GB2622624A

GB2622624A - A drill core sample block

Info

Publication number: GB2622624A
Application number: GB2213911.7A
Authority: GB
Inventors: Nikolai Eide Nilsen Omma Henrik; Helena Eide Omma Panayi Jenny; Rusnac Valentin
Original assignee: Rocktype Ltd
Current assignee: Rocktype Ltd
Priority date: 2022-09-23
Filing date: 2022-09-23
Publication date: 2024-03-27
Also published as: GB202213911D0

Abstract

A drill core sample block 1 comprises a body 3 within which a plurality of elongate drill core sticks 5 are embedded. Each drill core stick 5 has been obtained from a drill core and has an inspection face 7 that faces outwardly from the body 3. The drill core sticks 5 may be arranged so that the longitudinal axes X-X are parallel. The inspection faces 7 of the drill core sticks 5 may be parallel and located within a single plane. The drill core sticks 5 may be spaced apart from each other. The body 3 may be made from an epoxy resin. Also disclosed is a method for producing a drill core stick 5 for a drill core sample block 1 from a drill core sample strip (75, fig 9), wherein the drill core sample strip (75, fig 9) is produced by cutting a drill core in half along its length and by making a thicknessing cut (C1, fig 11) along one drill core half (71, fig 9) parallel to the longitudinal axis X-X of the drill core half.

Description

A DRILL CORE SAMPLE BLOCK

Scanning electron microscopes (SEMs) are used for material analysis of geological samples to obtain petrographic data, such as information on the mineral content of rock. One source of petrographic data is a drill core, which is a cylinder of rock extracted using a core drill. Drill cores are typically long, for example up to 3,000m long. It is known to scan the entire length of a drill core using techniques such as infrared spectroscopy, optical analysis of photographs and X-ray scanning. Such techniques scan a drill core that has been cut in half lengthways. However, it is not practical to undertake an inspection of halved drill cores using a SEM io because the scanning area of an SEM is small and consequently it takes a long time to scan each length of halved drill core. At present, if a drill core needs to be inspected using a SEM then a sample plug is taken from the drill core in a direction perpendicular to its longitudinal axis. This sample plug can then be processed to facilitate a SEM inspection. However, the sample plug only provides petrographic data for one position on the drill core. Additional sample plugs can be extracted to give petrographic data for other positions on the drill core, but it is not possible using this technique to inspect the entire length of a drill core, nor to readily automate the inspection process to increase the quantity of the petrographic data that is obtained. Machine learning analysis can be applied to the data obtained from SEM inspection of the sample plugs, but that analysis is inherently limited due to the sample plugs only providing samples at discrete positions along the drill core. In addition, if the sample plugs are taken at locations that are selected by a person, for example because that person perceives that the drill core is geologically interesting at those locations, then there is possibility of introducing an unclear bias into the data set.

As mentioned above, once a length of drill core has been extracted it is usual for it to be cut in half along its length to produce two pieces, each with a semi-circular cross-sectional profile. Current techniques do not produce inspection samples corresponding to the entire length of the drill core, but only produce samples for particular positions along the length, through the use of sample plugs, as explained above. There is therefore a need for a technique that can be used to produce inspection samples that correspond to the entire length of the drill core and can be subjected to inspection using a SEM in an efficient manner.

Accordingly, the present invention provides a drill core sample block comprising a body within which a plurality of elongate drill core sticks are embedded, wherein each drill core stick has an inspection face that faces outwardly from the body and wherein each drill core stick has been obtained from a drill core. As a result of embedding the drill core sticks within the body, the drill core sticks are protected during the inspection process and during subsequent storage, and therefore are less susceptible to falling apart, which might occur if the material of the drill core is inherently fragile or friable, or if the drill core sample block is subjected to any shock loads, for example as might result from the drill core sample block being dropped. In addition, placing the drill core sticks within a drill core sample block removes the need to have a separate holder for insertion of the drill core material into the scanning electron microscope and thereby maximises the useable amount of the scanning area.

