10 times distant from the size of the conductive volume being investigated. Current is injected across the current electrodes and the potential voltage distribution radiating outwards from the injection borehole gives an idea of the shape and volume of the mass. (9)

MISE-A-LA-MASSE ARRAY (MALM)

IP is an electromagnetic method in widespread use in the mining industry. It is a method to image the conductivity and chargeability of porous rocks. It is most commonly used to delineate disseminated and massive sulphides within a host rock.

Loosely translated from French, Mise-a-la-Masse means “charged body”.

This method was very popular in the 1920s and 1930s for searching out ore bodies. This technique is unique to mining; its purpose is to demarcate highly conductive masses such as sulphides and contaminant plumes.

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INDUCED POLARIZATION METHODS (IP)

For a 2D or 3D output, a Wenner-Schlumberger configuration selects combinations of electrodes in groups of four (two current electrodes and a pair of non-polarizable potential electrodes) applied on the ground.

Apparent chargeability and resistivity are recorded by each electrode and the measurement is assigned to a geometric depth in the ground (Figure 5).(10) When a charging current is turned off, the voltage decays over a finite time (discharging) back to zero. When the current is turned on, voltage builds up over a finite time to a maximum applied value. The current is, for a time, stored in the ground (capacitance), causing some material to become polarized.

This phenomenon is called induced polarization. Chargeability is affected by grain size, mineral type, mobility of ions in pore fluid, interactions between solid surfaces and fluids (such as clay particles in the fluid), and surface area of the material.

For example, illite, a clay, which has a much greater surface area than sandstone, tends to hold a charge, whereas the latter (a possible host rock) does not. IP surveys are useful in hydrogeology, to isolate saline water from clay, which both have low resistivity.

FIGURE 6: Induced Polarization in time domain showing a) on/ off time increments of inducing current, b) measured potential, c) overvoltage delay and d) calculation of apparent chargeability.(10)

Chargeability can be measured in the time domain, calculated as the normalized area underneath the decay curve (Figure 6d). The data are inverted, resulting in a resistivity model which quantifies the rock above the deposit and a chargeability model which images the deposit itself. Chargeability can be measured in both frequency and phase domains.(11) In the latter, the data is solved for MF, or metal factor, in Siemens per metre (S/m).(10) Multiple logs must be run for a definitive result. For example, disseminated sulphides, which gold deposits could be associated with, can be resistive or conductive, plus resistivity can appear lower due to either the presence of clays or ore minerals. There is a large range in chargeability between different materials, from 0 msec for groundwater, up to 30 msec in a Precambrian gneiss. For specific minerals, chargeability is dependent on the concentration within the host rock. There is a large spread of possible values, ranging from 13.4 msec in a 1% sample concentration of pyrite, down to 2.2 msec in a similar concentration of magnetite.

This anomalously high chargeability of pyrite has sparked a novel use for IP in hydrocarbon exploration. Minor amounts of hydrocarbon leaking through the top seal of a deeper hydrocarbon trap can form a pyrite rich alteration zone. These halo-shaped zones can be identified as anomalies with an IP survey, helping to reduce drilling costs.(12)

AEROMAGNETIC METHODS (EM, TEM)

FIGURE 7: TEM system waveforms: 2a) transmitter current, 2b) the induced electromotive force, 2c) the secondary current and magnetic field.(13)

These surveys can be acquired by aircraft flying a track or grid pattern at relatively low altitude, or on the ground. They measure spatial variations in Earth’s magnetic field over the surveyed area, which are usually related to mineralogy. The main objective of an aeromag survey is direct detection of iron ore, subsurface lithology, and structure, as well as the extent of permissive terranes (areas that can contain a certain type of mineral occurrence or ore deposit). It can be used to identify hazardous material from nickel/copper or asbestos in serpentine.

Like IP, TEM has been used to map geochemical anomalies and oil-water contacts in shallow hydrocarbon reservoirs - a lot of this investigation has been done in Russia.(4)

For helicopter-conveyed TEM, the transmitter coil is fixed to a rigid frame suspended beneath a helicopter, with a receiver positioned centrally within the frame. A DC current is run through the transmitter, then rapidly switched off, generating a square wave. This in turn generates a time-varying magnetic field in the subsurface which instigates eddy currents. These currents cause the onset of a secondary magnetic field. The receiver coil measures this secondary field’s strength and temporal response, and data is displayed as time/magnitude decay curves. The resultant time amplitude data is inverted to arrive at a resistivity image of the subsurface.

Like IP, the data can be represented in the time domain (TEM: Transient Electromagnetic), or the frequency domain (EM). In the frequency domain, a current is transmitted continuously as a single frequency, which works well for shallow targets.

When deployed by a fixed wing airplane, the receiver, or bird, is towed behind in an offset configuration. A ground-based system has a similar transmitter/ receiver arrangement as the helicopter, providing information about the ground directly beneath the loops.

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FIGURE 8: Contoured Aeromagnetic data (left), post-processed 3rd order residual map of same dataset (right).

Aeromag requires data corrections for flight altitude and flight track closure errors (preGOS only). Subtraction of a 3rd order regional surface from the corrected data set will give contour map of the magnetic anomaly. An optimized borehole drilling and coring program is derived from this map (Figure 8).(5) Unsurprisingly, electromagnetic measurements can be complicated by the IP effect. This occurs where the earth is neither acting as a resistive nor conductive body, but instead acts as a capacitor. In cases where this is known to be a problem, the data can be inverted using a special model that inverts not just for resistivity, but also for IP effects. A description of this workflow can be found in Grombacher et al., 2021.(14) Current trends in TEM involve complex forward modeling of massive sulphides, with a focus on recognizing various possible morphologies.(15)

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RADIOMETRIC FIELD MAPPING AND DATA PROCESSING These surveys can be acquired by aircraft or on the land surface. They measure natural occurring radiation from potassium, thorium, and uranium. Also known a gamma-ray spectrometry, their main purpose is direct detection of uranium prospects.

Thorium increases in felsic rocks, indicating alkalinity, which in turn provides an indication of oxidation of sulphides, leading to faster uranium mobilization. Potassium alteration associated with hydrothermal ore deposits can also be detected. Other uses include heat flow studies and environmental mapping.

Recorded data requires corrections for flight altitude and flight track closure errors (pre-

GPS only). Subtraction of a 3rd order regional surface from the corrected data set will give a contour map of the radiometric anomaly. It is interesting to note that combined airborne magnetic and radiometric surveys, being the most cost-effective geophysical survey method, have become a means to “stimulating mineral exploration” worldwide.(16)

ELECTROMAGNETIC SPECTRUM REMOTE SENSING These surveys record infra-red (IR), visible, and ultra-violet (UV) light emanating from the earth’s surface, usually acquired from air photos or satellite images from instruments with appropriate filters fit for the survey’s purpose.

Recent developments include surveying via drone, which provides a compromise between ground-based soil and

FIGURE 9: Model morphology of classic volcanic-associated massive sulphide deposit with central mound and discordant feeder along a synvolcanic fault.

rock sampling, and large-scale airborne surveys. This is important, given today’s eco-conscious attitude against mining. Hyperspectral (the continuous spectrum of reflected sunlight in the visible and near infra-red regions) imaging is being used to map rare-earthelement prone regions in Namibia.(17) Often used to locate anomalous vegetation which may indicate minerals in soil, EMS remote sensing is also used to identify chemical spills, tailings, pond leakage, other environmental damage, or to demonstrate successful environmental restoration.

