Abstract
A disconnect sub is connected at one end to a pipe for deployment into a well, where the disconnect sub is then connected to a downhole sealing device such as a plug. The disconnect sub comprises a disconnection point that has a lower tensile break value than the rest of the plug, and has a predetermined tensile break value such that the disconnection point will fail when a threshold value of axial tensile load is applied to the disconnect sub. This offers two methods of disconnection of the pipe from the plug after the plug has set—firstly, rotation of the pipe, or if rotation is not possible, overpull of the pipe in excess of the threshold will cause failure of the disconnection point and separation of the pipe from the plug.
Claims
1. A disconnect sub for releasably connecting a downhole sealing device for deployment in a wellbore of an oil, gas or water well to a pipe string, the disconnect sub comprising: a body with a wall forming a throughbore, the body having axially spaced apart first and second threaded ends, the first threaded end comprising a left-hand thread for connecting to the downhole sealing device and the second threaded end comprising a right-hand thread for connecting to the pipe string; the wall of the body comprising a disconnection point between first and second parts of the wall of the body, and having a lower tensile break value than the rest of the wall of the body, whereby disconnection of the pipe string from the downhole sealing device is achievable by at least one of: clockwise rotation of the pipe string and the disconnect sub relative to the downhole sealing device to disconnect the left-hand thread from the downhole sealing device, and application of an axial tensile load to the disconnect sub equal to or greater than the tensile break value of the disconnection point to separate the first and second parts the wall of the body at the disconnection point.
2. A disconnect sub as claimed in claim 1, wherein the disconnect sub comprises a notch in the wall of the body, wherein the wall of the body has a minimum cross-section at the notch thereby forming the disconnection point.
3. A disconnect sub as claimed in claim 2, wherein the notch is located on the external surface of the disconnect sub.
4. A disconnect sub as claimed in claim 2, wherein the notch is a rounded groove.
5. A disconnect sub as claimed in claim 4, wherein the notch extends one of: around at least a portion of the circumference of the wall of the body; around the majority of the circumference of the wall of the body; and uninterrupted around the whole circumference of the wall of the body.
6. A disconnect sub as claimed in claim 2, wherein the notch is positioned adjacent to the left-hand thread for connecting to the downhole sealing device, wherein the left-hand thread is a shorter male thread for connecting to a longer left-hand female thread of the downhole sealing device, whereby when the shorter male thread is mated to the longer left-hand female thread, the notch is contained within the left-hand female thread of the downhole sealing device to protect the notch from bending loads.
7. A disconnect sub as claimed in claim 1, wherein the disconnection point has a predetermined tensile break value such that the disconnection point will fail when a threshold value of axial tensile load is applied to the disconnect sub.
8. A disconnect sub as claimed in claim 1, wherein the disconnect sub comprises a tapered internal profile.
9. A disconnect sub as claimed in claim 8, wherein the tapered profile is configured to provide a landing profile.
10. A disconnect sub as claimed in claim 1, in combination with a downhole sealing device comprising a plug.
11. A disconnect sub as claimed in claim 1, wherein the disconnect sub comprises: a diverter valve, the diverter valve comprising a set of radially-arranged ports extending through the wall of the body between the throughbore of the disconnect sub and the outer surface of the body; and an axially movable sleeve configured to obstruct the radial ports when in a first configuration to thereby restrict fluid flow between the throughbore and the annulus of the wellbore in use, and to expose the radial ports when in a second configuration, thereby permitting fluid flow between the throughbore and the annulus of the wellbore in use.
12. A disconnect sub as claimed in claim 11, wherein the sleeve comprises seals that straddle the radial ports such that the radial ports are sealed in both an uphole and downhole direction.
13. A disconnect sub as claimed in claim 1, wherein the disconnect sub comprises a diverter valve, the diverter valve comprising: a set of radially-arranged ports extending between the throughbore of the disconnect sub and the outer surface of the body; and an axially movable ball seat, wherein the ball seat comprises a throughbore; wherein in a first configuration of the ball seat, the ball seat obstructs the radial ports, restricting fluid communication between the throughbore of the disconnect sub and the annulus of the wellbore but permitting fluid flow through the throughbore of the disconnect sub in use; and wherein in a second configuration of the ball seat, fluid flow through the throughbore of the disconnect sub is restricted and fluid communication between the throughbore of the disconnect sub and the annulus is permitted in use.
