Colliding tool

Abstract

A colliding tool for severing a target in a wellbore as described. The tool comprises a housing having a first chamber, the first chamber containing an explosive charge; and an at least one detonator connected to the explosive charge, the at least one detonator being insulated from temperature in the wellbore. In use, the at least one detonator is configured to simultaneously initiate a first explosion at a first end of the explosive charge and a second explosion at a second end of said explosive charge.

Claims

1. A colliding tool for severing a target in a wellbore, the tool comprising: a housing having a first chamber, the first chamber containing an explosive charge; an at least one detonator connected to the explosive charge, the at least one detonator being insulated from temperature in the wellbore by a thermally insulated device; and a signal path including an electrical signal path, the signal path permitting a signal to pass through at least a portion of the tool to the at least one detonator, a metallic housing or container of the thermally insulated device forming part of the electrical signal path to the detonator; wherein, in use, the at least one detonator is configured to simultaneously initiate a first explosion at a first end of the explosive charge and a second explosion at a second end of said explosive charge.

2. The colliding tool of claim 1, wherein the at least one detonator is a single detonator.

3. The colliding tool of claim 2, wherein, where there is a single detonator, the detonator is connected to opposite ends of the explosive charge by two separate strands of a detonating cord of equal length.

4. The colliding tool of claim 2, wherein, where there is a single detonator, the detonator is connected to opposite ends of the explosive charge by a strand of detonating cord which bifurcates into two strands of detonating cord of equal length.

5. The colliding tool of claim 1 wherein the at least one detonator is positioned closer to one end of the explosive charge than the other.

6. The colliding tool of claim 5, wherein a strand of detonating cord connected to a proximal end of the explosive charge is coiled.

7. The colliding tool of claim 5, wherein a strand of detonating cord is wound around a mandrel.

8. The colliding tool of claim 1, wherein the tool further comprises a second chamber for housing the at least one detonator, the first and second chambers being connected by a bridging piece.

9. The colliding tool of claim 8, wherein each chamber defines an angled face, the angled face abutting a complementary angled face defined by the bridging piece.

10. The colliding tool of claim 1, wherein the first chamber comprises a thin walled high yield steel.

11. The colliding tool of claim 10, wherein the tool further comprises a second chamber for housing the at least one detonator, the first and second chambers being connected by a bridging piece, wherein the second chamber comprises a thin walled high yield steel.

12. The colliding tool of claim 1, wherein the at least one detonator is stored within the thermally insulated device.

13. The colliding tool of claim 12, wherein the thermally insulated device comprises a vacuum flask located within the metallic housing or container.

14. The colliding tool of claim 1, wherein the tool housing forms part or all of the thermally insulated device.

15. The colliding tool of claim 1, wherein the thermally insulated device comprises a temperature insulating material selected from a graphene, a foam, and an aerogel.

16. The colliding tool of claim 1, wherein the thermally insulated device is electrically isolated from the colliding tool housing to prevent a short circuit with the tool housing.

17. The colliding tool of claim 1, wherein the thermally insulated device is attached to the tool housing by a mounting.

18. The colliding tool of claim 17, wherein the mounting comprises a high temperature insulating material.

19. The colliding tool of claim 17, wherein the mounting forms part of the signal circuit path, the detonation signal being passed through the mounting to the thermally insulated device.

20. The colliding tool of claim 1, wherein the colliding tool comprises a shock attenuating mandrel.

21. The colliding tool of claim 20, wherein the shock attenuating mandrel comprises a concertina shaped tubular section.

22. The colliding tool of claim 20, wherein the shock attenuating mandrel comprises a deformable elastomer.

23. The colliding tool of claim 20, wherein the shock attenuating mandrel comprises a spring.

24. The colliding tool of claim 1, wherein the first chamber is defined by a housing wall.

25. The colliding tool of claim 24, wherein the housing wall includes a thinned portion.

26. The colliding tool of claim 25, wherein the thinned portion is a circumferential groove.

27. The colliding tool of claim 26, wherein the circumferential groove is machined on the internal surface of the first chamber.

28. The colliding tool of claim 1, wherein the explosive charge is a propellant.

29. The colliding tool of claim 1, wherein the colliding tool comprises sensing equipment to locate a feature or an obstacle which could impact positively or negatively on the severance of the target.

30. The colliding tool of claim 29, wherein the sensing equipment includes pulse eddy current generators or generators of magnetic fields.