CONCLUSIONS The examples shown in this article illustrate the possibilities for the integration of diverse data sets that can reduce the risk of misinterpretation and help to meet the objectives of an eco-friendlier industry.

The multiple and overlapping usages of surface exploration methods provide real solutions to real exploration issues.

The “petro” in Petrophysics means “rock”, not “petroleum”! The right kind of rock is what mining engineers, management, and shareholders are looking for. It is time to integrate all our petrophysical / geoscience skills to find those deeper prospects we know must be out there. Our world depends on our success.

FIGURE 10: A: Ternary radioelement map showing abundance K (red), Th (green), U (blue). B: IHS composite image.

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REFERENCES 1. Exner-Pirot, H. “Drop in mining deratils drive for Net Zero”. The National Post. https://epaper.nationalpost.com/article/281895892585033 (accessed May 11, 2023) 2. The Canadian Minerals and Metals Plan. “Action Plan 2020: Introducing the Pan-Canadian Initiatives”. https://www.resourcedata. org/dataset/23794a95-1cae-47fd-bbca-da003845fa1d/resource/ c4f58523-3a23-4f3f-b393-f63b1efa8f70/download/f6.pdf, (page 18) (accessed May 11, 2023) 3. Schulte, B.W., “Methods of fault detection with geophysical data and surface geology”, https://csegrecorder.com/assets/pdfs/2019/201909-RECORDER-Methods_of_fault_detection.pdf (accessed June 28, 2023).

4. Meju, M.A., “Geoelectromagnetic exploration for natural resources: Models, case studies and challenges.” Surveys in Geophysics, 23: 133-205 (2002) 5. Crain, E.R., Pratt, David, Bogehold, R., “Review of Gravity and Magnetic Data Processing Systems, CSEG Journal Vol 8 No 1 Dec 1972 6. Gupta, H., Roy, S., “Geothermal Energy”, 2007 7. Kelbert, A. et al, Ec Newsletter, https://eos.org/science-updates/ taking-magnetotelluric-data-out-of-the-drawer 27 December 2018 8. Martinez, J, Rey, J., Sandoval, S., Hidalgo, M.C., Mendoza, R. “Geophysical prospecting using ERT and IP techniques to locate galena veins.” www.mdpi.com/jornal/remotesensing. Remote Sens.

2019, 11, 2923; doi:10.3390/rs11242923 9. EPA Web Archive, Environmental Geophysics, “Equipotential and Mise-a-la-Masse Methods”, https://archive.epa.gov/esd/archive-

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geophysics/web/html/equipotential_and_mise-a-la-messe_methods. html (accessed June 12, 2023) 10. Marescot, L., “Electrical Surveying, Part II: Induced polarization method”, Swiss Federal Institute of Technology, Zurich, (accessed March 20, 2023) 11. University of British Columbia, “Introduction to induced polarization surveying” https://www.eoas.ubc.ca/courses/eosc350/content/ methods/meth_2/ip.pdf (accessed May 10, 2023) 12. SEG, “A review of some experience with the induced-polarization/ resistivity method for hydrocarbon surveys: Successes and limitations” https://library.seg.org/doi/10.1190/1.1442963 13. McNeill, J.D., “Applications of Transient Electromagnetic Techniques”. http://www.geonics.com/pdfs/technicalnotes/tn7.pdf Oct 1980 (accessed June 12, 2023) 14. Grombacher, D., et al, “Induced polarization effects in airborne transient electromagnetic data collected in the McMurdo Dry Valleys, Antarctica”. Geophysical Journal International, 2021, pg. 1574-1583.

15. Prikhodko, A., Mumin, H., “Electromagnetic responses to massive sulphide ore systems of various morphologies and conductivities.

CIM Journal Vol. 9, No. 4, 2018.

16. IAEA, Vienna“Guidelines for radioelement mapping using gamma ray spectrometry data”, https://www-pub.iaea.org/mtcd/publications/ pdf/te_1363_web.pdf, 2003, page 97 (accessed June 28, 2023).

17. Jackisch, R. Drone-based surveys of mineral deposits. Nat Rev Earth Environ 1, 187 (2020). https://doi.org/10.1038/s43017-020-0042-1

The growing attention towards New Energy has underscored the significance of geoscience in areas such as geothermal resources, carbon sequestration, and exploration for lithium and helium. Deep reservoirs, like the Basal Cambrian, have gained prominence, sparking discussions about shared pore space for different geotechnical applications. To foster dialogue within the geo-community, CEGA is delighted to host the second Energy and Emerging Technology in Geoscience (EETiG) Symposium in February 2024, along with the title sponsor SLB. The EETiG 2024 Symposium will span two days and bring together representatives from the carbon capture and sequestration, geothermal, lithium, and helium industries. The central theme will revolve around exploring shared pore space from a holistic perspective. The event aims to develop a geological understanding of these deep reservoirs, discuss the nature of shared aquifers, explore how mature oil & gas fields can support the development of these resources, and consider the roles of industry and government in fostering their advancement.

SESSION 1 – Going Deep…Again explores the frontiers of geoscientific research, emphasizing advancements regional mapping, addressing biases in existing datasets, and unlocking the potential of unexplored areas beyond traditional oil and gas fields. The regional geology and key aspects of the Basal Cambrian sandstone will be examined in the light of New Energy pathways. This session will also include lithium and helium exploration case studies looking on working with limited old data and understanding what new data needs to be collected for reducing uncertainty.

SESSION 2 – Shared Aquifer delves into the complex interplay between various industries reliant on shared aquifer systems. This session investigates the opportunities and potential conflicts of different New Energy activities within the same pore network. Bill Whitelaw will provide an industry overview on the shared pore space issue. Legal issues arising from different activities and different regulations will be discussed by Nick Ettinger. Case studies will be shared of where multiple New Energy projects are providing opportunities for the companies involved.

SESSION 3 – New Energy in Mature Oil & Gas Fields: asks the question on how to rejuvenate mature and depleted hydrocarbon fields in the

New Energy space. The AER will share learnings on induced seismicity.

Case studies involving CO2 as an Enhanced Oil Recovery (EOR) method and lithium from oil and gas produced waters will be shared. A panel discussion will explore the co-existence and opportunities of oil and gas operations in regions that New Energy activity is taking place.

SESSION 4 – Role of Government and Industry to Invigorate examines how collaborative research and innovation, effective industrial policy, and an appropriate regulatory/policy regime governing resource development can spur development and opportunities in New Energy. We will hear a geothermal case study on getting a project up and running. Innovate Calgary will also share how partnerships in research and development can help invigorate New Energy pathways.

We invite you to join us on February 7-8, 2024, for engaging technical sessions and collaborative dialogue as we embark on Adventures in Pore Space. Together, we can unlock the potential of New Energy and pave the way for a sustainable and innovative future. Registration opens November 2023. Technical program and details can be found on www.EETiG.ca.

