Deep cover mineral exploration: The Coil Tubing Rig

Deep cover. The term is regularly used in exploration circles to describe areas which have thick, barren, and often unconsolidated sediments overlying prospective exploration targets. What makes these sediments an issue is not the fact that they’re unprospective for any hard-rock metallic deposits, but rather the drilling difficulties or depth restrictions that are encountered using existing and proven drilling methods such as diamond drilling and reverse circulation (RC), respectively.

Enter the Deep Exploration Technologies Cooperative Research Center (DET CRC) which has been working to develop research projects on the subject of successful, cheaper and safer drilling technologies for use in deep target exploration through barren cover. The CRC is an Australian federal initiative setup to drive initial research into fields that can potentially deliver significant economic, environmental, and social benefits which have the potential to develop further without government funding.

The DET CRC commenced in 2010 and is planned operate until the end of 2017. The program is funded by $30M from the Commonwealth Government, $2M plus $5M in-kind from the South Australian Government, $41M in-kind from research participants, and $25M from industry participants including AngloAmerican, Barrick Australia, BHP Billiton, Boart Longyear, Imdex Ltd, and Vale.

The project is split into three streams:

  • Project 1: Drilling
    • Development of an operational coil tubing rig
    • Drilling management and optimisation
  • Project 2: Logging and Sensing
    • Development of ‘logging while drilling’ technologies such as downhole magnetic susceptibility, spectral gamma, and downhole resistivity
  • Project 3: Targeting
    • Development of cost-effective seismic techniques

The Technology – Coil Tubing Drilling

Coil tubing (CT) drilling is not a new concept. The technology has been used for over 20 years in the oil and gas industry and is commonly utilised in conjunction with directional drilling technologies. However, CT drilling has never been successfully applied to land based mineral exploration.

The goal of the CT drilling program is to deliver a functioning and reliable drilling technology capable of drilling to 500 metres, weighing less than 10 tonnes, and at a cost of <$50 per metre.

The fundamental advantage of a coil drilling technique over conventional drilling technologies is the elimination of drill rods. Removing drill rods means no rod handling which is both faster and safer and the result is continuous drilling, maintained hole pressure (which significantly increases drillhole stability), and fast retraction of the coil which is projected to be 30 m/min.

Circulation will be conventional, with fluid pumped down the coil, through the drill bit, and up the annulus of the drillhole. The drill bit will be powered by a downhole motor due to the inability of the coil to spin. The coil is held on a large spool which spins to release or collect the coil. However, there are a number of challenges facing the development of this technology. With CT drilling relying on fluid driven sample transport within the drillhole there are two obvious hurdles; 1, the flow of water within the annulus can lead to sample contamination by the inclusion of wall-rock (especially when drilling through poorly consolidated sediments); and 2, the method will rely on clean water being pumped into the drill string. The second hurdle will require on-rig water cleaning and separation of cutting from the returning water.

 

Coil fatigue is a major concern in the development process of the technology. Each time the coil is bent there is an element of fatigue that impacts its longevity. Coils currently being used in oil and gas drilling applications can withstand between 30 and 200 bend occurrences, with the critical number depending on operating conditions. The DET CRC hoped to develop a coil capable of withstanding a minimum of 300 bends, allowing a single coil to last a maximum of 50 drillholes, with a minimum of 6 coil bends per drillhole. Currently, coil testing has been completed on a variety of coils with current iterations lasting over 900 bends, bringing the maximum number of drillholes per coil up to 150.

The RoXplorer®

roxplorer_rig

In November of 2016 the DET CRC launched the RoXplorer®, the latest version of the programs CT rig. The details of the rig are not publicly available with the rig undergoing extensive testing over the next year.

In a trial drillhole completed at the Brukunga test facility in South Australia, a 165 m drillhole was completed in 12 hours using a fluid driven percussion setup accompanied by fluid recycling with fluid being cleaned to an average of <400mg/l solids. Improvements in fluid return have been significant with 85% fluid recovery over a 65,000 litre test increasing from 45% in earlier testing.

The Autosonde™

The Autosonde™ is essentially a downhole probe with the ability to be used while rods are being pulled. Functioning sensors currently includes magnetic susceptibility and spectral gamma, but the probe will eventually include galvanic resistivity (currently in prototype stage).