31. A method of severing a target in a wellbore, the method comprising: disposing a tool adjacent a target to be severed in a wellbore, the tool having a housing, the housing having a first chamber, the first chamber containing an explosive charge, and an at least one detonator connected to the explosive charge, the at least one detonator being insulated from temperature in the wellbore by a thermally insulated device; transmitting a signal along a signal path including an electrical signal path, the signal path permitting a signal to pass through at least a portion of the tool to the at least one detonator, a metallic housing or container of the thermally insulated device forming part of the electrical signal path to the detonator; and simultaneously detonating a first explosion at a first end of the explosive charge and a second explosion at a second end of the explosive charge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a section of a colliding tool according to an embodiment of the present invention.

(3) FIG. 2 is a detailed view of the bridging piece of the embodiment shown in FIG. 1.

(4) FIG. 3 is a detailed view of the end cap of the embodiment shown in FIG. 1.

(5) FIG. 4 is a detailed view of the connection of the detonator vacuum flask of the embodiment shown in FIG. 1.

(6) FIG. 5 is a detailed view of the circuit that follows an electrical detonating signal when the colliding tool is in use.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) Referring first to FIG. 1, a section of a colliding tool, generally indicated by reference numeral 1, is shown, according to an embodiment of the present invention. The colliding tool 1 comprises a first chamber 4, which is an explosives chamber 8 that contains an explosive charge 5, a second or detonator chamber 2 that contains a vacuum flask 10 housing a detonator 64. The vacuum flask 10 is within a metallic casing 62, wrapped with electrically insulating tape in order to insulate it from the second chamber 2. By placing the vacuum flask 10 within the metallic casing 62, the vacuum flask 10 is protected against the high-pressure environments found in deep oil wells, particularly in HPHT wells. The metallic casing 62 provides mechanical support and strength to the vacuum flask 10 and prevents the flask 10 being broken or shattered within the second chamber 2. The metallic casing 62 is wrapped with temperature-resistant electrically insulating tape such as Kapton tape.

(8) The colliding tool 1 further comprises a bridging piece 3 connecting the first chamber 4 and the second chamber 2, and a concertina shaped shock attenuating mandrel 6 located above the second chamber 2.

(9) Referring now to FIG. 2 some constructional features of the colliding tool 1 according to the present invention will be described. FIG. 2 represents the bridging piece 3 of FIG. 1 and shows how it is connected to the chambers 2, 4.

(10) The second chamber 2 fits onto a bridging piece recess 21. The bridging piece recess 21 defines two circumferential grooves 22, 23, each groove accommodating an O-ring 24 and an anti-extrusion ring 25.

(11) The bridging piece recess 21 further defines a threaded hole 26 which receives a hexagonal socket head cap screw 27 which passes through a hole 28 in the wall of the second chamber 2, connecting and securing the second chamber 2 to the bridging piece 3. One or more such threaded connections may be used to secure the second section 2 to the bridging piece 3.

(12) The interface 29 between the second chamber 2 and the bridging piece 3 is angled at 10 from a perpendicular to the tool longitudinal axis. This interface arrangement captures the end of the second chamber 2, preventing the end of the second chamber 2 splaying out during detonation. An identical connection is made between the bridging piece 3 and the first chamber 4, and the first chamber 4 and a tool end cap 7.

(13) The bridging piece 3 also comprises a port 30 to receive a bleeder valve assembly (not shown). The purpose of this bleeder valve assembly is to allow any trapped pressure in the tool to be safely relieved, should a pressure relief plug (discussed in due course in connection with FIG. 3) malfunction or not be used (by designing and manufacturing an end cap 7 with no pressure relief plug 9).

(14) Referring now to FIG. 3 additional constructional features of the colliding tool 1 according to the present invention will be described. The end cap 7 has an exterior recess 31 that fits into an interior recess 32 of the first chamber 4. The end cap 7 has two circumferential grooves 33, 34 on the recessed portion. Each groove 33, 34 accommodates an O-ring 43 and an anti-extrusion ring 44.

(15) The end cap interior recess 32 further defines a threaded hole 35 that receives a hexagonal socket head cap screw 36 which passes through a hole 37 in the wall of the first chamber 4, connecting and securing the first chamber 4 to the end cap 7. One or more such threaded connections may be used to secure first chamber 4 to end cap 7.

(16) The end cap 7 has a longitudinal hole 38 that connects the explosives chamber 8 (the first chamber 4) with the exterior of the colliding tool 1 for receiving a pressure relief plug 9. The pressure relief plug 9 has two circumferential grooves 39, 40 on its side and has been phosphate coated before assembling. Each groove accommodates an O-ring 45 and an anti-extrusion ring 46.

(17) In use, the first chamber 4 may be held at atmospheric pressure. When the colliding tool 1 is deployed into a well, the pressure outside the colliding tool 1 is greater than the pressure inside the first chamber 4 and this pressure difference keeps the pressure relief plug 9 in place.