Conference Co-Chairs: Matt Caddel and Darcy Reynolds

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SAMPLING MICROBES FROM DRILLING RIGS R.P.W. Stancliffe and L.M. Gieg

INTRODUCTION In the past it became commonplace for researchers to ponder what is living in deep sediments and petroleum reservoirs. Drilling rigs commonly produce wellbores many kilometres in length and recover chips and core for analysis by well site geologists and geoscientists in central labs. However, finding out what bacteria, archaea, fungi and viruses (collectively known as the ‘microbiome’) are present in the sediment has only recently become quick and inexpensive to do. This article aims to broadly outline what and how to sample for these microbes and highlight some of the common pitfalls. As with other sampling technologies in sedimentology and geochemistry; a ‘clean’ dataset needs to be constructed before changes to the microbiome can be used in drilling, completions, and production optimisation. Understanding a reservoir’s microbiome not only allows for an improved understanding of the subsurface environment, but can also help to pre-emptively address potential problems related to souring or microbial corrosion or optimise EOR or other improved production strategies.

BACKGROUND

WHY SAMPLE THE MICROBIOME?

Microbes are microscopic organisms, and when alive, can multiply quickly under the right environmental conditions. They are well adapted to the sediment conditions at depth and thus may not survive being brought to the surface. Changes in temperature, EH/pH, sunlight, contaminant biota and salinity are major causes of microbe mortality or microbiome change.

Changes in oxygen, methane, and/or hydrogen sulphide concentrations can also alter the composition of the microbiome.

As mentioned, microbes are well known to live under many different conditions, including in the deep subsurface and in many production fluids, and their presence and activity can be beneficial or detrimental to any oil field operation or process. Thus, knowing the microbiome of sediments encountered in a well can have many benefits to operators which include:

The microbiome composition (i.e., the types of microbes present) is also known to vary in different sediments, fluid chemistries, and temperatures.

This makes the sampling of each change in subsurface properties (i.e., each lithology) important in creating a microbiome model. Sediments that contain active microbes will be in the temperature range of zero to 90°C (though extremophiles can exist at higher and lower temperatures).

Above 90°C, microbes are generally killed, though over geological time they can re-enter the formation when it is back in the habitable range (< 90°C). Water migration, both from depth and the surface may also alter the microbiome especially if the water has a different salinity and contains nutrients and/or microbial spores.

• Effects of enhanced oil recovery (EOR) activity on production

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• The susceptibility of souring • Corrosion possibilities • Reduction in cementing containment • Microbial enhanced oil recovery (MEOR) optimisation • Size of ground water aquifer determination • Location of oil production from a vertical succession • Ability to successfully store hydrogen in underground chambers • The sealing capability of carbon capture utilization and storage (CCUS) caprock intervals

FIGURE 1

A typical mud tank on a rig. The tank is open and not sterile! (Courtesy of Chinook Drilling)

SAMPLING PROTOCOLS For the first time sampling of a hydrocarbon field, it is necessary to model the microbiome at all stages of the drilling process, i.e. from before spud to completion. Many microbiology-based studies have shown that improper sample collection and sample handling will give erroneous results about the microbiome,(1) so it is critical to ensure that new or sterile sample collection supplies are used throughout the sampling process.

• Fill container to the brim to reduce air retention and then close tight.

However, if the sample is to be frozen then a 15% expansion gap should be left.

More specific considerations include:

• Some duplicate samples can have a microbial preservative added to test its efficacy. Some recent studies have shown that preserving oil field samples with preservatives effectively captures the correct microbiome in a sample.(2, 3)

• Obtaining ample numbers of sterile or new sample bottles with airtight screw tops, at least 250 mL size; NalgeneTM and glass will both work.

• Background sample the mud tank, added water, every time a drilling additive is mixed into the mud, and pipe dope. This should be done because each additive can contain its own microbiome.

• Sample every time a new lithology is drilled. Collect fresh drill cuttings, mud, water, and any oil present.

• Sample wrapping in tinfoil or plastic wrap is not needed.

• Label with time and date of collection, drill depth, lithology interpretation, reason for sample and storage method.

• Keep some at fridge temperature and freeze others at -20 °C.

• Send the samples as quickly as possible to a lab for processing. The longer the wait, the more likely changes in the microbiome will occur. Microbiome analysis can readily be done be using DNA-based approaches, often referred to as molecular microbiological methods (MMM).(1) • Collect all the drilling logs, chip logs and Tour sheets. The lag time for the chips coming to surface is also important to know.

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• At the lab, the samples can be cleaned with distilled sterile water.

• The caved chips from the sample should be removed where possible and fluids processed separately to the chips.

• Do not dry the sample – air drying may add contaminants whilst heating can destroying the DNA present.

Once the detailed background model of all the microbiomes is made, a more selective sampling protocol can be adopted.

With recent technological advances, it is now possible to process some samples in the wellsite shack. This is only recommended once the microbiome model for the area is well understood.

SAMPLING CORE: A SPECIAL CASE FIGURE 2

The shale shaker is the best place to collect mud samples. Here there is dark bitumen and oil mixed in with rock chips and lighter drilling mud. These should all be sampled for microbiome analysis. (Courtesy of Chinook Drilling)

Cores are often cut from just above the zone of interest to just below its base. This makes understanding a change in the microbiome composition easy to determine.

If possible, the core should be cut into aluminium barrels, though PVC can be used.

The latter material may cause changes to the microbiome over time through degassing.

Cores should be collected at surface and quickly sealed before storing frozen or in a fridge.

The longer the core, the lower the chance of surface contamination.

A hole with a vapour lock should be drilled into each core barrel to allow gas to escape.

This gas composition should be sampled.

Core sampling is destructive so the Alberta Energy Regulator (AER) needs to approve that this can take place.

Preferably, the core barrels need to be X-rayed prior to sampling to place the core on depth.

Sample ‘pucks’ can then be cut from the core barrel along with samples taken from the barrel ends.

Sterile implements and containers should be used at all times when sampling for microbiome analysis.

FIGURE 3

A set of core barrels obtained from one well. The cores barrels have been cut into 2-meter intervals though the rock may not completely fill the tube. Detailed labelling is very important to preserve the order of drilling. (Courtesy of Chinook Drilling)

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Special attention should be paid to sample porous zones, oil/water/gas contacts, and lithology changes.

FIGURE 4

A chart of microbes living in a formation. These microbiomes were obtained from cores cut into the McMurray Formation.

After Ridley and Voordouw, 2018. (4)

RESULTS

REFERENCES/FURTHER READING

The samples can now be processed to find out the microbiome knowing that contamination has been reduced and that a detailed repeatable model can be created.

1. Rachel N.M., Gieg L.M. 2022. Microbiological Sampling and Preservation for Evaluating Microbial Communities in Oilfields and Other Biological Samples Using Molecular Microbiological Methods.

In: Failure Analysis of MIC. Eckert R.B., Skovhus TL (Eds.), Taylor & Francis (CRC Press).

The ultimate aim of the sampling is to create a database of DNA (and thus microbes) living in the sediments. This could be very detailed to begin with, but later drilling and sampling can look for changes rather than the total microbiome. This reduces the number and hence cost of sampling and speeds up interpretation significantly.

