"CORE ORIENTATION APPARATUS

Technical Field

[0001 ] The present invention relates to a core orientation apparatus. Background Art

[0002] Core samples are obtained through core drilling operations. Core drilling is typically conducted with a core drill comprising inner and outer tube assemblies. A cutting head is backed up by a cylindrical core barrel that is pressed against the subject materials. The cutting head is then rotated at speed and constant pressure applied to cut out a core sample, a cylinder of the subject material for geological testing. The lengths of samples can range from less than a meter to around 100 meters in one run.

[0003] Once a core sample of sufficient length is generated, the core sample is broken away from the surrounding rock and then bought to the surface along with the core sample storage device so that it may be studied'.

[0004] Typically core drilling operations are performed at an angle to the vertical and it is desirable to have an indication of the orientation of the core sample relative to the underground environment from which it was extracted.

[0005] It is a well known practice to mark the relative orientation of the core sample with respect to the low side of the drill hole via the use of a spear or a pencil, wherein the core is marked with a scribe that falls down the bore hole marking the low side of the core.

[0006] Once the core is removed this is then transcribed to the high side of the core sample. In this manner the 'high side' of the core is commonly marked so that the relative orientation of the core, relative to surface can be determined. [0007] As will be appreciated by those skilled in the art, determining the relative orientation of the core sample in respect to the gravity vector affords a geologist a better understanding of the formation of minerals in the drilling area. Other core orientation systems have been designed to increase the available information regarding the relative orientation of the core sample prior to breaking.

[0008] Whilst it is the aim of the drilling operation to produce a hole that is straight, it is common for deviations in the azimuth and pitch of the hole to occur. These deviations cause errors in the determination of the orientation of the core sample relative to its original environment.

[0009] Previous examples of core orientation devices have lacked the ability to determine the azimuth orientation of the core as it removed from the ground and therefore are unable to determine the true orientation of the core relative to its underground environment prior to it having been bought to the surface.

[0010] Previously two systems have been required to orientate the core and to determine the time orientation of the core; low side orientation and borehole deviation. Previous examples of core orientation devices have used MEMS systems to determine the azimuth orientation of the core. However, such devices are not autonomous and rely on a reference direction and measure inertia from one station to another. That is existing MEMS systems require at least two devices to determine a relative direction.

[0011 ] The present invention attempts to overcome at least in part the aforementioned disadvantages of previous core orientation apparatus.

Summary of the Invention

[0012] In accordance with one aspect of the present invention there is provided a core sample orientation system for determining the relative orientation of a core sample with respect to its surrounding prior to removal from a bore hole, the system comprising an alignment device and a display device, the alignment device being arranged to engage with a core barrel, the alignment device comprising a protective shroud, at least one sensing means and control electronics, the sensing means comprising at least one set of mutually orthogonal gyroscopes, characterized in that the sensing means is capable of determining the relative orientation of the alignment device with respect to true north and the relative orientation of a core sample within the core barrel and the control electronics are configured to transmit relative orientation information to the display device.

[0013] Preferably, the mutually orthogonal gyroscopes comprise micro-electronic mechanical systems (MEMS) gyroscopes.

[0014] More preferably, the mutually orthogonally opposed gyroscopes comprise a fibre- optic gyroscope.

[0015] Preferably, the alignment device is arranged to be attached to the core barrel whilst drilling is being undertaken.

[0016] More preferably, the alignment device is arranged as part of a spear to be dropped down the bore hole to engage a core barrel.

[0017] Alternatively, the alignment device is arranged to engage a core barrel after a core has been removed from the bore hole and the core barrel is being returned to the bore hole.

[0018] Preferably, the control electronics are configured to reduce or remove signal noise in the signals generated by the gyroscopes.

[0019] Preferably, the control electronics are configured to control pulse width modulation of the laser used in the fibre-optic gyroscope.

[0020] Preferably, the control electronics are configured to wirelessly transmit orientation information to the display device. [0021] Preferably, the control electronics are configured to transmit orientation information to a RFID scanning device, the scanning device being configured to write the orientation information to a RFID tag which is physically associated with the core sample.

[0022] Preferably, the RFID tag comprises a mark for indicating the relative orientation of the core sample to which it is attached.

Brief Description of Drawings

[0023 ] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is an alignment device in accordance with the present invention.

Best Mode for Carrying out the Invention

[0024] Referring to the Figures, there is shown a core orientation apparatus comprising an alignment device 10. The alignment device 10 is preferably arranged to engage with a core barrel 12. The alignment device 10 further comprises an outer casing of impact resistant material to protect the internal components of the alignment device 10. The alignment device 10 preferably comprises at least one set of mutually orthogonal gyroscopes.