14. A disconnect sub as claimed in claim 13, wherein the ball seat comprises at least one seal, wherein in the first configuration of the ball seat the seal restricts fluid from entering the radial ports.
15. A disconnect sub as claimed in claim 13, in combination with a ball and wherein the ball seat is configured to receive the ball when dropped from surface, wherein the ball acts to block the throughbore of the ball seat, thereby preventing fluid flow through the throughbore of the ball seat and increasing fluid pressure within the throughbore of the pipe.
16. A disconnect sub as claimed in claim 15, wherein the ball seat is configured to actuate from the first configuration into the second configuration when a threshold pressure is reached within the throughbore.
17. A disconnect sub as claimed in claim 13, wherein the ball seat is restrained in the first configuration by one or more separable member(s).
18. A method of disconnection of a pipe string for deployment in a wellbore of an oil, gas, or water well from a downhole sealing device, the method comprising: providing a disconnect sub in accordance with claim 1; connecting the downhole sealing device to the disconnect sub at the first end of the disconnect sub, and connecting the disconnect sub at the second end to the pipe string for running downhole; and disconnecting the pipe string from the downhole sealing device by applying an axial tensile load to the disconnect sub equal to or greater than the tensile break value of the disconnection point.
19. An assembly of a disconnect sub and a downhole sealing device, the disconnect sub for releasably connecting the downhole sealing device for deployment in a wellbore of an oil, gas or water well to a pipe string, the disconnect sub comprising a body with a wall forming a throughbore, the body having axially spaced apart first and second threaded ends, the first threaded end comprising a left-hand male thread for connecting to the downhole sealing device and the second threaded end comprising a right-hand thread for connecting to the pipe string; the wall of the body comprising a disconnection point between first and second parts of the wall of the body, and having a lower tensile break value than the rest of the wall of the body, whereby disconnection of the pipe string from the downhole sealing device is achievable by at least one of: clockwise rotation of the pipe string and the disconnect sub relative to the downhole sealing device to disconnect the left-hand male thread from the downhole sealing device, and application of an axial tensile load to the disconnect sub equal to or greater than the tensile break value of the disconnection point to separate the first and second parts the wall of the body at the disconnection point, the downhole sealing device having a female threaded connector comprising a left-hand female thread for connecting to the left-hand male thread of the disconnect sub, the female threaded connector having an upper end and an internal bore wherein the disconnection point is located adjacent to the left-hand male thread of the disconnect sub, whereby when the left-hand male thread of the disconnect sub is mated to the left-hand female thread of the downhole sealing device, the disconnection point is located below the upper end of the female threaded connector and within the internal bore of the female threaded connector to protect the disconnection point from bending loads.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) In the accompanying drawings:
(2) FIG. 1 shows a schematic side view of an example of a disconnect sub in accordance with the present invention, comprising a rounded groove notch on the external surface of the disconnect sub;
(3) FIG. 2 shows an end view of the disconnect sub of FIG. 1;
(4) FIG. 3 shows a perspective view of the disconnect sub of FIG. 1;
(5) FIG. 4 shows a schematic front view of a plug with the disconnect sub of FIG. 1 in the ‘running in’ position as it is lowered into the wellbore;
(6) FIG. 5 shows a close up schematic sectional front view of the FIG. 4 disconnect sub showing the left-hand thread and notch;
(7) FIG. 6 shows a schematic sectional front view of the FIG. 4 disconnect sub after it has been released from the plug by the preferred method of rotating the drill pipe;
(8) FIG. 7 shows a schematic sectional front view of the FIG. 6 disconnect sub after it has been released from the plug by the alternative method of taking over pull on the drill string and breaking the notch at a predetermined value;