Preferably, the drill core sticks are arranged so that the longitudinal axes X-X of the drill core sticks are parallel. A parallel arrangement of the drill core sticks is advantageous because it helps to maximise the amount of drill core material that can be inspected by a scanning electron microscope each time that a drill core sample block in inserted into the scanning electron microscope.

Preferably, the inspection faces of the drill core sticks are parallel to each other. This facilitates manufacture of the drill core sample block and subsequent inspection of that drill core sample block using a scanning electron microscope.

Preferably, the inspection faces of the drill core sticks are located within a single plane. This facilitates manufacture of the drill core sample block and subsequent inspection of that drill core sample block using a scanning electron microscope.

Preferably, the drill core sticks are spaced apart from each other. Spacing the drill core sticks apart from each other is advantageous because it facilitates automation of the scanning process. The spaces enable one drill core stick to be distinguished from its neighbour.

Preferably, the body is made from an epoxy resin. Use of an epoxy resin is advantageous because it can be poured into the sample block mould in liquid form and then, once cured to a solid, the epoxy resin provides a robust material for the body of the drill core sample block.

Preferably, a mounting arrangement is provided on the body.

Preferably, the mounting arrangement has at least one attachment aperture and wherein the attachment aperture is offset from a central axis Y-Y of the drill core sample block. The asymmetrical arrangement of the attachment aperture is advantageous because it avoids the possibility of the drill core sample block being placed into the scanning electron microscope in the wrong orientation.

Preferably, the mounting arrangement has at least one bonding aperture.

Preferably, the mounting arrangement has a planar mounting surface and the inspection face of each drill core stick is parallel to the mounting surface. This facilitates location of the inspection faces within the scanning electron microscope in an orientation that is parallel to the scanning plane.

Preferably, the mounting arrangement is a mount plate. The mount plate prevents the drill core sample block from warping, either in use, or during storage. If the drill core sample block becomes warped then it might not fit into the scanning electron microscope, or the quality of the data from the scanning might be compromised.

Preferably, the drill core sample block has an inspection surface that is parallel to and coplanar with each of the inspection faces. This facilitates manufacture of the drill core sample block and subsequent inspection of that drill core sample block using a scanning electron microscope.

Preferably, at least part of the external surface of each drill core stick is provided with a stabilising layer. The stabilising layer is advantageous because it stabilises at least part of the external surface of each drill core stick thereby reducing the possibility of it falling apart prior to being embedded with the drill core sample block.

Preferably, the stabilising layer is made of epoxy resin. It is easy to apply the epoxy resin to the external surface of the drill core and it cures to form a hard and tough layer. Also, the epoxy resin stabilising layer will readily adhere to the epoxy resin from which the body of the drill core sample block is made.

Preferably, the drill core sticks represent a continuous length of drill core.

Preferably, there are eight drill core sticks, each of approximately 70mm in length, representing approximately a 560mm length of drill core. Different lengths of drill core sticks are envisaged by the present invention. The length of the drill core sticks can be selected according to factors such as the specification and type of the equipment available for preparing the drill core sample blocks. Particular types of equipment may facilitate making larger drill core sample blocks. For example, drill core sample blocks with dimensions of 150mm x 150mm could be made, which could represent a length of drill core of approximately 3m. Drill core sticks are nominally 70mm in length, but may be slightly shorter, for example 68mm long, as a result of the process of cutting the drill core sticks using a saw blade that removes 1-2mm of material with each cut.

Preferably, the inspection face of each drill core stick is generally rectangular and is approximately 70mm long parallel to the longitudinal axis X-X and approximately 7mm wide perpendicular to the longitudinal axis X-X.

Preferably, the body is cuboidal and the inspection surface is square and has a dimension of up to 150mm x 150mm. Alternatively, the inspection surface could be rectangular. The inspection face need only be slightly larger than the area taken up by the drill core sticks. For example the inspection surface could be 72mm x 76mm.

Preferably the body has a depth of 14mm. For example, the resin slab can be 9mm thick and the aluminium alloy mount plate can be 5mm thick.

