Unconventional vein system modelling to reduce exploration risk and enhance borehole targeting

amassing significant archive data that Cornish Lithium has digitised for lithium exploration. This presentation will explain how to import analogue data, digitise it using polylines and vein systems to create an accurate geological model, and show how this reduces risk and exploration costs while enhancing borehole targeting. We’ll compare a predictive pre-drilling model to a proven post-drilling model and explain how unassigned borehole data can be integrated using control points to update interpretations.

Overview

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<v ->Hi everyone. Welcome to my Lyceum 2021</v>

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technical presentation.

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Today I’m going to talk about

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how we’ve used Leapfrog Geothermal

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to reduce our exploration risk

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and enhance our borehole targeting

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using historical mining data and polylines

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to create vein systems.

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Some of the data you see today

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is covered by the following disclaimer,

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so please feel free to read this within your own time.

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So I’m Adam Matthews,

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I’m a project geologist at Cornish Lithium

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and my primary role is collating historic mining data

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to create exploration targets,

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and to plant boreholes into these exploration targets.

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The Cornish Lithium is split into

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the following four work streams.

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The one that we’re going to focus on today

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is the Shallow Lithium-enriched

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Geothermal Waters workstream.

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This is looking at lithium-enriched water,

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which circulates naturally along

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permeable geological faults.

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The deep geothermal waters

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is exactly the same geological concept.

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It’s just a fine natural break,

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because shallow boreholes around two kilometers depth

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cost about one million pounds to drill.

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And deep boreholes around five kilometers depth

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costs over 20 million pounds to drill.

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We also evaluate lithium in hard rock across Cornwall.

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This is looking at lithium-enriched micas

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hosted in the granites.

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And we also evaluate other metals such as tin and copper,

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because Cornwall was once

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prolific tin and copper mining district.

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So tin and copper is quite frequently found

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within historic mining archives

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and in the boreholes that we drill.

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So Cornish Lithiums was founded looking for

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lithium-enriched geothermal waters,

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and the company knew that there may be

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lithium-enriched geothermal waters

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due to the historical mining archives.

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So this is an example of that.

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It’s a cross-section through United Mines

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and it’s along a structure called hot lode,

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which was once a very rich copper structure,

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but it was recorded that hot waters were issued

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into that structure,

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and that these hot waters were rich in lithia,

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which is what we know today as lithium.

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So this kind of data is what we started

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to build this concept that we could intercept these waters

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and be able to produce lithium from them.

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The concept is that these geothermal waters

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upwell from depth along naturally permeable faults,

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they potentially could convect.

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And we can use the historic mining archives

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to locate where these may occur.

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We can also use them

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to create 3D geological models within leapfrog,

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and we can project

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the structure to depth

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really accurately from historic data,

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which we’ll show you today.

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And then we can drill and intercept

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these structures at depth,

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then be able to pump these fluids to surface

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for geochemical analysis.

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And hopefully in the future,

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we can produce lithium from them.

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So now let’s head into leapfrog.

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We’ll go through the geological modeling process.

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We’ll have a look at its accuracy,

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and then we’ll have a look at how we can integrate

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the new borehole data into the model as well.

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So I hope you’ll enjoy it.

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And if you have any questions at the end,

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please save them for the Q&A.

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So here you can see the cross-section

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I just showed you in the PowerPoint,

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but it’s been imported into leapfrog

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and positioned correctly in geographic space.

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When you import a cross-section into leapfrog,

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the following screen will appear

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and you can use three control points

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to position the cross-section correctly.

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For these old cross-sections,

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we usually use position of the shafts,

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but on newer cross-sections you could use local

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or national grids to georeference the cross-section.

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So there’s quite some historic data being

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almost 200 years old,

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still extremely valuable for Cornish Lithium.

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This is because it’s an accurate representation

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of where the structure has previously been mined.

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This type of data can also be found throughout the mine,

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and going to be collated into a series of cross-sections,

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which Cornish Lithium has spaced every 100 meters

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through the mine.

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Part of this collation process,

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is to make sure the best geological understanding

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of the area

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from all of the historic data available.