The Autosonde™ is lowered inside the drill string to the bottom of the hole on completion of the drillhole and the various sensors record as the rods are pulled. The tool has many benefits especially in saving time by reducing wireline logging and core logging activities and, with the inclusion of a survey tool, time lost during survey collection will be eliminated.

The DET CRC has signed an exclusive agreement for the Autosonde™ with Boart Longyear and it is not yet known when the tool will be commercially available.

Outlook

The DET CRC has no definitive projection for when CT drilling will be commercially available however Project CEO, Prof. Richard Hillis is hopeful for a date sometime before 2020. Details on commercial availability are also uncertain, with Boart Longyear and Imdex Ltd having the first right to license the technology it is likely that one of the two companies will gain exclusive rights to CT drilling, producing CT rigs for sale on the open market.

The prospect of cheap drilling through barren cover at <$50 per metre is exciting. With RC and diamond costs (contractor only) in the order of $100/m and $170/m, respectively, the opportunities in brownfields, greenfields and blue sky terranes are undeniable. Of course, only time will tell if the technology works well and at the proposed price point.

Further Information

DET CRC Website:  http://detcrc.com.au/

 

 

 

 

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Tectonic processes replicated in small scale models

One of the more interesting aspects of geology is the concept of a dynamic earth. The aspect of geology that most interests me, and has done for many years, is large-scale tectonics and structural geology. What makes it so interesting is not only the scale of the processes that  occur but the range of features that can result at smaller scales. These tell-tale signs at the outcrop-scale are what entices  a structural geologist, and the ability to observe, identify, record, synthesise, and interpret these features is what make a great structural geologist.

Since July 2013, Dr. Philip Prince of Virginia Tech has been publishing sandbox-style geological models to YouTube on his channel ‘TheGeoModels‘. These models range in complexity and include generic models of structural settings, and real-world analogues such as the Appalachian Mountains which include supporting videos filmed on outcrops to discuss outcrop-scale features such as fabrics, folds, rock types, and mineralogy.

The videos portray interesting structural stories which include ongoing commentary to assist in explaining the ongoing development of the respective geological setting.

Below are two contrasting structural settings:

  • The first video shows the development of a rift basin (extension) followed by an inversion (later shortening). The model does a great job of exhibiting the faults that typically form and how faults interact and reactivate in an evolving structural regime.  What’s great about this example is that it show how complex real-world geological settings can be; I regularly remind myself of the phrase commonly used by renowned structural geologist Rick Sibson – “Mother Nature is a bitch”.

 

 

  • The second video, entitled “Mountain building: Uplift, erosion and exhumation” shows the development of thrust sheets and the process of tectonic burial during a continent-continent collision event. This video does a great job of also displaying the process of erosion and providing a look into the structures and orientations you might expect to observe at certain parts of an active or completely eroded orogen (such as an Archean orogen).

 

 

So take the time to watch a few of these videos. Many of the concepts are well known by geologist however the details are typically overlooked, yet very important when trying to convey an interpretation of you own…

For many more videos by Dr. Philip Prince go to:

https://www.youtube.com/user/TheGeoModels

Dr. Philip Prince also maintains a website with articles on the models and geology in the real world:

https://geomodelsvt.wordpress.com/

 

 

 

 

Visual Geology: 3D learning tool

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A few months back I came across an interesting web application that allows you to control and visualise geological features in 3D space, all from a web browser.

It’s called Visual Geology Beta and it was created by Rowan Cockett, an undergraduate engineering geology student at the University of Calgary, Canada. It all started in MATLAB, and after approaching an introductory geology instructor, the application was put to the web.

The basic concept behind the visualisation object is to help the teaching of 3D geology. One of the most difficult tasks for any young geology student is developing their three dimensional abilities, and this program is a great tool for doing exactly that. Here I will give a few screengrabs from some of the 3D processes that can be executed.

beds

Here we have a dialog which allows the user to add beds of varying description and thickness. Colours, names and details can be edited to simulate real-world examples.

tilting

Here we add a hypothetical plane by which to tilt the strata. The orientation of the tilt plane can be modified using the dialog box (displayed).

tilted

And the result, a stratigraphic package with an orientiation of 46/090 (dip/dipdir).

folding

Fold generations can be applied to the model as well. In this example I have added a recumbent, tight fold generation to overprint the previous tilt episode. Specific fold characteristics can be manipulated including period, amplitute, shape and offset to generate particular fold styles. Fold interference patterns can also be produced by applying multiple overprinting fold generations.

folded

and the result, a tilted stratigraphic package which has subsequently been overprinted by a recumbent fold event (D1).