(9) FIG. 8 shows a close up schematic sectional front view of a second embodiment of a disconnect sub in accordance with the invention comprising an internal tapered profile;
(10) FIG. 9 shows a schematic sectional front view of the FIG. 8 disconnect sub after it has been released from the plug by the preferred method of rotating the drill pipe;
(11) FIG. 10 shows a schematic sectional front view of the FIG. 8 disconnect sub after it has been released from the plug by the alternative method of taking over pull on the drill string and breaking the notch at the predetermined value;
(12) FIG. 11 shows a schematic sectional front view of a third embodiment of a disconnect sub in accordance with the present invention, with a diverter valve comprising a ball seat, polymeric seals and shear pins in the ‘running in’ position;
(13) FIG. 12 shows a schematic sectional front view of the FIG. 11 disconnect sub after it has released from the plug via rotation and an activation ball has been dropped and diverted the fluid out the radial ports;
(14) FIG. 13 shows a schematic sectional front view of the FIG. 11 disconnect sub after it has released from the plug via over pull on the drill string and an activation ball has been dropped and diverted the fluid out the radial ports;
(15) FIG. 14a shows a schematic sectional front view of the disconnect sub of FIGS. 1-3 with a notch in the form of an external rounded groove;
(16) FIG. 14b shows a schematic sectional front view of a fourth embodiment of a disconnect sub in accordance with the invention, with a notch in the form of an internal rounded groove;
(17) FIG. 15 shows a close up sectional front view of the FIG. 14a disconnect sub after it has been released from the plug by over pull, with a piece of pipe being obstructed from passage through the bore due to burrs and ragged edges caused by the break;
(18) FIG. 16 shows a schematic sectional front view of a known mechanical setting tool (i.e. not in accordance with the present invention) being pulled to surface via drill pipe from the well bore through wet cement; and
(19) FIG. 17 shows a schematic sectional front view of the slick stinger consisting of the FIG. 4 disconnect sub, coupling and drill pipe being pulled to surface from the wellbore through wet cement.
DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION
(20) FIGS. 1-3 show an example of a disconnect sub 1 in accordance with the present invention comprising a first threaded end 1a, typically a right-hand thread, for connection to the lower end of a drill string (see drill string 4 in FIG. 4) via a coupling if required (see coupling 3 in FIG. 4), and a second threaded end 1b, for connection to the upper end of a bridge plug (see plug 2 in FIG. 4). The disconnect sub 1 comprises a knurled/ridged section 1c around the circumference of the disconnect sub 1, which acts to increase friction and thereby improve grip of tools such as chain tongs that are used to make up the connection of the disconnect sub 1 and the plug 2/drill string 4/coupling 3.
(21) Immediately adjacent to the second threaded end 1b there is a notch 7, in the form of a rounded groove machined into the external surface of the disconnect sub 1, uniformly around the entire circumference thereof, creating a cut-out portion of the wall W of the disconnect sub 1. In other words, the notch 7 is located immediately inbetween the uppermost end, in use, of the second threaded end 1b and the lowermost end, in use, of the uniform outer diameter portion of wall W. The disconnect sub comprises a throughbore T that extends axially through the length of the disconnect sub 1. The disconnect sub 1 wall W is at its thinnest point at the apex A of the notch 7. The second threaded end 1b unusually comprises a left-hand thread 5.
(22) FIG. 4 shows a schematic front view of a first example of a typical plug assembly 50 in the ‘running in’ position comprising a disconnect sub 1, plug 2, coupling 3 and drill pipe 4; in this example, the plug 2 is a bridge plug. In FIG. 4 the plug 2 is connected to the drill pipe 4 (which could be tubing) via the disconnect sub 1 and a coupling 3. The plug assembly 50 is deployed in a wellbore 100. The plug 2 is lowered into the wellbore 100 via drill pipe 4 to the required setting depth. The disconnect sub 1 is coupled to the drill pipe 4 by the coupling 3 via a standard oilfield connection (e.g. box and pin arrangements having a conventional right-hand thread). The disconnect sub 1 is therefore coupled to the plug 2 via the male left-hand thread 5 (e.g. stub ACME or similar) of the second threaded end 1b. The plug 2 incorporates a sealing element which is compressed and retained by a locking mechanism.