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And we add additional structures

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and provide comment on each of the cross-sections

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for our modeling.

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We generate geological models using a vein system.

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On the Digital Geological Models tab

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in your geological model,

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you can navigate surface chronology.

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right-click

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and press New Vein System.

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New vein system needs a lithology.

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This lithology could be anything that you’ve selected

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or you’ve created with part of the borehole

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in your Lithology tab

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underneath your geological modeling model.

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You can right-click Lithologies and you press Open.

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The vein lithology is the lithology

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of the entire vein system.

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So you can see in some situations

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I’ve created a new lithology

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called Consolidated Mines for example,

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and that’s because I’ve modeled entire vein system

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as a mine.

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In the situation we’ve got today,

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I’ve modeled this vein system

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as the hot middle south lode vein system.

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And that’s because this section of this mine,

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middle lode interacts with both the south lode and hot lode,

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by terminating against the hanging wall of south lode

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and the footwall of hot lodes.

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And a vein system is the best way

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to model these kind of interactions.

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So, to create a vein within a vein system,

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you right-click the vein system.

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Now go to new vein.

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You can see there’s multiple options.

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Typically you’d model from lithology,

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which is your intervals within your borehole data.

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However, as we don’t have any borehole data,

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we’re only modeling from historic data in this situation.

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We’re going to have to use polylines.

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Within the polylines you can see

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that you need hanging wall and footwall polyline.

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So when digitizing the hanging wall polyline,

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we follow just where the hanging wall

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on the hanging wall of the fault

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on each cross-section.

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And when digitizing the footwall polyline,

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we digitize the footwall

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of that fault.

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And this allows you to have variable width

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and to represent the width of each fault.

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One of the most important factors is ensuring

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that the red ribbon on each polyline

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points towards the center of the vein.

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The red ribbon is the internal volume of that vein.

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And without or if they were incorrect,

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then leapfrog’s interpolation will also be incorrect.

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So you to ensure that that red ribbon is on the inside.

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To create vein,

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we find the polylines new vein,

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and then we select the polylines we’ve just made.

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And then we can press Okay.

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Once interpolation is finished,

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you can check the structure

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to make sure it makes logical sense.

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If it doesn’t make logical sense

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then you can edit polylines that you’ve just made

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until you are happy with the structure.

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You can then continue making more structures

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for that vein system.

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Ones that I’ve made for this vein system

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is hot south and middle lode.

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South lode is on the footwall side of hot lode.

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And middle lode lies between the two structures

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and it interacts with both the footwall of hot lode

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and the hanging wall of south lode.

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We can see that terminates against each.

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This is easy to do with an advanced system,

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you right-click Vein System,

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press Open

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and then navigate to the Vein System tab.

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If we go to click on Middle Lode,

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we can see that it says

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interaction type terminates against hot lode on the footwall

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and against south lode on the hanging wall.

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We can see under the vein column,

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only two options are available.

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That’s because of the position of middle lode.

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is beneath hot and south lode

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If you use the arrows on the right

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to move the position of middle lode,

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we could see more options become available.

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Once you’re happy with the interactions

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that you’ve assigned,

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you click Okay.

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And then leapfrog will know

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how to terminate your structure.

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In this situation as well,

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we can see the middle lode

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it’s also terminated on the left side of the screen.

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This isn’t due to any of the interaction

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with hot or south lode,

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and it’s due to the boundary conditions of that structure.

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If we open the Middle Lode tab,

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we can see that more,

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more options available.

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We can click on the boundary,

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right-click and click Edit,

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and you can see that you customize the strike

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of the structure.

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The topography is always higher priority

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than what you’ve drawn on this boundary.

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And also the interactions also higher priority

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than what you’re drawing on this boundary.

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So what we can see

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is that the structure terminates

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against footwall of hot lode.

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It terminate again,

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terminates against topography.

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And it also terminates against the hanging wall

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of south lode.

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But on this side,

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there is no other terminations assigned.

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So then it will terminate against this boundary polyline

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that we’ve drawn.

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And it’s very easy to modify.

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As you can see by just changing the points

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or you can draw a new polyline.