2. Rachel N.M., Gieg L.M. 2020. Preserving microbial community integrity in oilfield produced water. Frontiers in Microbiology 11: 581387, https://doi.org/10.3389/fmicb.2020.581387 3. Sharma M., Taylor N., Gieg L.M., Place T., Shen Y., Nicoletti D., Sargent J. 2022. Impact of preservation method, storage temperature, and processing time on microbiological community shift in solid samples collected from crude oil transmission pipelines. Association for Materials Protection and Performance (AMPP). Paper #2022-18009.

4. Ridley C.M., Voordouw G. 2018. Aerobic microbial taxa dominate deep subsurface cores from the Alberta oil sands. FEMS Microbiology Ecology 94: 6, https://doi.org/10.1093/femsec/fiy073

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2023 UPCOMING EVENTS INFORMATION

NOVEMBER November 7th

Online + In Person

Tuesday | 12:00-1:00pm MST

Canadian Well Logging Technical Division Shale Volume Transformers: Clay Volume in Disguise Speaker: Jeff Dickson, Suncor Location: C EGA Conference Room, +15 level, 540-5 Ave SW, Calgary AB

Friday | 7:30-8:30pm MST

Paleontology Technical Division More than Monsters: Mesozoic Marine Reptiles Speaker: Dr. Hallie Street, MacEwan University Location: 4 825 Mt Royal Gate SW, Mount Royal University, Room B108

November 23rd

November 8th Wednesday| 12:00-1:00pm MST

International Technical Division Early Stage of a New Energy Super Cycle Speaker: Josef I. Schachter Location: C EGA Conference Room, +15 level, 540-5 Ave SW, Calgary AB

November 16th

November 17th

Online + In Person

Thursday| 12:00-1:00pm MST

Structural Geology Technical Division The Geometry of Hydrocarbon Fields in Fold and Thrust Belts, with Analogues from the Western Canadian Cordillera Speaker: Andy Newson, Folded Thrust Geology Ltd Location: C EGA Conference Room, +15 level, 540-5 Ave SW, Calgary AB

Thursday | 12:00-1:00pm MST

November 29th

GeoWomen

Wednesday| 11:30-1:00pm MST

Nuts and Bolts of an Energy TransitionHow the Future Might Look Speaker: M aggie Hanna, BSc., PGeo. | Fellow at Energy Futures Lab | Associate at CESAR (Canadian Energy Systems Analysis Research) | President, Innovation and Technology Scout at Common Ground Energy Location: C EGA Conference Room, +15 level, 540-5 Ave SW, Calgary AB

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Technical Luncheon The Carbonates’ Comeback Tour Speaker: Dave Hills Location: C algary Petroleum Club, Devonian Room 319 5 Ave SW, Calgary, AB T2P 0L5

2023 UPCOMING EVENTS INFORMATION

DECEMBER December 5th

VISIT UPCOMING EVENTS

Tuesday| 12:00-1:00pm MST

BASS Technical Division Spatial and Temporal Evolution of Matrix-rich and Associated Matrix-poor Sandstones in Deep-marine Slope and Basin-floor Deposits Speaker: J ag Ningthoujam, PhD. Canadian Natural Resources Limited Location: C EGA Conference Room, +15 level, 540-5 Ave SW, Calgary AB

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2023 Field Trip Season in Review Rachelle Pinnow

The CEGA field trip season was kicked off in May with a trip to Jura Creek near Exshaw, Alberta. The trip leader was Dr. Pavel Kabanov of the Geological Survey of Canada, looking at the drowning unconformity and anoxic sediments at the Devonian-Carboniferous boundary. Rated as an easy, half-day hike, the participants explored the Upper Devonian benthic platform carbonates of the Palliser Formation, overlain abruptly by the black pyritiferous shale of the Exshaw Formation, one of the major source rocks in Alberta’s subsurface. By all accounts, it was an informative, fun, and interactive day.

This year, the Field Trip committee launched a new series called Go Take a Hike…Together! These hikes are free for our members and are a wonderful way to get out and connect with our vast geo-community.

It is important to emphasize that the leaders of this series are all volunteers and are providing a valuable service to our membership.

The inaugural hike was on a beautiful day in June, consisting of a casual loop through Nosehill Park in Calgary’s northwest to view some noteworthy glacial erratics. Trip leader, Astrid Arts, toured the group around to some of the major erratics belonging to the Cambrian Gog Formation, part of the boulder train that originated in the Mount Edith Cavell area in Jasper National Park.

Also in June, Tako Koning lead a Go Take a Walk…Together studying 450-million-year-old Ordovician fossils around the inner city of Calgary. The field trip provided attendees with insight into the sedimentary history, paleoecology and organisms that existed in a shallow tropical sea 450 mya. The Tyndall Stone viewed on the tour is all from the Garson Quarry located near the town of Tyndall about 30 km northeast of Winnipeg, Manitoba.

In August, Astrid Arts and Mark Mallamo lead a trip up to the Helen Lake stromatolite beds in Banff National Park. Helen Lake is nestled in lovely alpine meadows enroute to Dolomite Pass. Many people have likely hiked to Helen Lake or Cirque Peak and not been aware of the gorgeous 3-D stromatolite outcrops that are reached by continuing along the trail past Helen Lake and climbing up the unnamed ridge above the lake. The domal stromatolites can be seen in cross section

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and plan view over an area that stretches close to a kilometre. Participants were also treated to some remarkable displays of bioturbation and syneresis cracks, which spurred much conversation. The weather in the morning was cool and foggy, but it turned sunny by early afternoon and ended up being a perfect day of hiking.

Our last field trip of the season was in September to see the K/Pg Mass Extinction Boundary on Knudsen’s Farm near Huxley, Alberta. The trip leader was Tako Koning, who arranged special permission with the landowners Kent and Marion Knudsen to access the outcrop, which is on the south side of the Red Deer River valley, south of Dry Island Buffalo Jump Provincial Park. Extensive geological, geophysical, paleontological, and geochemical data indicates that an asteroid with a 12 km diameter struck the Yucatan Peninsula in Mexico, resulting in a 200 km wide crater named Chicxulub. This asteroid strike has been dated to 66.5 million years ago and caused a mass extinction, the effects seen worldwide, including in Central Alberta. The hike to the K/Pg Boundary did not disappoint!

This season, all the hikes had excellent participant turnout, and some were at maximum capacity. Through positive feedback, trip leaders will continue to update future trips to accommodate participant interests. The Field Trip Committee is currently working on the lineup for the 2024 season. We are open to suggestions from our members and are always looking for more volunteers. Please click the link if you would like to submit a suggestion for our Go Take a Hike…Together series.

SUBMIT HERE The CEGA Field Trip program provides opportunities for members to gain field experience, including GeoTours to international locations, the free series Go Take a Hike…Together, and guided trips to geological points of interest in Alberta and British Columbia. There was plenty of opportunity to get outside this season, connect with your geo-community, and see some great outcrop. We hope to see you on our 2024 field trips!

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From the Desk of the AER Nevenka Nakevska, Arif Rabbani, Alex Onojeghuo, Hugo Geng, Matt Grobe, and Dan Palombi

QUANTIFYING ALBERTA’S GEOTHERMAL RESOURCES: Developing a Geothermal Atlas of Alberta Introduction Geothermal energy is harnessed from the Earth’s natural heat reservoirs and offers a clean energy alternative that can be abundant in sedimentary basins. The Alberta portion of the Western Canada Sedimentary Basin (WCSB) contains numerous sedimentary intervals with high temperature and aquifer characteristics creating favourable conditions for the existence of geothermal resources.