The present invention also provides a method of inspecting a drill core using a drill core sample block, wherein the drill core sample block is placed into a scanning electron microscope and the scanning electron microscope is used to inspect an inspection face of a drill core stick.

Preferably, a central inspection portion of each inspection face is scanned by the scanning electron microscope.

The present invention also provides a method for producing a drill core stick, for a drill core sample block, from a drill core sample strip, wherein the drill core sample strip is produced by cutting a drill core in half along its length and by making a thicknessing cut along one drill core half parallel to the longitudinal axis X-X of the drill core half. It is advantageous to take the sample strip from the edge of the drill core because it leaves a substantial portion of the drill core intact for future analysis and because a smaller rock saw with a smaller diameter and thinner saw blade can be used.

Preferably, each drill core stick has an inspection face and the inspection face of each drill core stick is substantially perpendicular to the plane of the cut. This facilitates creation of the inspection face by making only one further cut.

Preferably, the thicknessing cut is substantially perpendicular to the diametrical cut face of the drill core half. This is advantageous because it means that the inspection face of each drill core stick is representative of a portion of the diametrical face of the drill core half. This makes it easier to match data obtained from the inspection face with other data that may have been collected for the diametrical face of the drill core half, for example by utilising techniques such as X-ray fluoroscopy, infrared imaging and photography. This is particularly advantageous when employing machine learning techniques to identify any patterns that are common to different data sets.

Preferably, a depth cut is made through the drill core sample strip in a direction perpendicular to the thicknessing cut. This depth cut produces a primary drill core sample and a secondary drill core sample.

The present invention will be described with reference to the following figures: Figure 1 is a perspective view of a drill core sample block according to the present invention; Figure 2 is a perspective view of a drill core stick that has been cut from a drill core and has not yet been embedded in the drill core sample block of Figure 1; Figure 3 is a plan view of the drill core sample block of Figure 1; Figure 4 is a transverse cross-sectional view of the drill core sample block of Figure 1 along central transverse axis Y-Y of Figure 3; Figure 5 is a plan view of the mounting surface side of a mount plate of the drill core sample block of Figure 1; Figure 6 is a perspective view of a drill core sample block of Figure 1 fixed to a small interface plate; Figure 7 is a is a perspective view of four drill core sample blocks of Figure 1 fixed to a large interface plate; Figures 8 is a perspective view of a sample block mould for moulding the drill core sample block of Figure 1; Figure 9 is a perspective view of a drill core cut in half along its longitudinal axis X-X to produce two drill core halves, with one drill core half showing the portions of the drill core that form the primary drill core sample strip and the secondary drill core sample strip.

Figure 10 is an end view of a drill core half located within an angle profile during a stabilisation step of the sample block manufacturing process; Figure 11 is an end view of the drill core half of Figure 10 during a thicknessing cutting step of the sample block manufacturing process in which a drill core sample strip is produced Figure 12 is an end view of the drill core sample strip of Figure 11 during a depth cutting step of the sample block manufacturing process in which primary and secondary drill core sample strips are produced; and Figure 13 is a transverse cross-sectional view of a part-finished drill core sample block of Figure 1 along the central transverse axis Y-Y, prior to a final grinding / polishing step.

A drill core sample block 1 according to the present invention is shown in Figure 1. The drill core sample block 1 comprises a cuboidal body 3 made from epoxy resin within which are embedded eight drill core sticks 5. Each drill core stick 5 has an inspection face 7 that faces outwardly from the body 3 and the inspection faces 7 are parallel and co-planar with each other and are located on an inspection surface 9 of the body 3. An aluminium alloy mount plate 11 is fixed to the opposite side of the body 3 to the inspection surface 9.