(23) FIG. 5 shows a close up sectional front view of the disconnect sub 1 and the left-hand thread 5. The plug 2 has a female left hand thread 6 on its bore which has an opposite hand to the normal thread used to make up the standard oilfield connections. The disconnect sub 1 and the plug 2 are connected by anti-clockwise rotation of the disconnect sub 1, and being disconnected by clockwise rotation. The notch 7 on the disconnect sub 1 is a rounded groove 7 of neck formed on the outer surface of the disconnect sub 1 of the lowermost, in use, end of the wall W, such that the notched portion of the disconnect sub 1 has a smaller outer diameter compared to the major diameter of the sub 1. The notch 7 is positioned above the left-hand thread 5. When the left-hand male thread 5 is made up to the female left hand thread 6, the notch 7 is protected from any bending loads as the length of the male end comprising the left-hand thread 5 is shorter than the female thread 6. The notch 7 is therefore contained within the threaded portion of the plug 2 and thereby protected from premature disconnection caused by loading e.g. side/bending loads.
(24) Once the plug 2 has been set in the wellbore 100, the drill pipe 4 is released. In FIG. 6, the drill pipe 4 is released from the plug 2 by clockwise rotation of the drill pipe 4 at the surface. Using clockwise rotation means that the drill pipe connections, typically right-hand threads, will not loosen. As the connection from the disconnect sub 1 to the plug 2 is a left-hand thread, the drill pipe 4 will release from the plug 2 leaving an open-ended pipe 8.
(25) If rotation of the drill pipe 4 is unsuccessful, the plug 2 can be released by taking an over pull on the drill pipe 4 as seen in FIG. 7. The diameter of the notch 7 has a predetermined tensile break value. The profile of the notch 7 is illustrated as an annular groove, with a rounded profile, but can be shaped differently while still providing a clean break e.g. v-shaped groove. The left-hand threaded portion 5 of the disconnect sub remains in the female thread 6 of the plug. An open-ended pipe 8 is left after disconnecting in a similar manner to FIG. 6.
(26) FIGS. 8-10 show an alternative embodiment of the disconnect sub 1 in the form of disconnect sub 20, which differs from disconnect sub 1 by the inclusion of an internal tapered profile 9. The tapered profile 9 narrows from the nominal internal diameter of the drill pipe 4 to a smaller, predetermined, internal diameter as the taper progresses downwards. The tapered profile 9 can be used as a landing profile for further tools. The tapered profile 9 can also be shaped as a nipple profile. Inclusion of the tapered profile 9 will not impact on the tensile break force as the reduced notch diameter 7 contains the thinnest wall section.
(27) FIG. 9 shows the preferred method of releasing the disconnect sub 20 with the tapered profile 9 from the plug 2 by clockwise rotation of the drill pipe 4, leaving an open ended pipe 8 for further cementing/abandonment operations.
(28) FIG. 10 shows the alternative release method of the disconnect sub 20 taking an overpull on the drill pipe 4. The predetermined tensile break value is exceeded and the disconnect sub 20 breaks at the notch 7, exposing an open ended pipe 8. As the tapered profile 9 is positioned above the left-hand thread 5, disconnecting via this alternative release will result in the tapered profile 9 being exposed and within an open ended pipe 8.
(29) FIGS. 11-13 show a further alternative embodiment of the disconnect sub in the form of disconnect sub 30 which differs from disconnect sub 1 by the inclusion of a diverter valve 25. The diverter valve 25 comprises a ball seat 10, seals 11 and shear pins 12. The disconnect sub 30 comprises radial ports 13, which are sealed by the ball seat 10 and seals 11 above and below the ports 13 when the ball seat 10 is in a first configuration. The ball seat 10 comprises a central aperture 27 that permits fluid to flow through the disconnect sub 30 when the ball seat 10 is in the first configuration.
