FI20227096A1

FI20227096A1 - Method and system for analyzing drill cores

Info

Publication number: FI20227096A1
Application number: FI20227096A
Authority: FI
Inventors: Lasse Kangas; Ari Hartikainen; Jaakko Roima
Original assignee: Lumo Analytics Oy
Priority date: 2022-04-30
Filing date: 2022-07-06
Publication date: 2023-10-31

Abstract

This invention concerns analysis of drill cores resulting from mining operations, prospecting, and well drilling operations. The invention solves the problems of prior art by having the analysis system process drill cores one drill core box at a time, obtaining a three-dimensional (3D) point cloud representing the top surface of a drill core box (210) being analyzed and any drill cores (220) in the box with an optical scanner (290), having the control unit (270) of the analysis system determine from the 3D point cloud where there are drill cores in said drill core box, having the control unit determine (130) the location of the surface of a drill core at a plurality of locations, having the control unit direct (140) the measurement head of the analysis system to perform a laser-induced breakdown spectroscopy (LIBS) measurement at least a part of said plurality of locations, and having the control unit adjust (150) the focus of the measurement head at each measurement location according to the determined position of the surface of the drill core at the location.

Description

Method and system for analyzing drill cores 1. Field of the invention

This invention concerns analysis of drill cores resulting from mining operations, ore exploration, well drilling and concrete sampling operations. 2. Description of prior art

Examination of drill cores is an old technique to gain information about rock composition in various depths below the surface of the earth. Drill cores are produced with hollow drills that leave a core intact, which can then be raised from — the drill hole for analysis and storage. Drill core analysis is used in many different industries, such as in mining, in prospecting for minerals or oil, and in any situations where detailed information about composition of bedrock is desired.

Many different analysis methods are used in analyzing drill cores. Detailed information about the composition of a drill core can be obtained with X-ray fluorescence spectroscopy (XRF), which mainly provides information about elemental composition of a sample. Hyperspectral imaging can also be used to identify minerals in a sample.

N 25 Laser-induced breakdown spectroscopy (LIBS) is an analysis method in which

N surface of a sample is bombarded with a high peak power laser pulses which 5 removes some material from the surface, heating the removed material to a plasma

S state. The spectra produced by the produced plasma is analyzed for identifying the z elemental composition of the plasma, and consequently, of the surface at the point g 30 where the plasma was generated by the laser.

N

N Analysis systems are typically complicated, expensive and reguire specialized personnel to operate, whereby analyses are typically performed in a central laboratory, to which drill cores are transported from the drilling site. Transport delays and possible analysis queues cause unwanted delays, whereby on-site analysis would often be desirable.

Small handheld devices exist for performing e.g. LIBS or XRF measurements.

These are very useful for doing individual spot analyses onsite. However, handheld devices are quite cumbersome for thorough analysis of large numbers of cores.

A better system than known current systems is needed. An analysis system that could be deployed onsite would need to be simpler to use than typical current systems so that use of the system could be managed by personnel onsite at the drilling location. The system would also need to be able to cope with many different sizes and lengths of drill cores, even rubble, as drill cores may break even down to rubble depending on the consistency of the rock. Such a system would also need to be more economical to make it feasible to provide such a system onsite at a drilling — location.

SUMMARY OF THE INVENTION

The invention solves the problems of prior art by having the analysis system process drill cores one drill core box at a time, obtaining a three-dimensional (3D) point cloud representing the top surface of a drill core box being analyzed and any drill cores in the box with an optical scanner, having the control unit of the analysis system determine from the 3D point cloud where there are drill cores in said drill core box,

N 25 — having the control unit determine the location of the surface of a drill core at a

N plurality of locations, having the control unit direct the measurement head of the 5 analysis system to perform a laser-induced breakdown spectroscopy (LIBS)

S measurement at least a part of said plurality of locations, and having the control unit z adjust the focus of the measurement head at each measurement location according g 30 to the determined position of the surface of the drill core at the location. =

N

N In an embodiment of the invention optical scanner is a laser profile scanner which is used to scan the whole drill core box.

In an embodiment of the invention, the focus of the measurement head is adjusted by moving the measuring head in the vertical dimension to bring the surface of the drill core to focus distance.

In a further embodiment of the invention, the focus of the measurement head is adjusted by moving an optical element within the measurement head to change the focus distance to match the distance to the surface of the drill core.

In a still further embodiment of the invention, the measurement head comprises autofocus detection functionality for detecting whether the focus point is on the surface of the sample, or whether the focus point is above or below the sample.

