AU2017101088B4

AU2017101088B4 - High speed downhole coring system

Info

Publication number: AU2017101088B4
Application number: AU2017101088A
Authority: AU
Inventors: Søren Pham Søe
Original assignee: Minex CRC Ltd
Current assignee: Minex CRC Ltd
Priority date: 2017-08-10
Filing date: 2017-08-10
Publication date: 2020-02-27
Anticipated expiration: 2025-08-10
Also published as: AU2017101088A4

Abstract

Abstract The present invention relates to a downhole coring system. The coring system including a drill rod arranged to form part of a drill string, a drive tube arranged for location within the drill rod, a core barrel located within the drive tube, a drill bit mount for mounting a drill bit and arranged for connection to the drive tube. The drive tube is arranged to be rotated by a down hole turbine motor and the drill rod and drive tube are arranged to each rotate during a coring event.

Description

High Speed Downhole Coring System

Technical Field [0001] The present invention relates to an high speed downhole coring system for taking core samples. The invention has particular application in the oil, gas and mineral industries.

Background of Invention [0002] A core sample is a cylindrical shaped length of material obtained by drilling into a substance such as sediment or rock. Core samples are used to interpret the geological properties of a particular well site. For example, rock and mineral type, porosity, permeability, fluid content, geologic age and probable productivity of oil or gas from the site can all be determined from an analysis of a core sample.

[0003] Taking core samples of an area is an expensive and repetitive process. Accordingly, it is desirable to be able to take the core samples as quickly as possible and in a cost effective manner. One of the ways this is done is by adopting a wireline technique which requires a core barrel to be located within the lower end of the drill string. When the inner tube of the core barrel is full of core, it is removed by attaching an overshot to the spearhead of the landing assembly. The overshot is then pulled through the drill string back towards the ground surface. Accordingly, the core barrel with core attached via the core lifter is retrieved from the well hole without the time consuming removal of each of the rods of the drill string.

[0004] The present invention seeks to provide an arrangement that enables a high penetration rate for the drill bit whilst still being able to recover the core sample in accordance with conventional techniques.

[0005] The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of this application.

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Summary of Invention [0006] According to the present invention there is provided a downhole coring system including a drill rod arranged to form part of a drill string, a drive tube arranged concentrically within the drill rod, a core barrel located within the drive tube, a drill bit mount for mounting a drill bit and arranged for connection to the drive tube, the drive tube being arranged to be rotated by a down hole turbine motor, and the drill rod and drive tube being arranged to each rotate during a coring event, wherein: the turbine motor engages the upper end of the drive tube to establish rotation thereof via a ball and socket arrangement, the ball and socket arrangement allowing for angular misalignment and linear movements between the turbine motor and the drive tube; the drill bit mount is located within a bit mount sub secured to a lower end part of the drill rod, using at least one bearing and at least one seal, held in position by at least one spring means; and a lower end of the drive tube is arranged to engage with an upper part of the drill bit mount, wherein engagement between the drive tube and the drill bit mount enables the drill bit mount to be rotated under the action of the turbine motor for high speed rotation and under the action of the drill rod for low speed rotation; whereby linear movement of the drill bit mount, with respect to the length of the drill string, against the at least one spring means engages the ball and socket arrangement, which enables a bit sharpening event to occur during low speed rotation..

[0007] Accordingly, the present invention provides “dual rotation” of the rod coring system. Such a “dual rotation” of the rod coring system addresses the problem of the low torque of downhole turbine motors. Further, the rotating drill rod reduces friction problems that would otherwise impact on the operation of a drill bit driven by a downhole turbine motor in isolation.

[0008] A clutch arrangement is preferably provided between the drill string and the drill bit mount to enable selective rotation of the drill bit mount only due to rotation of the drill rod during a bit sharpening event.

[0009] In accordance with an embodiment of the invention, the turbine motor is located within the drill string. The turbine motor is preferably arranged within the drill string so as to facilitate positive locating and locking of the turbine motor against axial

2a

2017101088 10 Feb 2020 and rotary forces generated during a normal coring event. Preferably, this is achieved using a latch assembly which includes a latch and a landing ring.