[0025] The mutually orthogonal gyroscope are arranged to enable the alignment device 10 to determine the device's relative orientation to true north, thereby allowing the relative azimuth of the device to be determined. This allows the true orientation of the device relative to the drill hole to be determined as well as the relative angle of the device and the drill head to which it is attached.

[0026] Preferably, the mutually orthogonal aligned gyroscopes used in the alignment device 10 are Micro Electrical Mechanical System (MEMS) devices which are autonomously north seeking. Although MEMS devices are preferably used the alignment device 10 may use any suitable gyroscope such as a fibre-optic gyroscope (FOG).

[0027] The alignment device preferably comprises electrical control equipment to allow the alignment device to determine the true north bearing from its present location. MEMS based gyroscopes often suffer limitations due to the large amount of signal noise generated by their operation, with this noise effectively causing 'drift' in the readings generated. The control electronics are capable of running a proprietary algorithm which reduces the signal noise and 'drift'.

[0028] A surface computer is used to synchronise time between the alignment device and a computer. Depth can be manually entered into the surface computer or fed into the computer via a depth encoder device such as an optical depth encoder or non contact sensors.

[0029] Preferably, the alignment device further comprises a means of transmitting the orientation information such as via a wireless or Bluetooth connection. Alternatively, the alignment device may be connected to equipment on the surface via a cable which is disposed within the inner tube assemblies.

[0030] In use, as the drilling operation progresses a core sample is produced, it is gripped by a core barrel 12, with the alignment device 10 being arranged to engage the core barrel. Preferably, the alignment device 10 is located as far away from the cutting head 14 attached to the core barrel 12 as practicable.

[0031] Once a core sample of sufficient size is generated and gripped within the core barrel, the drilling assembly will be bought to rest and the alignment device 10 will determine the orientation of the drilling assembly relative to true north.

[0032] Core orientation as well as azimuth and dip readings may be taken at regular intervals as the core barrel is filled and prior to breaking off the core sample for retrieval to the surface. [0033] Once the orientation of the alignment device 10 and therefore the core sample 16 is determined, the core barrel 12 is bought to the surface by a spear engaging with a core barrel lifter 18 or overshot.

[0034] On the way to the surface it is possible for the core barrel 12 and alignment device 10 to be stopped at a number of points to allow the modelling of the drill hole and the actual path of travel of the drill hole.

[0035] Once at the surface, the core sample orientation information captured by the alignment device 10 prior to removal of the core sample 16 from the drill hole is used to allow the core to be rotated such that the orientation of the alignment device 10 relative to the low side of the drill hole is the same as when the alignment device 10 was in the drill hole. The core sample 16 may then be marked to demonstrate its relative orientation to the drill hole. The additional information relating to the core samples orientation is then passed into a computerised database for later use.

[0036] In accordance with another aspect of the present invention, the orientation data generated by the alignment device may be written to a Radio Frequency Identification (RFID) device and associated with the sample. The RFID device may be written to and read in a known manner, allowing the data associated with a specific sample to be read when required once the sample has moved away from the drill hole.

[0037] The actual orientation of the RFID tag may be used to mark or demonstrate the orientation of the core sample 16 in the ground. The RFID tag used may have a marking to indicate orientation relative to the ground when attached to an end portion of the core sample 16.

[0038] In accordance with an alternative embodiment of the present invention the alignment device 10 is accommodated within a protective shroud and is fed down the drill hole after the core barrel has been removed from the drilling assembly. Once the /

alignment device is in the distal portion of the drilling hole, it is allowed to rest and determine the orientation of the drill hole relative to true north.

[0039] Preferably, the orientation information generated by the alignment device 10 is then transmitted to the surface either through a cable which may also be the tether for the alignment device 10 or is transmitted wirelessly once the device 10 is at the surface of the drill hole.

[0040] In accordance with another preferred embodiment of the present invention, the alignment device 10 is arranged to comprise part of the spear or overshot, which is fed down the bore hole to retrieve the sample. Once the spear or overshot has engaged with the barrel, the alignment device 10 then determines the relative orientation of the core prior to removal.

[0041 ] Preferably, the orientation information generated by the alignment device 10 is then transmitted to the surface either through a cable which may also be the tether for the alignment device 10 or is transmitted wirelessly once the device 10 is at the surface of the drill hole.

[0042] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.