Recently, academic and government researchers as well as industry have been actively exploring Alberta’s geothermal energy potential as a complement to our traditional hydrocarbon-based energy sector.

They recognize the advantage of utilizing established infrastructure and wealth of data and information collected from hydrocarbon exploration and development. The Alberta Energy Regulator (AER) and Alberta Geological Survey (AGS) fulfill their respective roles in the responsible development of geothermal resources by establishing the regulatory regime, providing the geoscience for evaluating emerging resources, and conducting energy resource appraisals.

Geothermal Research and Government Initiatives Knowledge of the geothermal regime in the WCSB has been established through the exploration and development of hydrocarbon and mineral resources. The generation

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of different types of hydrocarbons and metallic mineral deposits is dependent on the temperature reached during their genesis (Bachu and Burwash, 1994). Alberta’s geothermal resources are found in some of the same geological formations that have been explored for hydrocarbon resources.

Geothermal research in the Alberta Basin commenced in 1962 when the first heat flow measurements were done in two wells near Edmonton (Garland and Lennox, 1962).

Between 1976 and 1986, as a proactive response to an unexpected increase in the oil price and the general perception of depleting hydrocarbon resources, the Government of Canada initiated the Geothermal Energy Program. During this time, existing geological data from hydrocarbon exploration were gathered and analyzed to identify geothermal resources in Canada (Jessop, 2008). Targeted geothermal studies and exploration were completed, such as drilling to investigate the geothermal potential around Regina and Moose Jaw. There are numerous regional

studies on the geothermal potential of the WCSB. Many of them contain a review of early geothermal work in Canada (e.g., Majorowicz and Jessop, 1981; Majorowicz and Grasby, 2010). Researchers often revise the earlier studies with improved methodologies, and temperature and geological data for areas of interest (e.g., Walsh and Grasby, 2013; Weides and Majorowicz, 2014; Banks and Harris, 2018). However, formation-scale favourability mapping of Alberta’s primary aquifers for geothermal utilization has not been undertaken.

Using Geoscience for Regulation and Informed Decision-Making Recognizing the importance of the development of geothermal energy in the province, the Government of Alberta proclaimed the Geothermal Resource Development Act (GRDA) in December 2021 (Government of Alberta, 2021). This Act

FIGURE 1

Example geothermal favourability mapping of the Leduc Formation in west-central Alberta using spatial analysis and a GIS multicriteria approach. The spatial data layers on the left show temperature, porosity, and aquifer indication of which inform the resultant geothermal favourability map on the right.

establishes a regulatory regime administered by the AER for the responsible development of geothermal resources below the base of groundwater protection. The AER designed the regulatory pathway by developing the Geothermal Resource Development Rules and Directive 089: Geothermal Resource Development (Alberta Energy Regulator, 2022a, b). These instruments cover the entire life cycle of geothermal development for wells, facilities, and pipelines from initiation, construction, operation, and closure, and provide requirements for authorizations, liability management, well conversion, and risk management.

The role of the AGS, a branch of the AER, is to provide geoscience data, information, and advice on Alberta’s resources including geothermal. During the last 3 years, the AGS

has been undertaking significant work to characterize and quantify Alberta’s geothermal potential with the objective to develop a Geothermal Atlas of Alberta. The AGS is producing new geothermal favourability maps based on updated subsurface temperature data, prospective aquifers, and models of porosity and thickness using wireline logs and stratigraphic picks. Moreover, the AGS is conducting volumetric heat-in-place and power generation capacity assessments of favourable target units.

Years of effort to quantify geothermal resources will be available to the public through an online interactive GIS application named the “Geothermal Atlas of Alberta”.

This platform will serve as a comprehensive repository for all geothermal-related work conducted by AGS in recent years, promoting

access to data, information, and knowledge and enabling informed decisions in the pursuit of sustainable energy solutions.

The AGS Geothermal Resource Characterization Project Our objective is to characterize geothermal resources using various methods and techniques to develop resource assessments for the province. This work will support the government and geothermal industry, encourage exploration, and provide a basis for evaluating the economics of geothermal energy use. The three main components of the project are: 1) geothermal favourability mapping, 2) quantification of geothermal resources, and 3) developing a geothermal atlas.

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FIGURE 2

Example of geothermal resource calculations for the Leduc Formation within west-central Alberta.

Geothermal Favourability Mapping To improve the characterization and quantification of geothermal resources, the AGS is developing a practical method for identifying, screening, and characterizing potential geothermal reservoirs. Distinct from other favourability studies in Alberta, our work evaluates core analyses, well logs, and drillstem tests, to identify the presence of suitable aquifers in addition to the geothermal regime. The evaluation is formation scale and narrows down to specific areas where favourable geological conditions for geothermal resources are predicted to exist.

Following the methodology used by PalmerWilson et al. (2018), we have developed an integrated data-driven mapping approach to identify favourable geothermal areas within specific formations. The approach involves applying a GIS overlay analysis of criteria important for geothermal systems. Regional

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temperature data (Brinsky et al., 2022) were combined with petrophysical, geological and hydrogeological data to create three spatial data layers: temperature, porosity, and aquifer indication (Figure 1). Next, each layer was reclassified and favourability scores were assigned to parameter values. Finally, weights to classify the relative importance of each spatial data layer were defined and sensitivity analysis was performed. Formation-scale favourability maps have been calculated for the Leduc, Swan Hills / Slave Point, Granite Wash, and Gilwood geological units showing regions with four geothermal favourability classes from low to very high. These formationscale geothermal favourability maps are the province’s first, developed using a systematic knowledge-based GIS multi-criteria approach.

Quantification of Geothermal Resources

After identifying favourable geothermal areas, we estimate the total thermal energy or heat in place of key aquifers in the basin using the USGS volumetric method (Williams et al., 2008; Garg et al., 2010; Palmer-Wilson et al., 2018).

The method includes reservoir properties such as temperature, reservoir volume, rock and fluid properties (i.e., porosity, specific heat capacity, and density). With this conventional resource estimation method, we employ Monte Carlo simulations, a stochastic sampling approach, to capture the uncertainties in the input parameter estimations giving a range of values for the previously mentioned grids and their associated probabilities. Additionally, we use a well-based approach to capture the reservoir’s petrophysical changes, such as the presence of different mineralogy to determine more appropriate specific heat capacity of rocks. The stochastic and wellbased techniques are used to validate the resource quantification estimates.

The favourability mapping plays a vital role in further quantifying geothermal resources.

From the heat-in-place estimates, we calculate the gross thermal and electrical power

potential using methods described in Palmer-Wilson et al. (2018) and Banks and Harris (2018). The gross thermal power potential (MWth) is derived from exergy, which is the amount of energy available to perform useful thermodynamic work. Electrical utilization efficiency accounts for losses in the heat to electricity conversion and power plant operation to calculate the gross power capacity (MWe). The required brine flow rate to generate the predicted gross power capacity is obtained from the recoverable thermal energy and changes in brine enthalpy at the reservoir and ambient temperature.