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So the next thing to do once you’re happy with both

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the layout of the veins

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and the interactions,

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is to add any additional information that you need

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to plan your boreholes.

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Some of that information,

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for me is going to be some mine workings data.

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As you can see by the black lines,

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I’ve digitized previously some stopes along hot lode.

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So we can see the position of the stoping

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to ensure that we do not drill through any stopes.

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And the position of the mine water temperatures

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that I’ve digitized from historic mining records.

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The red data points

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are temperatures of a 51 degrees celsius,

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and the blue data points

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are temperatures around 20 degrees celsius.

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In the bottom right,

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we can see a filter available as well.

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And this is because this data has,

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is time-dependent data based on when it was recorded.

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See the data in the 1920s is relatively cool.

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And through time,

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the data gets deeper and warmer.

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This is as expected as the mine will be getting deeper

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and be interacting with deeper, warmer fluids.

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When planning the boreholes,

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this information is used

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ensure that boreholes are positioned

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as accurately as possible.

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We plan the boreholes under the Well Data tab

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and the Planned Wells tab.

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You can right-click Planned wells

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and plan a well as you usually would within leapfrog.

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Our planned wells can be seen here.

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They’re located beneath the position

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of geothermal water occurrences

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and beneath mine workings.

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You can see that they’re relatively steep

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and this is due to position

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of another mine towards north,

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as can be seen here.

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We wanted to ensure that we avoided these mine workings.

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This mine has also been modeled using the same process

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as shown today.

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And this can be seen

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by these vein systems shown.

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For simplicity,

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we’ll make sure that just hot lode is visible

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the rest of the presentation.

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During drilling,

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we added this daily survey

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and borehole log data to leapfrog

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to be able to monitor the wells trajectory.

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This is done by right-clicking Wells and Pending wells.

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And then we can add in the updated daily logs.

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Once the borehole was complete,

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the boreholes were very close to the trajectory

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of the planned wells.

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What was also very interesting,

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is that I previously saved a static copy

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of the geological model before drilling.

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And this allowed us to check the accuracy

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of modeling from historic data.

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If we navigate the hot lode,

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middle lode and south lode vein system,

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and bring in hot lode,

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we can see the original projected position of hot lode

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before adding any drilling data.

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Using a slicer,

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we can show a slicing through the borehole

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and then we can accurately measure the distance

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between the predicted position of hot lode seen in black

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and the actual position of hot lode seen

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in the borehole logs indicated

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by the red and white band-aid.

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Red is a position of veins.

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White is position of core loss.

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There’s a lot of core loss in this interval

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due to its permeability.

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We can see that it’s about 14 meters difference

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between the predicted position of the structure

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and the actual position of the structure.

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And this is extremely good for the modeling

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from historic data,

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but also our financial models,

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because we were able to intercept the structure

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on a date that we predicted

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that we’d intercept the structure.

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Once we had intercepted the structure,

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we could test it for a certain concentration.

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You can see by the position that these black bands,

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locations where it pumped geothermal waters

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from each structure.

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We can see that we pumped geothermal waters from hot lode,

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which was our primary target structure.

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And this is only possible due to the position

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of that historic data.

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We also continued drilling to depth,

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or we were able to intercept numerous other structures,

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which held lithium enriched geothermal waters.

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I now show you how to update the interpolation,

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the addition of this new borehole data.

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So typically in leapfrog,

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it automatically updates structures

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with the addition of new data.

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Because we’ve made the structures in polylines,

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this isn’t possible because leapfrog hasn’t made

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the connection that that structure

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is based on a particular interval

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within the borehole.

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When assigning intervals in leapfrog from borehole data,

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typically navigate Lithology tab.

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right-click and add a new column.

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And then a group lithology.

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What I’ve previously made is the interval table.

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Right-click and opening Tool table,

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we can see all of the borehole lithologies.

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We can use this tool here to select intervals

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and we can assign them to a particular lithology.

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You also create new lithologies

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such as hot lode

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which is what we’re going to use today.

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Once the interval table has been made,

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we can see that it’s been,

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is now displayed on the borehole.

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We can change how it’s displayed.

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So for example,

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the original lithology,

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and I would explain the intervals.