[0010] The turbine motor is also preferably located within the drill string so that throttling of the drill fluid through the turbine motor will signal that the core barrel is full of core.

[0011] The drive tube is preferably located concentrically within the drill rod and will preferably be held in position by a bearing and seal arrangement.

[0012] In accordance with one embodiment of the invention, the turbine motor is arranged to engage to an upper end of the drive tube so as to establish rotation thereof via a ball and socket arrangement. A hexagonal ball and socket arrangement is preferably provided to allow for any angular misalignment and any small linear

2017101088 10 Aug 2017 movements between the turbine motor and drive tube. Other arrangements for establishing rotational drive of the drive tube via the turbine are envisaged.

[0013] A lower end of the drive tube is arranged to engage with an upper part of the drill bit mount. Preferably, this engagement is achieved by way of a spline engagement so as to enable the bit mount to be rotated under the action of the turbine motor for high speed rotation and under the action of the drill rod for low speed rotation during a bit sharpening event. Linear movement of the bit mount with respect to the length of the drill string is preferably provided to enable a bit sharpening event to occur.

[0014] The drill bit mount is preferably located within a bit mount sub that is arranged to be secured to a lower end part of the drill rod. The drill bit mount is preferably positioned within the bit mount sub using at least one bearing and at least one seal which are held in positon by at least one spring means. Such an arrangement enables a lowermost end of the drill bit mount to be extended out of the bit mount sub during a normal drilling event. If the bit requires sharpening, a downward load can be placed on the drill string and hence the drill rod. This load will compress the spring means to stall the turbine motor and to engage drive between the bit mount and the bit mount sub by the drill string. This provides a low speed, high axial load rotation of the drill rod and attached drill bit mount of the type necessary to achieve sharpening in situ of the drill bit.

[0015] The coring system is preferably arranged so that retrieval of a core established within the core barrel is achieved by simply withdrawing a latch assembly with attached turbine motor and core barrel from within the drill string. The latch assembly, turbine motor and core barrel form a single assembly. Other means for retrieving the core barrel are envisaged.

Brief Description of Drawings [0016] An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0017] Figure 1 is a side view of a down hole coring system according to an embodiment of the invention;

2017101088 10 Aug 2017 [0018] Figure 2 is a cross-sectional view of the coring system along the line T shown in Figure 1;

[0019] Figure 3 is a cross-sectional view along the line U-U shown in Figure 2;

[0020] Figure 4 is a cross-sectional view along the line V-V shown in Figure 2;

[0021] Figure 5 is a view similar to Figure 1 but showing sectional line M-M and the rod coring system slightly rotated with respect to Figure 1;

[0022] Figure 6 is a cross-section view along line M-M of Figure 5 and with enlargement circle P marked thereon;

[0023] Figure 7 is an enlarged view of the portion of the coring system marked P as shown in Figure 6;

[0024] Figure 8 is a view similar to Figure 5 but showing sectional line G-G and the coring system slightly rotated with respect to Figure 5;

[0025] Figure 9 is a cross-section view along the line G-G of Figure 8 and with enlargement circle J marked thereon; and [0026] Figure 10 is an enlarged view of the portion of the coring system marked J as shown in Figure 9.

Detailed Description [0027] The following is a description of a preferred embodiment of the invention. Throughout the description terms such as “upper”, “lower”, “upwardly, “downwardly”, “up hole” and “down hole” will be used. It should be understood that these and other similar orientational type descriptive terms are made in relation to the orientation of an operational drill string. For example, the term “upwardly” is used to reflect a direction extending away from the bottom of a drill hole toward ground level. Similarly, the term “downwardly” is used to reflect a direction extending towards the bottom of a drill hole.

[0028] Figures 1,5 and 8 depict a high speed downhole coring system 10 in accordance with an embodiment of the invention at different angular orientations about the rod coring system 10. To facilitate examination of the coring system 10,

2017101088 10 Aug 2017 only a single drill rod 12 is depicted. However, it will be understood that multiple such drill rods 12 forming the drill string will be present when the rod coring system 10 is in use. The number of drill rods 12 will depend on the depth at which the rod coring system 10 is operating below a ground level. The various drill rods 12 forming the drill string rotate during a coring event.