Figure 2 shows a selected polygon in the geothermal favourability map of the Leduc Formation and the power generation capacity calculations.

Within the 1.45 km2 area, the median temperature is 147 °C, and the depth to the top of the formation is 4492 m. This area within the Leduc Formation stores 111.05 to 117.39 ± 4.37 PJ of heat in place as derived from the well-based and stochastic volumetric approaches. The heat recovery factor for the sedimentary basin ranges from 5% to 15% (Banks and Harris, 2018; Palmer-Wilson et al., 2018). At 10% recovery, the mean amount of thermal energy at the wellhead from the stochastic approach is 11.74 ± 0.44 PJ. With 30% electrical utilization efficiency (based on the temperature), the gross electrical power is 1.29 ± 0.26 MWe. The corresponding gross electrical power capacity per unit reservoir volume is 3.98 ± 0.81 MWe/km3 and would require 67.95 ± 19.42 m3/hr/MWe brine flow rate as derived from the stochastic method. The well-based method provides 3.50 MWe/km3 at 78.10 m3/hr/MWe flow rate.

Geothermal Atlas of Alberta The Geothermal Atlas of Alberta is a web-based GIS application which will provide relevant geoscience data and information for the characterization and quantification of Alberta’s geothermal resources.

The Atlas is intended to support the government and regulator, the public, and industries in the exploration and sustainable development of geothermal energy in Alberta. The Geothermal Atlas will include maps of favourable geothermal areas, temperature distribution and thermal gradient maps, formation water chemistry, and the estimation of the heat-in-place and electrical power generation capacity for select stratigraphic intervals. This work provides a foundation for making geoscience-informed decisions to evaluate suitable locations for geothermal development.

Highlights The AGS has produced the province’s first formation-scale geothermal favourability maps using a systematic knowledge-based GIS multi-criteria approach. Our approach uses geological and petrophysical criteria and the temperature gradient to identify favourable conditions for geothermal resources. To further quantify geothermal resources, we estimate heat-in-place and calculate the gross thermal and electrical power potential using the USGS volumetric method combined with a well-based approach that uses input variables derived from well logs. Our long-term goal is to apply the methodology for geothermal favourability mapping to other target formations and subsequently host the results in our Geothermal Atlas of Alberta.

References Alberta Energy Regulator, 2022a. Directive 089: Geothermal Resource Development Act, Bulletin 2022-25.

Alberta Energy Regulator, 2022b. Geothermal Resource Development Rules. URL https://kings-printer.alberta.ca/570. cfm?frm_isbn=9780779843817&search_by=link.

Bachu, S. and Burwash, R., 1994. Geothermal regime in the Western Canada sedimentary basin. In Geological Atlas of the Western Canada Sedimentary Basin. Edited by G. Mossop and I. Shetsen. Canadian Society of Petroleum Geologists and Alberta Research Council, Special Report 4, 447 –454.

Banks, J. and Harris, N.B., 2018. Geothermal potential of Foreland Basins: A case study from the Western Canadian Sedimentary Basin. Geothermics 76, 74–92.

Brinsky, J., Singh, A., Hauck, T.E., Grobe, M., and Palombi, D., 2022. Temperature mapping of select Devonian strata in Alberta. Alberta Energy Regulator / Alberta Geological Survey, AER/AGS Open File Report 2021-05, 28 p.

Garg, S.K. and Combs, J., 2010. Appropriate use of USGS volumetric “Heat in Place” method and Monte Carlo Calculations. In Proceedings 34th Workshop on Geothermal Reservoir Engineering. Stanford University, Stanford, CA, 7 p.

Garland, G. and Lennox, D., 1962. Heat flow in western Canada. Geophysics 6, 245–262.

Government of Alberta, 2021. Geothermal Resource Development Act. Statutes of Alberta, 2020, Chapter G-5.5.

Jessop, A.M., 2008. Review of National Geothermal Energy Program Phase 1 – Geothermal Potential of Sedimentary Basins. Geological Survey of Canada, Open File Report 5690.

Majorowicz, J.A. and Grasby, S.E., 2010. High potential regions for enhanced geothermal systems in Canada. Natural Resources Research 19, 177–188.Majorowicz, J.A. and Jessop, A.M., 1981. Regional heat flow patterns in the western Canadian sedimentary basin. Tectonophysics 74, 209 –238.

Palmer-Wilson, K., Banks, J., Walsh, W., and Robertson, B., 2018. Sedimentary basin geothermal favourability mapping and power generation assessments. Renewable Energy, 127, 1087 –1100.

Walsh W. and Grasby S. E., 2013. Geothermal resource assessment of the Clarke Lake gas field, Fort Nelson, British Columbia. Bull. Can. Petrol. Geol. 61, 241–251.

Weides S., and Majorowicz, J. A, 2014. Implications of spatial variability in heat flow for geothermal resource evaluation in large foreland basins: the case of the Western Canada Sedimentary Basin. Energies 7, 2573– 2594.

Williams, C.F., Reed, M.J., and Mariner, R.H., 2008. A review of methods applied by the US Geological Survey in the assessment of identified geothermal resources. US Geological Survey Open-File Report 2008-1296, 27 p.

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GEOLOGY IN MOTION

THE GEOLOGY OF THE BATTLE OF VIMY RIDGE Dallin Laycock, Sean Fletcher, Erin Pemberton, Paul Bremner, Richard Mackenzie

INTRODUCTION: Every November 11th we commemorate Remembrance Day, which provides a solemn moment to unite in honoring the tremendous sacrifices of our fallen soldiers, including the 3,598 Canadians killed in the Battle of Vimy Ridge, which took place from April 9 to April 12, 1917, during the First World War (WWI). Located in northern France, Vimy Ridge was a formidable stretch of high ground that had been under German control since 1914. Its strategic importance lay in its commanding view of the surrounding landscape, which made it a natural fortress for those who held it. This battle was a part of the broader British-led Arras Offensive, which aimed to break through the formidable German defensive lines in the region (Figure 1). For the first time all four Canadian divisions attacked together: soldiers from all regions of Canada were present at the battle.

Brigadier-General A.E. Ross declared after the war, “in those few minutes I witnessed the birth of a nation.” The Battle of Vimy Ridge would go on to become one of Canada’s most celebrated military victories (Foot, 2006).

FIGURE 1: Geological map of the area surrounding the Vimy Ridge. The red dashed line shows the location of the Western Front in 1917. Vimy Ridge is shown with a red star. Geologic map sourced from infoterre.brgm.fr.

The significance of Vimy Ridge extended beyond its military fortifications.

Previous attempts by French and British forces to capture it had resulted in heavy casualties and ultimate failure (Gendzwill, 2007). The ridge symbolized the deadlock of trench warfare on the Western Front, with fortified positions and intricate defensive networks, making any advance a perilous endeavor. It was under these circumstances that the Canadian Corps, under the leadership of General Julian Byng and General Arthur

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Currie, launched their meticulously planned and innovative assault on Vimy Ridge. This battle ultimately proved to be a turning point in World War I, showcasing the potential for victory in an otherwise brutal and stagnant conflict. This article examines the crucial role that geology played in the battle, from the presence of the ridge itself, to the preparations, execution, and even the battle’s ultimate memorialization.