(30) The preferred method of rotation of the drill pipe 4 releases the disconnect sub 30 from the set plug 2. FIG. 12 shows an activation ball 14 dropped from surface through the drill pipe 4 and landed on the ball seat 10. Pressuring up the fluid from the surface acts to break the set of shear pins 12, permitting axial movement of the ball seat 10 downwards into a second configuration. In this second configuration, the radial ports 13 are exposed. A shoulder 29 extending into the inner diameter of the disconnect sub 30 forms a ‘no go’ 15, which prevents the ball seat 10 from moving further in a down hole direction.
(31) As the radial ports 13 are unsealed, fluid flowing in the throughbore of the drill string 4 is diverted out of the ports 13, and into the wellbore 100.
(32) FIG. 13 shows the alternative release of the disconnect sub 30 comprising the diverter valve 25 from the plug 2 by taking an over pull on the drill pipe 4. Following release of the disconnect sub 30 from the plug 2, an activation ball 14 is dropped after onto the ball seat 10 to move the ball seat 10 into the second configuration as previously described.
(33) FIG. 14a shows a cross-sectional view of the disconnect sub 1 of FIGS. 1-3, with a notch in the form of an annular rounded groove 16 formed or machined in the external surface of the body of the sub 1, which acts to significantly thin the wall of the sub 1 at the notched location. The notched location forms the disconnection point of the sub 1.
(34) FIG. 14b shows a yet further alternative embodiment of the disconnect sub according to the present invention, where the disconnect sub 50 comprises an annular notch 17 formed on the internal surface of the body of the disconnect sub 50, i.e. the surface of the throughbore, or inner diameter, so that the weak portion of the sub 50 formed by the notch 17 is facing inwardly. The notch 17 is illustrated as a rounded groove but can take any suitable shape. Forming the notch 17 on the internal surface of the disconnect sub 50 as shown advantageously improves the cleanliness of the break when the sub 50 is disconnected by the use of overpull, by reducing the likelihood of burrs and/or ragged edges 42 forming on the open lowermost end of the disconnect sub 50. This results in more (or all) of the internal diameter of the remaining portion of the sub 50 being open, which reduces the risk of a tool getting stuck or damaged as it passes through the bore of the sub 1 (see FIG. 15). This example may be particularly useful when running tools through the disconnection point of the sub 50 is planned.
(35) FIG. 15 shows the FIG. 14a disconnect sub 1 with the external rounded groove notch 16 after it has been released from the plug 2 by the alternative method, i.e. taking an overpull on the drill pipe 4. A piece of solid pipe 18 is being obstructed from passage through the bore of the disconnect sub 1 due to unwanted burrs and ragged edges 42 caused by the break of the disconnect sub 1 at the disconnection point. The importance of a clean break allows a full ID bore with no burrs or residual broken material 42 that can obstruct any tools 18 subsequently run through the disconnection point in the inner diameter of the disconnect sub 1, as provided by the internal groove 17 illustrated in FIG. 14b.
(36) FIG. 16 shows a known mechanical setting tool 19 being pulled to surface via drill pipe 4 from the well bore 100 through wet cement in the annulus 20 after the mechanical setting tool 20 has been released from the plug 2. In this scenario the mechanical setting tools' 19 large outer diameter (OD) may cause cement disturbance and channeling to occur as the mechanical setting tool 19 is being pulled to surface through the wet cement 20. This could potentially interfere with cementing operations and lead to remedial work being required, and/or failure of the cement.
(37) FIG. 17 shows an alternative to the tool of FIG. 16 comprising a slick stinger including the disconnect sub 1, coupling 3, and drill pipe 4 being pulled to surface from the wellbore 100 through wet cement in the annulus 20 after the disconnect sub 1 has been released from the plug 2 by the preferred method of rotating the drill pipe 4. In this scenario, the small outer diameter of the slick stinger is much less likely to cause cement disturbance and channeling to occur as the slick stinger is being pulled to surface through the wet cement 20. This example may be particularly useful when used with the disconnect sub 30 comprising a diverter valve 25 and radial ports 13, as the cement may be pumped from the surface into the annulus via the radial ports 13. A reduction in disturbance of the cement after it has been dispensed improves the uniformity of the cement and the cement bond within the wellbore 100.
