BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates generally to systems and methods for severing a tube- wire or similar transmission conductor that is disposed in a surrounding tubular.

2, Description of the Related Art

[0002] Coiied tubing has become a popular means for running a bottom hole assembly ("BHA") into a subterranean weilbore. A wireline or tube-wire is sometimes run inside of the coiled tubing when realtime downhole data is required, such as during directional drilling or logging. Tube-wire is a tube that contains an insulated cabie that is used to provide eiectrical power and/or data to the bottom hole assembly or to transmit data from the BHA to th surface. Tube-wire is available commercially from manufacturers such as Canada Tech Corporation of Caigary, Canada.

[0003] in the event that coiled tubing and the associated BHA become stuck in the weilbore, it is common practice to pump a ball or plug down through the coiled tubing in order to disconnect the BHA from the coiled tubing, if this fails to free the coiied tubing, then the contingency is to kill the well, cut the coiled tubing at the surface, and run a chemical cutter on wireline down through the coiied tubing in order to retri eve the coiied tubing from th weil. if this problem occurs with TeleCoil, then it is necessary to retrieve the tube-wire before running the chemical cutter. The tube-wire in a TeleCoii string is comparativeiy weak compared to conventional braided cable, and using a tensile shear release mechanism in the BHA for the tube-wire is considered unreliable. Accordingly, the TeleCoil BHA incorporates a baii operated tube-wire release mechanism to facilitate retrieval of the tube-wire. There is no contingency available in the event of a failure of this mechanism. Conventional drop bars and "go devil" devices that are used to sever s!ickline rely upon gravity to be delivered to a point wherein they can sever the sliekiine. They are unsuitable for use in horizontal or deviated we!lbores.

SUMMARY OF THE NVENTION

[0004] The invention provides devices and methods for severing a tube-wire proximate the BHA of a coiled tubing run BHA. The devices and methods described are useful in the event that the coiled tubing becomes stuck within the surrounding wellbore. An exemplary shear pig assembly is described that radially surrounds the tube-wire and is axiaS!y moveable along it. The exemplary shear pig assembly includes a main body portion and a nose. The nose may be affixed to the main body portion by a frangible connector, A shear chamber is formed between the main body portion and the nose, and a shear piug is disposed within the shear chamber. The exemplary shear pig assembly also includes a fin array that radially surrounds a shaft of the main body portion to help propel the shear pig assembly through the flowbore of the running string,

[0005] To actuate the shear pig assembly to sever the tube-wire, the shear pig assembly is moved downwardly along the tube-wire to a predetermined location wherein it is desired to sever the tube-wire. When the shear pig assembly reaches this point, the nose of the cutting assembly encounters a contact fitting within the running string which stops the downward movement of the shear pig assembly. The shear pig assembly is preferably so moved by pumping fluid into the coiled tubing running string at the surface. In particular embodiments, the shear pig assembly has a relatively short axial length that will permit it to negotiate coiled tubing that is wrapped around a reel at the surface. When the nose of the shear pig assembly contacts the contact fitting, the frangible connector is ruptured. The main body of the shear pig assembly is moved axia!iy toward the nose causing the shear chamber to collapse axia!iy. This collapse causes the shear p!ug to move radially within the shear chamber. In this embodiment, the tube- wire is severed between the shear plug and the nose as well as between the shear plug and the main body. Once severed, the tube-wire can be withdrawn from the running string,

BRIEF DESCRIPTION OF THE DRAWINGS

[000S] The advantages and further aspects of the invention wi!i be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or simiiar elements throughout the several figures of the drawing and wherein;

[0007] Figure 1 is a side, cross-sectional view of an exemplary weilbore having a BHA being run in with coiled tubing and tube-wire.

[0008] Figure 2 is a side, cross-sectional view of an exemplary shear pig assembly constructed in accordance with the present invention and shown within the coiled tubing string and surrounding the tube-wire.

[0009] Figure 3 is a side, cross-sectional view of the shear pig assembly of Figure 2, now having been actuated to sever the tube-wire.