A drill core stick 5 is shown in Figure 2, isolated from the drill core sample block 1 for ease of illustration of its features. The inspection face 7 is elongate and rectangular with a width W1 of 7mm and a length L1 of 70mm. The inspection face 7 is polished to a surface finish that facilitates inspection of the drill core stick using a scanning electron microscope. The drill core stick 5 also has a thicknessing face 13, which is perpendicular to the inspection face 7, and a depth face 15 which is parallel to the inspection face 7 and perpendicular to the thicknessing face 15. The fourth side of the drill core sfick 5 is a drill core face 17, which is the external surface of the drill core half 71 from which the drill core sticks 5 are cut during the manufacturing process. A sectioning face 19 is provided at each end of the drill core stick 5 and a longitudinal axis X-X runs between the sectioning faces 19. The drill core face 17 is covered with a stabilising layer 21 made from epoxy resin. The method of manufacture of the drill core stick 5 to produce its six faces will be explained below.

The drill core sticks 5 are arranged in parallel within the body 3 of the drill core sample block 1, for example as shown in Figure 3. The longitudinal axes X-X of the drill cores sticks 5 run perpendicularly to the end faces 23 of the body 3. The body 3 has a width W2 of 76mm and a length L2 of 70mm. The drill core sticks 5 are spaced apart from each other across the width W2 of the body 3 by a distance S of approximately 2mm. The two outer drill core sticks 5 are spaced from the edge of the body 3 by the same distance S. The drill core sticks 5 are aligned centrally across the length L2 of the body 3 so that the sectioning faces 19 of the drill core sticks 5 are spaced from the end faces 23 of the body 3 by a distance D of 1mm.

Figure 3 shows a carbon rod 24 placed within the drill core stick 5 located on the right hand side of the sample block 1. The carbon rod 24 has been placed within a void 26 in the drill core stick 5 in order to identify the presence of that void 26, as will be explained in further detail below in reference to the inspection process. A void 26 might be present in the drill core stick 5 as a result of a naturally occurring cavity in the drill core half 71, or because some material has been lost from the drill core half 71.

Figure 4 shows a cross section through the drill core sample block 1 along an axis X-X. The height H of the drill core sample block 1 is 14mm.

The mount plate 11 of the drill core sample block 1 is shown in Figure 5. The mount plate 11 is made from aluminium sheet with a thickness of 5mm. The mount plate 11 is flat and is rectangular with a width W2 and a length L2 that are the same as the length and width of the body 3. One side of the mount plate 11 provides a fixing surface 25 (not shown) that is adhered to the body 3 during manufacture and the opposite side provides a mounting surface 27. The mounting surface 27 is parallel to the inspection surface 9 of the body 3. The mount plate 11 is provided with two attachment apertures 29 that pass through the thickness of the mount plate 11. During manufacture of the drill core sample block 1 the attachment apertures 29 are used to attach the drill core sample block 1 to a tool, for example to a grinder or to a polishing machine. During inspection of the drill core sample block 1, the attachment apertures 29 are used to attach the drill core sample block 1 to an interface plate 31 which enables the drill core sample block 1 to be placed into a scanning electron microscope (as explained in further detail below). The attachment apertures 29 are both offset from the central axis Y-Y of the drill core sample block 1 and to the same side of it, so that the attachment apertures 29 are asymmetrically arranged such that the drill core sample block 1 can be fixed to the interface plate 31 in one orientation only. The attachment apertures 29 are threaded to accept a threaded mechanical fastener (not shown) that can attach the drill core sample block 1 to an interface plate 31 or to a tool. The mount plate 11 is also provided with five circular bonding apertures 33 that pass through the thickness of the mount plate 11. One bonding aperture 33 is located at the centre of the mount plate 11 and one bonding aperture 33 is located towards each of the four corners of the mount plate 11. The bonding apertures 33 assist with bonding of the mount plate 11 to the body 3 during the manufacturing of the drill core sample block 1, as explained below. The mount plate 11 is also provided with a unique identification reference 35.

Figure 6 shows a single drill core sample block 1 attached to a small interface plate 31. Figure 7 shows four drill core sample blocks 1 attached to a large interface plate 31.

Figure 8 shows a sample block mould 151 used in the manufacture of a drill core sample block 1. The sample block mould 151 is made from silicone and is cuboidal, with a cuboidal mould io cavity 153 that is closed by a mould base 155 at a lower end and which is open at an upper end. The mould cavity 153 is dimensioned to produce a drill core sample block 1 with the dimensions set out above. Separating walls 157 extend perpendicularly upwards from the mould base 155 by a height of 2mm. The separating walls 157 are parallel to each other and parallel to the internal walls of the mould cavity 153 and create eight drill core stick slots 159.