FIGURE 2: Original cross section from T.W. Edgeworth David, made during preparations for the battle. The black dotted box shows the approximate interval described in Figure 3. Modified from nla.gov.au.

GEOLOGIC BACKGROUND: The Western Front of WWI was largely static in 1917 (Figure 1). WWI saw a dramatic increase in the accuracy and efficiency of artillery and machine gun fire, which reduced the effectiveness of offensive frontal assaults by infantry (Doyle, 2014). In response, both sides placed increased emphasis on defensive positions. The topography of the land then became extremely significant to the outcome of the war, as the high ground controlled the efficacy of defensive positions.

Some authors have argued that the Western Front of WWI was essentially a war fought over topographic positions (Doyle, 2014).

As a result, geology became a key strategic component of the war. Everything from river morphologies, structural features, and substrate composition needed to be factored into battle plans. The impact of geology became especially apparent when considering subsurface conditions during military mining operations.

Each of the opponents recognized the importance of geoscience to the operation and so appointed geological staff and advisors. The Germans had the initial advantage, having gained ground early in the conflict, and had set up defensive positions in high ground wherever possible. They set up a large geological staff, and even found extensive geological information within the occupied city of Lille (Doyle, 2014). The Allies appointed Major (later Lieutenant Colonel) T.W. Edgeworth David to focus on military mining and dugout construction,

FIGURE 3: Stratigraphic chart showing the original informal stratigraphic divisions from T.W. Edgeworth David on the right, shown in italics. This is shown adjacent to our interpreted connection to the modern stratigraphic column of the area. Also illustrated are the dominant fracture patterns within the Lewes Nodular Chalk Formation and the Seaford Chalk Formation. Grey boxes show the relative stratigraphic position of common excavations.

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FIGURE 4: Plan of attack for Vimy Ridge that shows the topography of the ridge, which was an important part of the battle plan. Large arrows added for emphasis. Of note is the area referred to as “The Pimple”, which is visible to the north of the area assigned to the 4th Division (small purple arrow). The Pimple was the final part of Vimy Ridge to be captured by the Allies. Image credit: Drawn by the Dominion Bureau of Statistics, printed by Geographical Section, General Staff, Department of National Defence - Library and Archives Canada does not allow free use of its copyrighted works. See Category:Images from Library and Archives Canada., Public Domain, https://commons.wikimedia.org/w/index. php?curid=4174127.

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and Lieutenant (later Captain) W.B.R. King to focus on water supply (Doyle, 2014). T.W. Edgeworth David constructed the geologic cross section of Vimy Ridge, shown in Figure 2. Modern stratigraphic divisions have since been created for this area, and our interpreted correlation and reconciliation with modern stratigraphy is shown in Figure 3.

Geology of the Vimy Ridge area comprises a thin layer of weathered silt and clay overlying Cretaceous chalks. These chalks at Vimy Ridge are equivalent to the icon chalk cliffs found in Southern England, which are perhaps the most famous chalk deposits in the world. These were deposited in the Late Cretaceous epoch on a submerged continental shelf in water depths between 100-300 m (Tucker and Wright, 1990). In this region of France, the chalk reaches a thickness of approximately 200 m, and contains interbedded layers of clayrich marl, bioturbated nodular chalk, hardgrounds, and flint seams. These variations contribute to variable porosity, permeability, and geomechanical properties. At Vimy Ridge, the mining and excavations were located primarily within the Seaford Chalk and Lewes Chalk. While there was lots of internal variability within the chalks, they were collectively soft enough to allow for subterranean mining operations.

The Lewes and Seaford chalks are primarily comprised of coccoliths, with lesser amounts of planktonic foraminifera and calcispheres. Macrofossils common within the shallower facies include echinoids, sponges, bivalves, bryozoans, and brachiopods. Deeper-water chalk facies feature belemnites, ammonites, and crinoids as the most common macrofossils (Tucker and Wright, 1990).

Trace fossils are also common, with Thalassinoides, Chondrites, Zoophycos, and Planolites being the most commonly reported (White, 2007).

The topography at Vimy Ridge consists of gently folded Upper Cretaceous chalks disconformably overlain by Paleogene sediments. The Somme region is part of the larger Weald-Boulonnais anticlinorium that reaches all the way into southern England, creating regionally pervasive northwest-southeast trending structures (White, 2007). Vimy ridge itself is one of these structures, a ridge created by the Marqueffles fault. It’s a NW-SE trending normal fault, creating a 9 km long ridge with approximately 100m in elevation (Figure 4), with a smaller adjoining hill to the NW referred to as “The Pimple”. Characterizing the ridge itself was an important part of developing the battle plan. As such, highly dangerous aerial reconnaissance was even used to take photographs to better analyze the topography and exposed geological structures (Figure 5).

FIGURE 5: Aerial reconnaissance aircraft taking photographs of the topography below. The camera apparatus can be seen in black below his right hand. This photograph Q 33850 comes from the collections of the Imperial War Museums., Public Domain, https://commons.wikimedia.org/w/index.php?curid=632051.

INFLUENCE OF GEOLOGY ON MILITARY EXCAVATIONS: Geology was a major contributing factor to excavating and mining efforts throughout WWI. This was especially true at Vimy Ridge. As discussed, the relatively soft rock allowed for extensive excavating and tunneling on both sides. Allied excavations at Vimy Ridge included trenches, subways, dugouts, and fighting tunnels (Figure 6). The tunnels were constructed secretly, with a total of 11 subways, totalling approximately 6 km in length.

Many of these extended from the rear areas to deliver troops, artillery, and supplies to the battlefront ahead of “no man’s land” (Foot, 2006).

Subways were constructed at depths between 10 and 20 m below ground to target the most geomechanically favorable stratigraphy wherever possible. These needed around 16 m of rock overhead to protect troops against heavy artillery (Deiderichs and Hutchinson, 2020). To prevent roof collapse, the width of the tunnels were kept to a minimum, with average dimensions of 2 m in height and 1 m in width (Rosenbaum, 1989). Tunnel width was also planned in accordance with local fracture geometries, with lithological variation showing strong control over fracture geometry and orientation (White, 2007). For example, the white chalk of the Seaford Chalk Formation exhibited typical sub-vertical and sub-horizontal fracture networks, while the Lewes Nodular Chalk Formation featured characteristics such as conjugate fracture sets and slickensided fracture walls (illustrated in Figure 3). The majority of subways and major tunnels are located within the Lewes Chalk, and occasionally they are found within Seaford Chalk.

Deeper fighting tunnels, used to detonate explosives under forward enemy positions were also mostly located in the deeper Lewes Chalk (Figure 3, see also White, 2007).

The fracture patterns within the Seaford Chalk and Lewes Chalk have also played an important role in the long-term stability of

FIGURE 6: Image showing one of the Allies fighting tunnels near Vimy Ridge. Image credit: Labattblueboy - Own work, CC BY-SA 3.0, https://commons. wikimedia.org/w/index. php?curid=3871867

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the tunnels. The battle occurred more than 100 years ago, and over that century, weathering and dissolution has rendered most of the tunnels inaccessible. Fractures provide conduits for meteoric water dissolution, weakening tunnel walls and ceilings. Shelling during the battle itself created additional fractures and even collapsed some of the tunnels.