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And we can see in pink,

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that I’ve assigned this vein

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as hot lode.

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What leapfrog would normally do now

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is link that structure

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to all the other boreholes that you’ve previously drilled

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as hot lode.

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But because we haven’t made that connection in leapfrog yet

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that this structure is called hot lode,

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we need to do that manually.

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The way you do that

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is by going to points,

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right-click points

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and create new contact point.

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A list of all the different interval tables are available.

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We’re going to use the interval table

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as I’ve just shown you.

[00:16:41.900]
For using Tool table,

[00:16:43.610]
we can select the primary lithology as hot lode

[00:16:47.950]
and the contact with the,

[00:16:49.400]
the contacting lithologies are any lithologies

[00:16:52.040]
you want the interpolation to stop against.

[00:16:55.370]
Ignore lithologies are any lithologies

[00:16:57.433]
that you want interpolation to continue through.

[00:17:00.370]
So for example,

[00:17:01.320]
we know that the core loss is inside the structure.

[00:17:05.220]
So you want the interpolation to continue through it.

[00:17:07.800]
We also have other structures like dykes

[00:17:10.200]
and we know that the fault continues through the dykes

[00:17:12.530]
to make sure the interpolation passes through those.

[00:17:16.620]
We also know that we had to use a hanging wall

[00:17:18.740]
and a footwall polyline.

[00:17:20.490]
So you also need hanging wall and footwall contact points.

[00:17:24.340]
So you have a couple of options up here.

[00:17:26.000]
Use contacts above,

[00:17:28.240]
that will be a hot lode, hanging wall contact point.

[00:17:32.540]
If you use contacts below,

[00:17:33.984]
that’s going to be our footwall contact point.

[00:17:38.640]
If you press Okay,

[00:17:39.690]
we will create the contact points,

[00:17:42.000]
each of the intervals on that borehole.

[00:17:47.260]
So if I display them,

[00:17:48.430]
what we can see

[00:17:50.970]
is that contact points have been made on second borehole

[00:17:54.900]
and also the first borehole

[00:17:57.680]
on both the hanging wall and footwall sides

[00:18:01.890]
of the interval.

[00:18:03.420]
If you had multiple intervals throughout the borehole,

[00:18:06.000]
contact points we’ve made on each

[00:18:08.360]
based on the contacting

[00:18:11.310]
and ignore points that you’ve assigned.

[00:18:15.750]
Next is to assign these to the structure in the vein system

[00:18:20.470]
to allow leapfrog to know

[00:18:22.050]
to use this data to make the interpolation.

[00:18:25.281]
So if you navigate towards logical model

[00:18:27.540]
and the vein system,

[00:18:29.380]
we can see under the dropdown menus

[00:18:32.470]
options for the hanging wall and footwall data.

[00:18:36.140]
We can see the previous data that we’ve already used

[00:18:39.510]
for the polylines from the historic data.

[00:18:43.360]
But now we can right-click Add Data

[00:18:46.480]
and add point data

[00:18:48.170]
and navigate to the relevant contact point

[00:18:50.960]
for the hanging wall.

[00:18:52.220]
And we can do the same for the footwall.

[00:18:55.260]
Once this data is assigned,

[00:18:57.880]
leapfrog will automatically update the structure

[00:19:00.260]
based on the new borehole data.

[00:19:02.830]
If any other boreholes are drilled in the future

[00:19:05.390]
or any new intervals were made

[00:19:07.160]
in existing boreholes,

[00:19:08.930]
new contact points will be made for both hanging wall and footwall.

[00:19:12.633]
And the structure we automatically updated

[00:19:14.430]
with this new data.

[00:19:16.540]
That brings us down to my technical presentation.

[00:19:18.650]
I hope you enjoyed it.

[00:19:20.360]
I hope you learned a lot from it.

[00:19:22.060]
For any other questions,

[00:19:23.920]
You could also email me at the email address on this slide.

[00:19:28.050]
You can also find out more information on Cornish Lithium

[00:19:30.230]
at www.cornishlithium.com.

[00:19:33.310]
Again, thank you very much for listening.