(18) In the event that failure of the colliding tool 1 results in a pressurised situation within the first chamber 4, the colliding tool 1 must be slowly lifted and when the colliding tool 1 reaches a position in the well where the pressure is lower than the pressure within the first chamber 4, the pressure relief plug 9 will open and relieve the pressure inside the first chamber 4, until the pressure within the first chamber 4 is in equilibrium with the environmental pressure.

(19) The compression spring 42, which is used to compress the explosive charge 5 is also visible in FIG. 3.

(20) The colliding tool 1 of the above-described embodiment is capable of withstanding well pressures of 25,000 psi (172,368,932 Pa) and temperatures of 450 to 500 F. (232 to 260 C.) and is therefore suitable to be used in the so-called high pressure-high-temperature wells and therefore can be considered a HPHT colliding tool 1.

(21) Referring to FIG. 4, the end of the second chamber 2 opposite the bridging piece 3 is shown. This part of the colliding tool 1 includes a mounting 51 at one end of the metallic casing 62, which is insulated from the second chamber 4 by a surrounding layer of electrically insulating tape (not visible). By wrapping the metallic casing 62 with a temperature-resistant electrically insulating tape, as will be described, a detonating signal may be transmitted through the metallic casing 62 without being transmitted or lost to adjacent colliding tool parts and the temperature-resistant electrically insulating tape will not melt at the temperatures found in HPHT wells.

(22) The mounting 51 is a plastic cup made of PEEK (Polyether-ether-ketone, a high temperature resistant insulating material), attached to an electric spring contact 52, which is supported on a contact plate 53 made of 316 stainless steel. The tool 1 is connected to surface by a first cable 61 (see FIG. 5), which, in turn, is connected to the contact plate 53.

(23) Referring now to FIG. 1, FIG. 2, FIG. 4 and FIG. 5, the operation of the colliding tool 1 will now be described.

(24) In operation, a positive electrical signal from surface passes to the contact plate 53 through the first cable 61. The signal is then passed to the metallic casing 62 through the contact plate 53. The advantage of transmitting the electrical detonation signal through the metallic casing 62 is that there is no need to use cables in the chamber 2 that houses the metallic housing and this is an advantage because the internal space available within the colliding tool 1 is restricted by the diameter of the colliding tool 1 which is constrained by the pressure it must withstand and the internal diameter of the wellbore and/or wellbore restriction it needs to pass through.

(25) At the mouth of the metallic casing 62 (FIG. 5), a second cable 63 receives the positive signal and transmits it to the detonator 64, which is stored within the vacuum flask 10. It will be noted there is a sleeve 54 (see FIG. 2) over the vacuum flask mouth to insulate this part of the vacuum flask 10 from the second chamber 2 to prevent a short circuit.

(26) The detonator 64 is fired and the explosive output from the detonator 64 is transferred by a detonating cord 65 through a hole 55 (FIG. 2) in the bridging piece 3 towards the first chamber 4 containing the explosive charge 5.

(27) At the end of the bridging piece 3 nearest to the first chamber 4, the detonating cord 65 splits into two strands of equal length (not shown). One strand is connected to the furthest end of the explosive charge 5 and the other is connected to the nearest end of the explosive charge 5. The strand of detonating cord 65 connected to the end of the explosive charge 5 closest the bridging piece 3 is coiled or wound around a mandrel 56 so that it takes less space within the colliding tool 1.

(28) The explosive charge 5 detonates and the shockwave created at each end travels through the column of explosive charge 5 until the shockwaves meet in the middle where a perpendicular shockwave may be emitted from the colliding tool 1 to sever the stuck pipe.

(29) When the explosions take place, energy is absorbed by a controlled deformation of the shock attenuating mandrel that collapses and forms a shorter mandrel, thereby absorbing an important part of the explosions' energy and preventing or reducing its transmission through the tubular string upwards, which otherwise might be dangerous and harmful to other equipment located above the colliding tool 1.

(30) The present invention provides a colliding tool 1 useful for severing stuck drill string or other stuck downhole parts in HPHT wells. The colliding tool 1 comprises improved safety features like a single detonator, a pressure relief plug and separated compartments for the detonator and explosive charge. Simultaneous explosions at opposite ends of the explosive charge are achieved by using strands of detonating cord of equal length.

(31) Various modifications may be made within the scope of the invention as herein described, and embodiments of the invention may include combinations of features other than those expressly described.

(32) For example, in alternative embodiments, the detonator may fire a single strand of detonating cord that may be divided in two strands of equal length when the detonating cord enters the explosives chamber. In further alternatives, there may be multiple separate detonators.

(33) Further, although the plastic cup is described as being made of PEEK any suitable high-temperature insulating material may be used.

(34) The tool may be phosphate coated. This enhances the resistance against corrosion of the colliding tool.