Even to this day, this creates a potential hazard at the surface for both tourists and surface infrastructure (Deiderichs and Hutchinson, 2020).

GEOPHYSICS AT VIMY RIDGE: It wasn’t just the Allies who were able to exploit the chalks to create tunnel systems. The Germans were also advancing underground toward the Allies, which was of great concern to Allied operational planning. The first geophones were invented for these purposes and would be placed against excavation walls to detect enemy movement (Rosenbaum, 1989). These listening devices could accurately detect German mining up to 100 m away (Boire, 1992).

One innovative soldier, Counter Battery Officer Andrew McNaughton, started to develop improved methods to identify key enemy targets using geophysical methods. He brought in additional scientists to assist in developing new sound ranging and flash spotting methods to triangulate enemy cannons and provide more accurate targets for counter-battery fire (Gendzwill, 2007).

THE BATTLE: Before dawn on April 9th, Easter Monday, 15,000 Canadian soldiers, the initial assault wave, gathered covertly in subways, shell holes, and trenches. The cold pre-dawn air and hardened muddy substrate were exacerbated by snow and sleet, concealing them from the enemy’s view.

At 5:30 a.m., Allied artillery thundered, commencing the assault. The Canadians advanced behind the relentless artillery barrage, shielded by 150 well-placed machine guns. By late afternoon on that same day, three of the Divisions achieved their objectives on schedule, and pushed back the German front nearly 5 Km. However, things were not as successful for the 4th Division. Just minutes into the assault, the 4th Division faced withering fire, suffering heavy casualties. Confusion reigned, and Hill 145 and the Pimple remained unclaimed by nightfall. The next day, aided by 4th Division reserves, renewed attacks secured Hill 145. Two days later, on April 12th, the Pimple fell after an intense battle in the snow. This marked an unmatched Allied advance on the Western Front, showcasing Canadian resilience and securing their historic victory at Vimy Ridge (see Foot, 2006 for more detail on the battle).

MEMORIALS: The Canadian National Vimy Memorial, located in France, honors Canadian Expeditionary Force members who perished during World War I and serves as a tribute to Canadian soldiers from the same conflict without known graves in France (Figure 7). Situated within a 100-hectare battlefield park, it stands at the heart of the terrain where the Canadian Corps launched their initial assault during the Battle of Vimy Ridge.

The construction of the memorial, designed by Walter Seymour Allward, spanned eleven years. King Edward VIII unveiled it on July 26, 1936, in the presence of French President Albert Lebrun and a crowd exceeding 50,000, including 6,200 attendees from Canada. Following a comprehensive multi-year restoration effort, Queen Elizabeth II re-consecrated the monument on April 9, 2007, during a ceremony marking the 90th anniversary of the battle.

Initially, Allward wanted to use white marble for the memorial’s exterior, but was advised against it, citing concerns about marble’s suitability for the northern French climate. Instead, Allward embarked on a two-year journey to locate stone that possessed the right color, texture, and resilience (Hucker, 2007). He discovered it amidst the ruins of Diocletian’s Palace in Split, Croatia, where he noted the stone’s enduring quality over time (Figure 7). His selection, the Cretaceous Seget Limestone, originated from an ancient Roman quarry near Seget, Croatia.

Another memorial is located in Waterton National Park, in Southern Alberta. A mountain previously referred to as Goat Mountain was renamed as Vimy Peak, to honour those who fought in the battle of Vimy Ridge. The geologic history of this mountain and the surrounding area can be divided into 3 main phases: 1) Deposition of the Belt-Purcell Supergroup, 2) Mountain Building, and 3) Glaciation and subsequent surficial processes. The Belt-Purcell Supergroup was deposited approximately 1.45 Ga, and despite its great age, has not been metamorphosed. The result is a colorful blend of reddish-brown to green mudstones, light grey limestones, and tan-grey dolomites. Stromatolites are commonly found within Waterton Park, albeit not commonly within the strata of Vimy Peak.

FIGURE 7: A) The Canadian National Vimy Memorial, located at the battleground in France. B) Diocletian’s Palace in Croatia, which uses the same Seget limestone as the National Vimy Monument.

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Vimy Peak consists of stacked thrust faults, resulting in thrust-repeated successions of Altyn Formation, Appekunny Formation, and Grinnell Formation (Figure 8). This deformation is the product of mountain building that started ~165 Ma (Mudge and Earhart, 1980), with the

FIGURE 8: A) Photograph of Vimy Peak as seen from the Prince of Wales Hotel near the Bear’s Hump trailhead. B) Annotated photo of Vimy Peak, showing approximate location of major thrusts in red, and unit boundaries in yellow (see Gordy et al., 1977).

Lewis Thrust being the major detachment surface under Vimy Peak. The strata of the Belt-Purcell Supergroup were carried to the northeast on the Lewis Thrust for approximately 140 km, before reaching their final location around 58 Ma. Pleistocene glaciation was then responsible for carving the mountains of Waterton into their current morphology. The resulting majestic beauty of this mountain serves as a reminder of the stalwart nature of the forces who fought in the battle of Vimy Ridge.

REFERENCES AND SUGGESTED READINGS: Cook, T. The Battle Of Vimy Ridge, 9-12 April 1917. https://www. warmuseum.ca/the-battle-of-vimy-ridge Deiderichs, M., Hutchinson, D.J. (2020). Tunnel Warfare in World War I: The Underground Battlefield Tunnels of Vimy Ridge, France. Published in Tunnels and Underground Cities: Engineering and Innovation Meet Archeology, Architecture and Art, Volume 1. p. 52-61.

Gendzwill. D. (2007). Vimy Ridge and Geophysics. CSEG Recorder, June 2007, Vol. 32 No. 6.

Hucker, J. (2007). The Meaning and Significance of the Vimy Monument.

In Hayes, Geoffrey; Iarocci, Andrew; Bechthold, Mike (eds.). Vimy Ridge: A Canadian Reassessment. Waterloo: Wilfrid Laurier University Press. pp. 279–290. ISBN 978-0-88920-508-6.

Hutchinson, D.J., Diederichs, M., Pehme, P., Sawyer, P., Robinson, P., Puxley, A., Robichaud, H. (2008). Geomechanics stability assessment of World War I military excavations at the Canadian National Vimy Memorial Site, France. International Journal of Rock Mechanics and Mining Sciences. Vol 45, No. 1, P. 59-77.

Rosenbaum, M.S. 1989. Geological Influence on Tunnelling Under the Western Front at Vimy Ridge. Proceedings of the Geologists’ Association. 100 (1). Pp. 135 – 140.

Doyle, P. (2014). Geology and the war on the Western Front, 1914–1918.

Geology Today. Vol. 30, No. 5. Pages 183-191.

Tucker, E.M. and Wright, V.P. 1990. Carbonate Sedimentology. Blackwell Scientific Publications., London, Great Britain.

Foot, R. (2006). Battle of Vimy Ridge. The Canadian Encyclopedia. www. thecanadianencyclopedia.ca

White, M.C. (2007). Geologic Controls on Instability in WWI Excavations, Canadian National Memorial Site, Cimy, France. Thesis. Queens University.

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