Two alignment marks 161 are located on the upper face 163 of the sample block mould 151 and are parallel to and offset from a central transverse axis Y-Y which is located centrally relative to the mould cavity 153 in the same manner as the central transverse axis Y-Y is located centrally relative to the drill core sample block 1. The upper face 163 is also provided with eight drill core stick identification characters 165, each one aligned with a drill core stick slot 159.

A drill core sample block 1 according to the present invention is manufactured in the following way. The first step is to produce the drill core sticks 5 from a length of drill core which has already been cut in half along its longitudinal axis X-X, to produce two drill cores halves 71, each of which has a semi-circular profile in cross-section, as shown in Figure 9. Each drill core half 71 has a diametrical cut face 73 that is flat and has a curved external surface 74. The drill core, and therefore the drill core half 71, typically has a length of approximately 1 metre. The drill core half 71 is placed into a length of aluminium alloy angle profile 281, as shown in Figure 10, which is longer than the drill core half 71, so that the drill core half 71 does not extend past the ends of the angle profile 281. The angle profile 281 has a long side 283 and a short side 285 which are arranged at right angles to each other. The diametrical cut face 73 is located adjacent to the face of the long side 283 and a bottom edge of the diametrical cut face 73 rests against the face of the short side 285. The angle profile 281 is then located so that the long side 283 and the short side 285 are each orientated at 45 degrees to the horizontal, also as shown in Figure 10. Epoxy resin is then poured into the angle profile 281 until it reaches the level F shown in Figure 9. The epoxy resin coats a part of the diametrical cut face 73 and a part of the external surface 74 of the drill core half 71 along the whole length of the drill core half 71 to create the stabilising layer 21. The epoxy resin is left to cure fully before the drill core half 71 is removed from the angle profile 281. The surface of the aluminium alloy of the angle profile 281 is polished (and/or treated with a mould release agent) which enables the drill core half 71 to be readily removed from the angle profile 281.

Once the stabilising layer 21 has cured, the drill core half 71 can be cut to produce the drill core sticks 5, as shown in Figure 11. The drill core half 71 is placed on the bed 283 of a wet rock saw 285 so that the diametrical cut face 73 is adjacent to the bed 283 and so that the curved external surface 74 is abutting a guide rail 287 of the wet rock saw 285. A first thicknessing cut Cl is then made perpendicularly to the diametrical cut face 73 using the wet rock saw 285 to produce a drill core sample strip 75. The thicknessing cut creates the thicknessing face 13 of the final drill core sticks 5.

The first drill core sample strip 75 is then subjected to a further depth cut along the line C2, shown in Figure 12, to produce a primary drill core sample strip 76 and a secondary drill core sample strip 77. The depth cut creates the depth face 15 of the final drill core sticks 5.

Once the primary drill core sample strip 76 and the secondary drill core sample strip 77 have been made, they are each cut into 70mm lengths. Cutting the primary drill core sample strip 76 into lengths creates the drill core sticks 5 which are embedded in the drill core sample block 1. Those drill core sticks 5 have been stabilised as a result of the application of the epoxy resin stabilising layer 21 so that they are less likely to fall apart during subsequent handling steps. Cutting the secondary drill core sample strip 77 into lengths creates a set of partially stabilised drill core sticks 79 which can be utilised for archiving or to provide drill core material for further inspection work.