Such functionality allows the analyzing system to correct small errors in focus at any measurement location. In a further embodiment of the invention, such autofocus mechanism is used for fine control of focus after coarse adjustment of focus based on the determination of surface location from said 3D point cloud.

A successful LIBS measurement requires a high power density of laser light on the surface of the sample, which practically requires that the laser light is well focused on the surface. In principle, it is possible to arrange an autofocus mechanism to manage the focus at all measurement locations. However, the inventors had the insight that determining the location of the drill core surfaces at various locations and using that information for adjusting focus at the same time as the measurement head is moved in the horizontal direction to the next measurement location allows higher scanning speeds, as there is no need to wait for the autofocus arrangement

N 25 to reach and stabilize at the correct focus point at each measurement location. This

N advantage allows fast scanning speeds and fast coverage of large areas, e.g. over 5 the whole top surfaces of a plurality of drill cores. 3 z In an embodiment of the invention, the control unit is arranged to plan a route for the g 30 measurement head based on said 3D point cloud in order to optimize the

N movements of the measurement head while performing LIBS measurements along

N the route.

In a further embodiment of the invention, the control unit is arranged to determine the speed of movement of said measurement head at a plurality of locations along said route at least in part based on said 3D point cloud. In such an embodiment, the control unit can optimize the scanning speed of the measurement head for each location. For example, at a location where a drill core is broken into pieces and the top surfaces of the core pieces are uneven, the measurement head may need to be moved much more in the vertical direction compared to scanning an intact drill core, whereby an optimal scanning speed may be different for different locations.

The recognition of where there are drill cores in the drill core box based on the 3D point cloud also reduces analyzing time, as that information can be used to skip scanning of sections of the drill core box which do not have a drill core present.

In an embodiment of the invention, the control unit is arranged to perform analysis of — the spectra resulted from a LIBS measurement in order to determine elements present at the measurement location. In a further embodiment of the invention the control unit is arranged to determine which minerals are present in the sample, based on the relative concentrations of elements.

In a still further embodiment of the invention, the analysis system comprises a communication unit for data communication with external networks and servers. In such an embodiment, the analysis system can send the results to a remote server or a cloud service for more thorough analysis of the measurement results. Such an embodiment is beneficial, since analyzing of the presence of minerals or other

N 25 compounds can be computationally heavy, and offloading heaviest calculations to

N remote services allows the analysis system to be light in computational resources 5 and thus of lower cost than a system capable of heavy calculations. 3 z The above summary relates to only one of the many embodiments of the invention g 30 disclosed herein and is not intended to limit the scope of the invention, which is set forth in the claims herein. These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will be described in detail below, by way of example only, with reference to the accompanying drawings, of which 5

Figure 1 illustrates a method according to an embodiment of the invention, and

Figure 2 illustrates a system according to an embodiment of the invention.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s), this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Features of different embodiments may be combined to provide further embodiments.

In the following, features of the invention will be described with a simple example of a method and system for drill core analysis with which various embodiments of the invention may be implemented. Only elements relevant for illustrating the embodiments are described in detail. Details that are generally known to a person skilled in the art may not be specifically described herein.

N 25 Figure 1 illustrates a method according to an embodiment of the invention. The

N method is performed by a drill core analyzing system for analyzing the elemental 5 content of drill cores. In this embodiment, drill cores are analyzed in batches of one

S drill core box at a time. In the example of figure 1, the method comprises the steps z of 3 30

N forming 110 a 3D point cloud representing the surface of a drill core box and drill

N cores in said drill core box using an optical scanner,

determining 120 from said 3D point cloud, where there are drill cores in the drill core box, determining 130 the position of the surface of a drill core at a plurality of locations on — said drill core from said 3D point cloud, performing 140 a LIBS measurement at at least a part of said plurality of locations, and adjusting 150 the focus of the measurement head at each measurement location according to the determined position of the surface of the drill core at the location.

Figure 2 illustrates a system 200 for analyzing the elemental content of drill cores according to an embodiment of the invention. Figure 2 illustrates schematically — several main components of the system.

The system has a measurement head 250 that comprises a laser unit 260, a laser cooling system 262, transmitting optics 264 for focusing the laser beam, as well as receiving optics 266 and a spectrometer sensor 267. The laser unit 260 can advantageously comprise a pulsed laser, as pulsed laser typically reaches high instantaneous power levels sufficient to ablate a part of the sample surface into plasma.