[0029] The coring system further 10 includes a drive tube 14, a core barrel 16, a drill bit mount 18, and a downhole turbine motor 20. The drive tube 14 is arranged during drilling for location within the lowermost drill rod 12. A drill bit 22 is arranged for attachment to the drill bit mount 18. The drill bit 22 is preferably a high speed diamond bit.

[0030] The turbine motor 20 is located within the drill string using a latch assembly and is attached thereto so that the turbine motor 20 is prevented from rotating during drilling. The latch and landing ring of the landing assembly will be configured to prevent such rotation of the turbine motor 20 whilst still allowing the passage of drilling fluids through the turbine motor 20 to provide drive for the drill bit 22 and to also enable normal bit flushing to occur. The Figures illustrate the latch retracting case 25 with latches 27.

[0031 ] The turbine motor 20 provides rotational power to the drill mount 18 via the drive tube 14. The turbine motor 20 is spun by fluid injected down the bore hole which moves past the vanes of the turbine motor 20 which are affixed to a rotor. Rotation of the rotor causes rotation of the drive tube 14. The use of a turbine motor 20 to drive the drill bit 22 is advantageous because the drill bit 22 will be caused to spin much fastener than if a conventional motor drill was used, although there is less torque. The increased spin speed results in the ability to drill faster through harder formations [0032] As best shown in Figure 7, the drive tube 14 is located concentrically within the drill rod 12 and is held in position by bearings 30 and a motor collar 40.

[0033] The turbine motor 20 is arranged to engage with an upper end of the drive tube 14 so as to establish rotation thereof via a ball and socket arrangement 50. An hexagonal ball 52 and a complementary shaped socket 54 are provided to allow for any angular misalignment and any small linear movements between the turbine motor

2017101088 10 Aug 2017 and the drive tube 14. Such an arrangement is also likely to be less susceptible to mud/fines build up that might interfere with re-engagement of the ball 52 of the turbine motor 20 in the socket 54 of the drive tube 14 during return of the core barrel 16 (with attached turbine motor 20) after a core removal event. Other arrangements for establishing rotational drive of the drive tube 14 via the turbine motor 20 are envisaged.

[0034] As shown in Figure 10, a lower end of the drive tube 14 is arranged to engage with an upper part of the drill bit mount 18. Preferably, this engagement is achieved by way of a spline engagement so as to enable the bit mount 18 to be rotated under the action of the turbine motor 20 and to also enable linear movement of the bit mount 18 with respect to the length of the drill string to enable, as will be explained below, a bit sharpening event to occur.

[0035] The drill bit mount 18 is shown located within a bit mount sub 60 that is arranged to be secured to the drill rod 12. The drill bit mount 18 is positioned within the bit mount sub 60 using at least one bearing 62 and at least one seal 64, and at least one spring means 66. A bearing retainer 62a, spring retainer 66a and spring shield 68 are also provided. Such an arrangement enables a lowermost end of the drill bit mount 18 to be extended out of the bit mount sub 60 during a normal coring event. The bit mount sub 60 rotates with the drill rod 12.

[0036] When the bit 22 requires sharpening, a downward load can be placed on the drill string and hence the drill rod 14. This load will compress the spring means 66 to stall the turbine motor 20 and to only engage drive between the bit mount 18 and the bit mount sub 60 by the rotating drill rod 12 (i.e. the rotating drill string). This provides a low speed, high axial load rotation of the drill rod 12 and attached drill bit mount 18 of the type necessary to achieve sharpening in situ of the drill bit 22.

[0037] Figure 10 also illustrates a core of material C being held by a core lifter 16a. A stop ring 16b is also shown. As best shown in Figure 7, a fluid choke shaft 70 is connected to the core barrel 16 by a spring 72 and bearing 74. When the upper end of the fluid choke shaft 70 chokes flow of fluid through the turbine motor 20, it signals the need to bring the core barrel 16 (and attached turbine motor 20) to the

2017101088 10 Aug 2017 ground surface and to extract the core C. A bolt 76, washer 77 and nut 78 are used to secure the fluid choke shaft 70 to the upper end of the core barrel 16.