The next step is to take eight drill core sticks 5 and place them into the sample block mould 151. One drill core sfick 5 is placed into each drill core stick slot 159 and the inspection face 7 (which was the diametrical cut face 73 of the drill core half 71) is placed adjacent to the mould base 155. The drill core sticks 5 are located in the mould cavity 153 of the sample block mould 151 in order, so that the eight drill core sticks 5 are represent of a continuous 560mm length of the drill core half 71 (excepting the parts of the drill core half 71 that were lost when the primary drill core sample strip 76 was cut into the 70mm lengths). The drill core stick identification characters 165 are used to assist with the correct placement of the drill core sticks 5 within the sample block mould 151. Epoxy resin is then poured into the mould cavity 153 to within 3mm of the upper face 163 of the sample block mould 151. The 5mm thick mount plate 11 is then placed into the mould cavity 153 so that its fixing surface 25 is adjacent to the epoxy resin and so that the epoxy resin flows into the bonding apertures 33. The mount plate is orientated so that the attachment apertures 29 are aligned with the alignment marks 161. The epoxy resin is then left to cure.

Once the epoxy resin has cured the drill core sample block 1 is removed from the sample block mould 151. As shown in Figure 13, the face of the drill core sample block 1 that is opposite to the mount plate 11 has a number of channels 91. Those channels 91 need to be removed in order to produce the inspection surface 9 of the body 3 and the inspection face 7 of each drill core stick 5 that is co-planar with a parallel to the inspection surface 9. In order to do this the drill core sample block 1 is fitted to a grinding tool and/or a polishing tool using the attachment apertures 29 on the mount plate 11. The faces of each drill core stick 5 and the epoxy resin of the body 3 are then ground / polished back until the inspection surface 9 and the inspection faces 7 have been produced and the cross-sectional profile of the drill core sample block 1 looks like image of Figure 4.

In order to analyse the drill core sticks 5 that are embedded within a drill core sample block 1, the drill core sample block 1 is attached to an interface plate 31 using screw threaded mechanical fasteners (not shown) that are threaded into the attachment apertures 29 of the mount plate 11. A different interface plate 31 can be used, dependent upon the type of scanning electron microscope, as explained above with reference to Figures 6 and 7. The position of the attachment apertures 29 on the mount plate 11 ensures that the drill core sample block 1 can be placed within the scanning electron microscope in one orientation only.

Once the sample block 1 has been placed within the scanning electron microscope the eight drill core sticks 5 are scanned in order so that data pertaining to a continuous length of drill core can be obtained. For example, looking at the drill core sample block 1 shown in Figure 3, the scanning process can start at the top left-hand corner of the drill core sample block 1 and finish at the bottom right hand corner of the sample block 1. For example, the scanning process can start at the top of the drill core stick 5 on the left hand side of the drill core sample block 1, it can proceed downwardly along that drill core stick 5 until it reaches the bottom of it, and then the next drill core stick 5 can be scanned, again starting from the top and proceeding to the bottom of that drill core stick 5. Figure 3 indicates with dashed lines a central inspection portion 93 of the left-hand drill core stick 5. This central inspection portion 93 is between 3mm and 4mm wide and extends symmetrically to either side of the longitudinal axis X-X. The scanning electron microscope is set up to scan only the central inspection portion 93 of the inspection face 7 of each drill core stick 5. Once all of the eight drill core sticks 5 of the drill core sample block 1 have been scanned the drill core sample block 1 can be removed from the scanning electron microscope and replaced with a new drill core sample block 1 for inspection.

If there is a void 26 in one or more of the drill core sticks 5 then that void will be recognised during the scanning process as a result of the insertion of a carbon rod 24 into the void 26, as explained above and shown in Figure 3. The carbon rod 24 will be clearly recognisable as a part of the sample block 1 that is not a drill core stick 5.

The data collected by the scanning electron microscope can be referenced using the unique identification reference 35 on the drill core sample block 1. As a result the collected data can be cross-referenced to the drill core half 71, so that the petrographic data for any specific point along the length of the drill core half 71 can be retrieved in due course.