Figure 2 also illustrates an exemplary embodiment in which the measurement head comprises one, two or more sets of receiving optics 266 and one, two or more

N 25 spectrometer sensors 267. In this embodiment, these two sets are optimized for

N observing created plasma in different wavelength ranges: one of these sets is 5 optimized for visible wavelengths while the other is optimized for ultraviolet

S wavelengths. Having more than one set of receiving optics and a spectrometer z sensor allows covering of a wider wavelength range than with just one set. However, g 30 the invention is not limited to any specific number of these sets, as different

N embodiments of the invention may have one, two, three, or more sets of receiving

N optics and spectrometer sensors.

In a further embodiment of the invention the spectrometer sensor or sensors 267 are not situated in the measurement head, but the light gathered with receiving optics 266 is transferred to the spectrometer sensors 267 using one or more optical fiber cables. Such an embodiment allows the placement of the spectrometer sensors 267 in another location elsewhere in the system than within the measurement head, which reduces the mass of the measurement head. This is advantageous, since mass of the measurement head is one factor limiting the speeds in which the measurement head can be moved in different directions.

In an embodiment of the invention, the measurement head also comprises a nozzle connected to a blower unit for sucking air and dust from underneath the measurement head in order to remove dust produced by ablation of the sample surface by the laser.

The analyzing system 200 also comprises an arrangement for moving the measurement head 250 in three dimensions above the drill core box 210. The arrangement may comprise for example linear actuators or for example stepper motors moving the measurement head along linear guide rails. As an example, figure 2 shows a vertical rail 280 attached to the measurement head 250, which vertical rail 280 is moved in the vertical rail by a stepper motor 281. Figure 2 also illustrates another stepper motor 283 moving the vertical rail 280 and consequently the measurement head 250 in a horizontal direction along a horizontal rail 282. A man skilled in the art knows many ways of arranging for moving an element in three dimensions under control of a control unit, wherefore these arrangements are not

N 25 described in any further detail in this specification.

O

N

5 Figure 2 also illustrates an optical profile scanner 290 attached to the measurement

S head 250. In an embodiment of the invention, before performing LIBS z measurements, the system scans the drill core box and drill cores with the scanner g 30 290 for obtaining a 3D point cloud representing the surface of the drill core box and

N any drill cores or pieces of drill cores within the box. The system then can use the

N 3D point cloud for controlling focus during LIBS measurements. In further embodiments of the invention, the system can use the 3D point cloud for determining a route for the measurement head to follow for performing the LIBS measurement, and for determining an optimal speed of movement of the measurement head along such a route. The optical profile scanner 290 can for example be a laser profile scanner or any other device that can provide a 3D point cloud representation of a surface, such as a LIDAR device or the optical profile scanner 290 can determine the 3D point cloud using stereophotogrammetry.

Figure 2 also shows the control unit 270 for controlling the functioning of the analyzing system. In the embodiment illustrated in figure 2, the control unit comprises a processor 271, a memory element 272, and communication unit 273.

The processor 271 can be any type of processor capable of executing instruction sets stored in a memory element.

The memory element 272 can in different embodiments of the invention be implemented in many ways known to a man skilled in the art. The memory element 27/2 can comprise transient memory elements such as random-access memory (RAM), and/or non-transient storage such as FLASH memory, magnetic disk based memory such as hard disks, or for example SSD disks.

The communication unit 273 can comprise for example circuitry for communicating via a wireless local area network (WLAN), or for example circuitry for communicating via a wireless cellular data transmission network. The communication unit 273 can in further embodiments of the invention also comprise circuitry for communicating via a wired connection such as an Ethernet connection. The communication unit allows connection to remote servers and cloud services which in various

N 25 embodiments of the invention can be used for further processing of the

N measurement data such as for more detailed analysis and visualization of data, and 5 for storing of measurement data. 3 z The analyzing system 200 also comprises further electronics for aiding in the control g 30 of the system such as motor drivers and power sources. These can be implemented

N in the control unit, or as separate modules within the system. Various arrangements

N of these are well known to a man skilled in the art, whereby they are not described in further detail in this specification.

Figure 2 also shows a drill core box 210 placed in the system for analysis. The drill core box 210 holds in the example of figure 2 a plurality of drill cores 220. In the example of figure 2, the system 200 also comprises rollers 201 that enable smooth and easy positioning of drill core box within the system.

In an embodiment of the invention the control unit comprises software which in addition for controlling the system provides functionality for data collection and storage, processing of data, analysis of measurement data and visualization of analysis results. In such an embodiment, the analysis system can provide measurement and analysis results locally, even if the system comprises no communication unit or if the site where the system is located does not have a data communication link to remote data networks.