There are many more features that can be added to a model including:

  • Unconformities
  • Dykes
  • Faults
  • Thrusts
  • Topography
  • Stereonets
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Here is an example of a model with topography applied. From this it is easy to see how the application could be a powerful learning tool

Other features that can be of use include the cross section module. This gives a cross section through any designated slice of the cube and displays it above the object.

generate_cross_section

Applications in mineral exploration

Realistically, an application such as this has no significant potential in the mineral exploration industry. Commercial packages such as Leapfrog Geo provide much more powerful and realistic tools for modelling. However it is worth mentioning that the apparent dip calculator is useful, and I have personally used this in my work because of its accessibility online.

Overall this is an interesting tool that serves, in my opinion, as a tool for teaching and displaying geological concepts to student and non-geologist. But it’s cool! So if you have a spare half hour, go have a play here:

http://app.visiblegeology.com/

Discovering the Tropicana Gold Deposit

3D

Stream here – or subscribe on iTunes

In Geoscience Radio’s first podcast, we delve into the discovery of the Tropicana gold deposit. We talk to Bruce Kendall of Blackham Resources (previously Senior Geologist at AngloGold Ashanti during the discovery period) and discuss the exploration that went into this amazing discovery and hear about the events that were important in getting there.

The story  of Tropicana began in 1993 with the discovery of the Voisey’s Bay Ni-Cu-Co deposit. The discovery of this world-class deposit set off a chain of events that would eventually lead to the discovery of one of Western Australia’s most significant gold discoveries in recent history.

The deposit (and now mine) is located on the eastern margin of the Yilgarn craton, 330 Km ENE of Kalgoorlie and is jointly owned by AngloGold Ashanti and Independence Group NL.

Subscribe via iTunes, or listen here on GeoscienceRadio.com


References:

Crawford, A.J., and Doyle, M.G., 2016, Granulite-Hosted Gold. Tectonic setting and lithogeochemistry of the Tropicana deposit, Western Australia. Economic Geology, v. 111, p. 395-420.

Blenkinsop, T.G., and Doyle, M.G., 2014, Structural controls on gold mineralisation on the margin of the Yilgarn craton, Albany-Fraser Orogen: The Tropicana deposit, Western Australia. Journal of Structural Geology, v. 67, p. 189-204.

Mickinnon-Matthews, J., 1998, Annual report for the Pleiades Lakes project. WMC Resources Ltd.

Mickinnon-Matthews, J., 1999, Surrender report for the Pleiades Lakes project. WMC Resources Ltd.

Perkins, M., 2004, Annual report for tenements for the Tropicana East JV. AngloGold Ashanti, Independence Group NL and Southstar Diamonds. E39/951, E39/952, E39/956, E39/1008, E39/1009, E39/1010, E39/1016 and E39/1090.

Perkins, M., 2005, Surrender report – Tropicana JV. AngloGold Ashanti, Indepedence Group NL and Southstart Diamonds. E39/954.

McCarthy, M., 2005, Annual report for tenements for the Tropicana Project – Tropicana Group 1. AngloGold Ashanti, Independence Group NL and Southstar Diamonds. E39/951, E39/952, E39/956, E39/1008, E39/1009, E39/1010, E39/1016 and E39/1090.

Wilson, D., 2006, Annual Report – Tropicana Project – Tropicana group 1. AngloGold Ashanti, Indepenence Group NL.E39/951, E39/952, E39/956, E39/1008, E39/1009, E39/1010, E39/1016 and E39/1090.


Music (in order of appearance):

  • Kevin MacLeod. “Hustle”. 2011. Blues Sampler.
  • Laszlo Harsanyi. “The tiki bar”. 2016. Tropical Breeze.
  • Transient. “Conduit”. 2016. Path-01
  • Transient. “Cure for the common cold”. 2016. Path-01.
  • Blue Dot Sessions. “Zeppelin”. 2015. Aeronaut.
  • Mathieu Lamontagne & Emmaluel Toledo. “Avant”. Year not specified. Album not specified.
  • Broke For Free. “Something elated”. 2011. Something EP.