[0010] Figure 4 is a schematic, side view, partially in cross-section depicting a shear pig assembly in accordance with the present invention being pumped through coiled tubing on a reel,

[0011] Figure 5 is a further view of the coiled tubing reel shown in Figure 4 apart from other components.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [00 2] Figure 1 illustrates and exemplary wel!bore 0 that has been drilled through the earth 12 from the surface 14. A bottom hole assembly (or BHA) 16 is affixed to a coiled tubing running siring 18. The BHA 18 includes a mud motor 17, an electronics sub 19, and a milling bit 20 that is used to dear debris from the weiibore 10. An interior flowbore s 22 is defined along the length of the running siring 18, and tube-wire 24 is disposed within the flowbore 22 and is interconnected with the BHA 16 in a manner known in the art. An annular contact fitting 25 is located within the flowbore 22 just above the BHA 18,

[0013] An exemplary shear pig assembly 26, which has been constructed ino accordance with the present invention, is shown radially surrounding the tube-wire 24 within the running string 18. The shear pig assembly 26 is axiaily moveabie along the tube-wire 24 and is preferably propelled downwardly through the flowbore 22 of the running string 18 by fluid pressure, as will be described in further detail shortly.

[0014] The exemplary shear pig assembly 26 is shown in greater detail in Figures 2 s and 3. The shear pig assembly 26 includes a main body 28 and a separate nose 30.

The main body 28 has a central shaft 32 with a central axial passage 34 disposed along its length. An annular fluid seal 35 is provided between the shaft 32 and the tube-wire 24. In the depicted embodiment, the distal end 36 of the shaft 32 presents an angled face 38. The proximal end 40 of the shaft 32 preferably presents an enlarged diameter0 portion 42. In certain embodiments, an annular flange 44 projects radially outwardly from the shaft 32.

[00 5] Also in particular embodiments, an annular fin array 46 radially surrounds the shaft 32 between the enlarged diameter portion 42 and the flange 44. The fin array 46 preferably includes a plurality of angled fins 48 or cups that are shaped to receive and5 contain fluid pumped from the surface 14. In particular embodiments, the fin array 46 Is formed of polyurethane or a similar resilient material, in preferred embodiments, the fins 48 of the fin array 48 extend radia!iy outwardly to contact the surrounding running string 18.

[00 6] The nose 30 of the pig assembly 26 radially surrounds the distal end 38 of the shaft 32. An o-ring fluid seal 50 provides a fluid seal between the nose 30 and the shaft 32. A frangible connector in the form of a shear pin 52 preferably secures the nose 30 to the shaft 32. The nose 30 also preferably presents a distal end 54 having an annular angled surface portion 56.

[00 7] A generally wedge-shaped shearing chamber 58 is defined axiai!y between the nose 30 and the shaft 32. The shearing chamber 58 is wedge-shaped due to the presence of the angled face 38 of the shaft 32 and an oppositely-angled interior face 60 that is presented by the nose 30.

[00 8] A shear plug 62 is retained within the shearing chamber 58. The shear plug 62 is generally cylindricai with a first angled surface 64 that is complimentary to the a gled face 38 of the shaft 32 and a second angled surface 66 that is complimentary to the angled face 60 of the nose 30, A central passage 68 is disposed through the shear plug 62, and the tube-wire 24 passes through the passage 68,

[0019] in operation, the coiled tubing18 and the BHA 16 are used to remove obstructions from: the welibore 10. In the event that the BHA 16 becomes stuck in the weilbore 10 and conventional methods for freeing the BHA 16 fail, the shear pig assembly 26 can be used to sever the tube-wire 24 proximate the BHA 16. In one embodiment, illustrated in Figures 4 and 5, the shear pig assembly 26 is introduced into the coiled tubing running string 18 at the surface 14 The coiled tubing 18 is shown spooled around reel 70. During operation, the coiled tubing 18 is unspooled from the reel 70 and then injected by an injector arrangement 72 through wellhead 74 and into the wel!bore 10 be!ow. Figure 4 depicts the reei 70 having a manifold 78 with a lateral branch 78 into whic the shear pig assembly 26 can be introduced around the tube-wire 24. The tube-wire 24 Is supplied from a reel 80. After being inserted into the coiled tubing 18 at the reei 70 a fluid pump (not shown) is used to pump the shear pig assembly 26 through the coiled tubing 18 around the reel 70 and then through the coiled tubing 18 as it runs through the injector 72 and then down into the wel!bore 10, It is noted that the shear pig assembly 26 is preferably of a small size and short axiai length such that it is capable of negotiating the bends of the coiled tubing 18 when it is coiled around the reel 70 as it is pumped through the fiowbore of the coiled tubing 18. In preferred embodiments, the shear pig assembly 26 has an axiai length of only a few inches.