In the following we describe an example of how a typical analysis procedure for analyzing a drill core box proceeds in the analysis system 200 shown in figure 2 according to an embodiment of the invention. The actions described here are performed by the control unit as directed by software executing on the processor of the control unit. The drill core box is scanned with the optical profile scanner to acquire a 3D point cloud representing a detailed surface map of the whole drill core box and any drill cores within it. Rock sample locations are determined from the point cloud data using measured intensity values and/or object recognition. An optimal movement route of the measurement head is calculated from the point cloud data. Measurement locations are determined based at least partly on determined surface locations of the drill cores and scanning resolution selected by a user of the

N 25 system. The LIBS measurements are executed along the predetermined areas by

N moving the measurement head over the samples along the determined route. The 5 laser and spectrometers are triggered when the measurement head reaches a

S predefined measuring point.

E

3 30 In an embodiment of the invention, calculation of the movement route of the measurement head involves determination of coordinates of surface locations from the point cloud data, and determination of an optimal movement from a measurement location to the next measurement location, which minimizes time spent moving the measurement head to the next location. The measurement speed of the system is limited - among other factors - by the speed of movement in lateral and in vertical dimension. Since drill cores are long cylinders, one optimal solution is to maximise horizontal movement and minimize vertical movement by moving the measurement head from end to end of a drill core and performing measurements along that line of movement, before changing the vertical and crosswise positions and repeating the movement back to the other end of the drill core. Such a route would on average minimize movement of the measuring head between measurement locations.

The invention has many benefits. The invention provides a method and a system for analyzing drill cores, which can analyze a whole drill core box at a time, saving analyzing time. The invention also provides a system that can perform this analysis automatically, without requiring specialists to handle the system. Offloading more data processing and analysis to a remote server or a cloud service allows the processor of the system to be a relatively low power and economical processor, as high-end data processing capacity is not needed at the system. Providing the measurement results to a remote server or a cloud service also allows access for analysis experts in an event where review and analysis of an expert is needed. All these benefits make it feasible to provide an analysis system on-site at a mine or at an exploration project, whereby the system can provide quick insights to geologists and other users to support their decision making in operative mines or in ore exploration projects.

N 25 CERTAIN FURTHER EMBODIMENTS OF THE INVENTION

O

N

5 In the following, we describe a number of embodiments of the invention.

S

E According to a first aspect of the invention, a method for analyzing the elemental 3 30 content of drill cores is provided, the method being performed by a drill core

N analyzing system. In a first embodiment according to this first aspect of the

N invention, drill cores are analyzed in batches of one drill core box at a time, and the method comprises at least the steps of forming a 3D point cloud representing the surface of a drill core box and drill cores in said drill core box using an optical scanner, determining from said 3D point cloud, where there are drill cores in the drill core box, determining the position of the surface of a drill core at a plurality of locations on said drill core from said 3D point cloud, performing a laser induced breakdown spectroscopy measurement at at least a part of said plurality of locations, and adjusting the focus at each measurement location according to the determined position of the surface of the drill core at the location.

In a second embodiment of this first aspect of the invention, the method further comprises at least the steps of determining the route of the measurement head of the drill core analyzing system for analyzing the elemental content of said drill cores in said drill core box at least in part based on said 3D point cloud, and performing laser induced breakdown spectroscopy measurements along said route.

In a third embodiment of this first aspect of the invention, the method further

N 25 comprises at least the step of determining the speed of movement of said

N measurement head at a plurality of locations along said route at least in part based 5 on said 3D point cloud.

O

O z According to a second aspect of the invention, a system for analyzing the elemental 3 30 content of drill cores is provided. The system has a control unit for controlling the

N operations of the system. In a first embodiment according to this second aspect of

S

N the invention, the system comprises at least a measurement head for performing laser induced breakdown spectroscopy measurements under control of the control unit, an arrangement for moving said measurement head in three dimensions over a drill core box placed in said system for analysis, an optical scanner for measuring the location of the surface of a drill core box and of any drill cores in said drill core box, and the control unit is arranged to read measurement results from said optical scanner and for forming a 3D point cloud from said measurement results, — to determine from a formed 3D point cloud where there are drill cores in the drill core box, to determine the position of the surface of a drill core at a plurality of locations on said drill core from said 3D point cloud, to direct said measurement head to perform a laser induced breakdown spectroscopy measurement at at least a part of said plurality of locations, and to adjust the focus of the measurement head at each measurement location

N 25 according to the determined position of the surface of the drill core at the location. & 5 In a second embodiment according to this second aspect of the invention, the

S control unit is arranged x a 8 30 to determine the route of the measurement head of the drill core analyzing system for analyzing the elemental content of said drill cores in said drill core box at least in part based on said 3D point cloud, and to direct said measurement head to perform laser induced breakdown spectroscopy measurements along said route.