[0038] The coring system 10 is arranged so that retrieval of the core C established within the core barrel 16 is achieved by simply withdrawing the latch assembly with attached turbine motor 20 and core barrel 16 from within the drill string. The latch retracting case 25 of the latch assembly, the turbine motor 20 and the core barrel 16 form a single retractable assembly.

[0039] The drill rod 12 and drive tube 14 are arranged to each rotate during a coring event. Accordingly, “dual rotation is established by the rod coring system 10. Such a “dual rotation” of the rod coring system 10 addresses the problem of the low torque of downhole turbine motors. Further, the rotating drill rod 12 reduces friction problems that would otherwise impact on the operation of a drill bit 22 driven by a downhole turbine motor 20 in isolation. However, during a bit sharpening event, the turbine motor 20 does not operate and rotation of the drill bit 22 is achieved by rotation of the drill bit mount 18 via the drill rod 12. Thus a low speed, high load rotation of the drill bit 22 can be achieved resulting in sharpening of the bit 22.

[0040] It is envisaged that the described embodiment may introduce vibration issues into the drill string and thus it may be necessary to use high volume drilling fluids between various components of the system 10 to cool them and to also dampen any vibrations.

[0041 ] It is envisaged that a new drill bit will need to be developed to withstand the increased rotational speed envisaged by embodiments of the invention. For example, it is envisaged that the drill bit will rotate at speeds of about 4500 rpm in order to achieve a penetration rate of 560mm/min. This compares to conventional systems using a HQ drill bit which rotate at between about 800 and 1350 rpm, with a penetration rate of about 125mm/min. This would provide a productivity gain of about 4.5 times as compared to the rate of penetration of a conventional system.

[0042] The embodiments have been described by way of example only and modifications within the spirit and scope of the invention are envisaged.

2017101088 10 Aug 2017 [0043] Future patent applications may be filed in Australia or overseas on the basis of or claiming priority from the present application. It is to be understood that the following claims are provided by way of example only, and are not intended to limit the scope of what may be claimed in any such future applications. Features may be added to or omitted from the claims at a later date so as to further define or redefine the invention or inventions.

Claims

The claims defining the invention are as follows:

1. A downhole coring system including a drill rod arranged to form part of a drill string, a drive tube arranged concentrically within the drill rod, a core barrel located within the drive tube, a drill bit mount for mounting a drill bit and arranged for connection to the drive tube, the drive tube being arranged to be rotated by a down hole turbine motor, and the drill rod and drive tube being arranged to each rotate during a coring event, wherein:

a) the turbine motor engages the upper end of the drive tube to establish rotation thereof via a ball and socket arrangement, the ball and socket arrangement allowing for angular misalignment and linear movements between the turbine motor and the drive tube;

b) the drill bit mount is located within a bit mount sub secured to a lower end part of the drill rod, using at least one bearing and at least one seal, held in position by at least one spring means;

c) and a lower end of the drive tube is arranged to engage with an upper part of the drill bit mount, wherein engagement between the drive tube and the drill bit mount enables the drill bit mount to be rotated under the action of the turbine motor for high speed rotation and under the action of the drill rod for low speed rotation; whereby linear movement of the drill bit mount, with respect to the length of the drill string, against the at least one spring means engages the ball and socket arrangement, which enables a bit sharpening event to occur during low speed rotation.
2. A downhole coring system according to claim 1 further including a clutch arrangement to enable selective rotation of the drill bit mount only due to rotation of the drill rod.
3. A downhole coring system according to claim 2 wherein the clutch arrangement is provided between the drill string and the drill bit mount
4. A downhole coring system according to any one of claims 1 to 3, configured so that retrieval of a core established within the core barrel is achieved by withdrawing the turbine motor and attached core barrel from within the drill string.

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5. A coring system according to any one of claims 1 to 4, wherein engagement between the drive tube and the drill bit mount is achieved by way of a spline engagement.