[0020] Alternatively, the coiled tubing 18 could be cut at surface 14 to expose the tube wire 24. A iaunchtng assembly (not shown) of a type known in the art would then be attached to the coiled tubing 18. The shear pig assembly 26 would be guided over the tube-wire 24 and pushed into the launching assembly. A pack-off (not shown) would be installed around the tube-wire 24 at the top of the launching assembly. A pump (not shown) is then hooked up to the launching assembly and then the shear pig assembly 26 can be pumped down the coiled tubing 18 in the wellbore 10.

[0021] Once the shear pig assembly 26 has been launched or pumped through the reel 70, it will be located within the fiowbore 22 of the coiled tubing 18, as illustrated in Figure 1 , proximate the surface 14, An associated fluid pump (not shown) flows fluid into the fiowbore 22 of the coiled tubing 18, as illustrated by the arrows 78 in Figure 2, Fluid pressure acts upon the proximal end 40 of the main body 28, including the enlarged diameter portion 42 and the fins 48, thereby moving the shear pig assembly 26 downwardly within the fiowbore 22 until it reaches the annular contact fitting 25, as shown in Figure 3. The annular angled surface portion 58 of the disfai end 54 of the nose 30 contacts the contact fitting 25 and seals, allowing fluid pressure to build up at the proximal end 40 of the main body 28. Further fluid pressure from the surface 14 will thereafter rupture the frangible shear pin 52. The distal end 36 of the shaft 32 will be urged axiaily downwardly with respect to the nose 30. Axial compression of the shear plug 62 between the angled faces 38, 60 will cause the shear plug 62 to be moved radially outwardly within the shear chamber 58, as illustrated in Figure 3. The first angled surface 84 slides upon the angled face 38 while the second angled surface 88 slides upon the angled face 80. As the shear plug 62 is moved radially outwardly within the shear chamber 58, the tube-wire 24 is severed by shearing between the shear plug 82 and the neighboring main body 28 and the nose 30, as illustrated in Figure 3. As can be seen by reference to Figure 3, the tube-wire 24 is severed between the shear plug 62 and the nose 30 as well as between the shear plug 62 and the main body 28. The severed tube-wire 24 can now be withdrawn from the flowbore 22 of the running string 18. It can be seen that the main body 28 and the nose 30 are axia!ly moveable with respect to each other betwee a first position, shown in Figure 2 wherein the shearing chamber 58 Is axiaily expanded, and a second position, shown in Figure 3 wherein the shearing chamber 58 is axiaily collapsed. The shear pin 52 releasab!y secures the main body 28 and nose 30 in the first position prior to actuation.

After the tube-wire 24 is sheared downho!e, it can be pulled out of the coiled tubing 18 either by using the coiled tubing reel 70 to pull it out or by cutting the tube-wire 24 on surface 14 and attaching it to a wireline winch of a type known in the art. Once the tube-wire 24 is removed, an electric wireline unit of a type known in the art can be rigged up and a chemical or plasma cutter, of types known in the art, loaded into a lubricator and pumped downhole, as is known in the art. [0022] Those of skill in the art should understand that the exemplary shear pig assembly 26 described herein cou!d be used in other situations wherein it is desired to sever a iinear conductor other than tube-wire within a surrounding tubular other than a coiled tubing running string. Such alternative linear conductors might include siickline, light cable or smal! tubing,

[0023] The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilied in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.