In a third embodiment according to this second aspect of the invention, the control — unit is arranged to determine the speed of movement of said measurement head at a plurality of locations along said route at least in part based on said 3D point cloud.

CERTAIN FURTHER OBSERVATIONS

In view of the foregoing description, it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention. While a preferred embodiment of the invention has been described in detail, it should be apparent that many modifications and variations thereto are possible, all of which fall — within the true spirit and scope of the invention.

It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

Reference throughout this specification to “one embodiment” or “an embodiment”

N 25 means that a particular feature, structure, or characteristic described in connection

N with the embodiment is included in at least one embodiment of the present 5 invention. Thus, appearances of the phrases “in one embodiment” or “in an

S embodiment’ in various places throughout this specification are not necessarily all z referring to the same embodiment. © 30

R As used herein, a plurality of items, structural elements, compositional elements,

N and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unigue member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the previous description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention.

One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

While the foregoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below. e 25

S

5 LIST OF CERTAIN TERMS AND THEIR REFERENCE NUMBERS USED IN THIS

S SPECIFICATION ie a 3 30 measurement head 250

N laser unit 260

N laser cooling system 262 transmitting optics 264 receiving optics 266 spectrometer sensor 267 drill core 220 drill core box 210 vertical rail 280 horizontal rail 282 stepper motor 281, 283 optical profile scanner 290 control unit 270 processor 271 memory element 272 communication unit 273 roller 201 system 200 for analysing the elemental content of drill cores

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Claims

1. Method for analyzing the elemental content of drill cores, the method being performed by a drill core analyzing system, characterized in that in the method, drill cores are analyzed in batches of one drill core box at a time, and the method comprises at least the steps of forming a 3D point cloud representing the surface of a drill core box and drill cores in said drill core box using an optical scanner, determining from said 3D point cloud, where there are drill cores in the drill core box, determining the position of the surface of a drill core at a plurality of locations on said drill core from said 3D point cloud, performing a laser induced breakdown spectroscopy measurement at at least a part of said plurality of locations adjusting the focus at each measurement location according to the determined position of the surface of the drill core at the location. N 25 2.A method according to claim 1, characterized in that the method further

O . N comprises at least the steps of K <Q S determining the route of the measurement head of the drill core analyzing system for z analyzing the elemental content of said drill cores in said drill core box £ 30 O N at least in part based on said 3D point cloud, and S N performing laser induced breakdown spectroscopy measurements along said route.

3. A method according to claim 1, characterized in that the method further comprises at least the step of determining the speed of movement of said measurement head at a plurality of locations along said route at least in part based on said 3D point cloud.

4. System for analyzing the elemental content of drill cores, the system having a — control unit for controlling the operations of the system, characterized in that the system comprises at least a measurement head for performing laser induced breakdown spectroscopy measurements under control of the control unit, an arrangement for moving said measurement head in three dimensions over a drill core box placed in said system for analysis, an optical scanner for measuring the location of the surface of a drill core box and of any drill cores in said drill core box, and in that, that the control unit is arranged to read measurement results from said optical scanner and for forming a 3D point N 25 cloud from said measurement results, O N 5 to determine from a formed 3D point cloud where there are drill cores in the drill core S box, ie a 3 30 to determine the position of the surface of a drill core at a plurality of locations on said drill core from said 3D point cloud, N to direct said measurement head to perform a laser induced breakdown spectroscopy measurement at at least a part of said plurality of locations, and to adjust the focus of the measurement head at each measurement location according to the determined position of the surface of the drill core at the location

5. A system according to claim 4, characterized in that the control unit is arranged to determine the route of the measurement head of the drill core analyzing system for analyzing the elemental content of said drill cores in said drill core box at least in part based on said 3D point cloud, and to direct said measurement head to perform laser induced breakdown spectroscopy measurements along said route.

6. A system according to claim 4, characterized in that the control unit is arranged to determine the speed of movement of said measurement head at a plurality of locations along said route at least in part based on said 3D point cloud. N QA O N K <Q O O I Ao o i O O N N QA O N