Claims

CLAIMS1 A drill core sample block (1) comprising a body (3) within which a plurality of elongate drill core sticks (5) are embedded, wherein each drill core stick (5) has an inspection face (7) that faces outwardly from the body (3) and wherein each drill core stick (5) has been obtained from a drill core.
2. A drill core sample block (1) as claimed in claim 1, wherein the drill core sticks (5) are arranged so that the longitudinal axes X-X of the drill core sticks (5) are parallel.
3. A drill core sample block (1) as claimed in claim 1 or claim 2, wherein the inspection faces (7) of the drill core sticks (5) are parallel to each other.
4. A drill core sample block (1) as claimed in any one of claims 1, 2 or 3, wherein the inspection faces (7) of the drill core sticks (5) are located within a single plane.
5. A drill core sample block (1) as claimed in any of the preceding claims, wherein the drill core sticks (5) are spaced apart from each other.
6. A drill core sample block (1) as claimed in any of the preceding claims, wherein the body (3) is made from an epoxy resin.
7. A drill core sample block (1), as claimed in any of the preceding claims wherein a mounting arrangement (11) is provided on the body (3).
8. A drill core sample block (1) as claimed in claim 7, wherein the mounting arrangement (11) has at least one attachment aperture (29) and wherein the attachment aperture (29) is offset from a central axis Y-Y of the drill core sample block (1).
9. A drill core sample block (1) as claimed in claim 7 or claim 8, wherein the mounting arrangement (11) has at least one bonding aperture (33).
10. A drill core sample block (1) as claimed in any one of claims 7, 8 or 9, wherein the mounting arrangement (11) has a planar mounting surface (27) and the inspection face (7) of each drill core stick (5) is parallel to the mounting surface (27).
11. A drill core sample block (1) as claimed in any one of claims 7 to 10, wherein the mounting arrangement (11) is a mount plate (11).
12. A drill core sample block (1) as claimed in any of the preceding claims, having an inspection surface (9) that is parallel to and co-planar with each of the inspection faces (7)-
13. A drill core sample block (1) as claimed in any of the preceding claims, wherein at least part of the external surface of each drill core stick (5) is provided with a stabilising layer (21).
14. A drill core sample block (1) as claimed in claim 13, wherein the stabilising layer (21) is made of epoxy resin.
15. A drill core sample block (1) as claimed in any of the preceding claims, wherein the drill core sticks (5) represent a continuous length of drill core (71).
16. A drill core sample block (1) as claimed in any of the preceding claims, wherein there are eight drill core sticks (5), each of approximately 70mm in length, representing approximately a 560mm length of drill core.
17. A drill core sample block (1) as claimed in any of the preceding claims, wherein the inspection face (7) of each drill core stick (5) is generally rectangular and is approximately 70mm long parallel to the longitudinal axis X-X and approximately 7mm wide perpendicular to the longitudinal axis X-X.
18. A drill core sample block (1) as claimed in claim 12, wherein the body (3) is cuboidal and the inspection surface (9) is square and has a dimension of up to 150mm x 150mm.
19. A drill core sample block (1) as claimed in any of the preceding claims, having a depth of 14mm.
A method of inspecting a drill core using a drill core sample block (1) as claimed in any of the preceding claims, wherein the drill core sample block (1) is placed into a scanning electron microscope and the scanning electron microscope is used to inspect an inspection face (7) of a drill core stick (5).
21. A method of inspecting a drill core as claimed in claim 20, wherein a central inspection portion (93) of each inspection face (7) is scanned by the scanning electron microscope.
22 A method for producing a drill core stick (5), for a drill core sample block (1), from a drill core sample strip (75), wherein the drill core sample strip (75) is produced by cutting a drill core in half along its length and by making a thicknessing cut (Cl) along one drill core half (71) parallel to the longitudinal axis X-X of the drill core half (71).
23. A method for producing a drill core stick (5) as claimed in claim 22, wherein each drill core stick (5) has an inspection face (7) and the inspection face (7) of each drill core stick (5) is substantially perpendicular to the plane of the cut (Cl).
24. A method for producing a drill core stick (5) as claimed in claim 22 or claim 23, wherein the thicknessing cut (Cl) is substantially perpendicular to the diametrical cut face (73) of the drill core half (71).
25. A method for producing a drill core stick (5) as claimed in any one of claims 22, 23 or 24, wherein a depth cut (C2) is made through the drill core sample strip (75) in a direction perpendicular to the thicknessing cut (Cl).