Intra-perforating gun swivel

Abstract: A perforating gun, adapted to be disposed in a deviated borehole, includes an ultra-gun swivel (10c) located between a first plurality of charges (10a2) and a second plurality of charges (10b2) of the perforating gun. The swivel includes a first housing, a second housing, and thrust and radial bearings disposed between the surfaces of the first and second housing for allowing the first housing to rotate with respect to the second housing and therefore the first plurality of charges to rotate with respect to the second plurality of charges of the perforating gun.

Description: BACKGROUND OF THE INVENTION The subject matter of the present invention relates to a swivel disposed in a perforating gun for enabling opposite parts of the perforating gun to independently swivel about an axis. Perforating guns are sometimes disposed in deviated boreholes. When disposed in the deviated borehole, the perforating gun is rotated in order to direct the charges in a selected direction into the formation. Normally, a swivel located in the tubing string above the firing head of the perforating gun enables the perforating gun to rotate: such a perforating gun is described in US-A-4 523 649, which represents the prior art as referred to in the pre-characterising portion of claim 1. However, since the swivel is located in the tubing string above the firing head of the gun, certain problems are created: (1) alignment error builds up in orientated guns, (2) torque builds up along the gun string, and (3) the swivel interferes with certain components above the gun string, such as hydraulic flow tubes, drop bars and slickline tools. SUMMARY OF THE INVENTION According to the present invention, there is provided a perforating gun comprising: A perforating gun, comprising: a first charge; a second charge axially spaced from the first charge; and swivel means ; characterised in that the swivel means is disposed between the first charge and the second charge for enabling the first charge to rotate about a longitudinal axis relative to said second charge. In a preferred embodiment, the swivel means includes radial and annular thrust bearings interconnecting a first end of the swivel means to a second end of the swivel means. The first part of the perforating gun includes a plurality of charges interconnected by a detonating cord, a trigger shape charge being disposed at the end of the detonating cord for initiating detonation of a further detonating cord when the trigger charge detonates. The further detonating cord is disposed in the second part of the perforating gun and is connected to a further plurality of charges. Since the intra-gun swivel means is located within the perforating gun string, and not above the perforating gun within the tubing string, alignment error built up in oriented guns can self correct. In addition, torque cannot build up along the perforating gun string; and the swivel means does not interfere with any components above the perforating gun string, such as hydraulic flow tubes, drop bars, and slickline tools. Further scope of applicability of the present invention will become apparent from the detailed description presented hereinafter. It should be understood, however, that the detailed description and the specific examples, while representing a preferred embodiment of the present invention, are given by way of illustration only, since various changes and modifications within the scope of the invention as defined by the appended claims will become obvious to one skilled in the art from a reading of the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS A full understanding of the present invention will be obtained from the detailed description of the preferred embodiment presented hereinbelow, and the accompanying drawings, which are given by way of illustration only and are not intended to be limitative of the present invention, and wherein: figure 1 illustrates the intra-gun swivel located within a perforating gun and separating the perforating gun into a first part and a second part; and figure 2 illustrates a more detailed construction of the intra-gun swivel of figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to figure 1, a perforating gun 10 includes a first part 10a and a second part 10b. A swivel 10c interconnects the first part 10a of the perforating gun to the second part 10b of the perforating gun. The swivel 10c includes, in the embodiment of invention shown in figure 1, an inwardly directed flange 10c1 connected to the second part 10b of the perforating gun, an outwardly directed flange 10c2 connected to the first part 10a of the perforating gun, and a thrust bearing 10c3 disposed between the inwardly directed flange 10c1 and the outwardly directed flange 10c2. A detonating cord 10a1 interconnects a plurality of charges 10a2 disposed within the first part 10a of the perforating gun. A further charge 10a1A is connected to the end of the detonating cord 10a1 below the swivel 10c for initiating detonation of a further detonating cord 10b1 disposed within the second part 10b of the perforating gun 10. The further detonating cord 10b1 interconnects a further plurality of charges 10b2 disposed within the second part 10b of the perforating gun. A booster 10b1A is disposed at the end of the further detonating cord 10b1 adjacent the further charge 10a1A for receiving a jet from the further charge 10a1A when the further charge 10a1A detonates and transferring a detonation wave to the further detonating cord 10b1. Referring to figure 2, a more detailed construction of the intragun swivel 10c of figure 1 is illustrated. Figure 2 illustrates a more detailed construction of the swivel 10c, interconnected between the first part 10a and the second part 10b of the perforating gun 10, the swivel 10c in figure 2 comprising a first housing 10c4 including two inwardly directed flanges 10c1 and a second housing 10c5 connected to the first housing 10c4 and including an outwardly directed flange 10c2 which is disposed within a recess defined by the two inwardly directed flanges 10c1 of the first housing 10c4. A thrust bearing 10c3B is disposed on the upper and lower surfaces of the outwardly directed flange 10c2 and a radial bearing 10c3A is disposed between an outer wall surface of the second housing 10c5 and an inner wall surface of the first housing 10c4. A detonating cord 10a1 is connected to a further (trigger) charge 10a1A within the first housing 10c4 and a further detonating cord 10b1 is connected to a booster 10b1A within the second housing 10c5. The detonating cord 10a1 is connected to a first plurality of charges in the first part 10a of perforating gun 10 and the further detonating cord 10b1 is connected to a second plurality of charges in the second part 10b of the perforating gun 10. Due to the existence of the thrust bearing 10c3B and the radial bearing 10c3A between the first and second housings of the swivel, the first housing 10c4 may independently rotate with respect to the second housing 10c5. A functional operation of the intragun swivel of the present invention will be set forth in the following paragraphs with reference to figures 1 and 2 of the drawings. In figure 1, as a result of the thrust bearing 10c3 disposed between the outwardly directed flange 10c2 of the first part 10a and the inwardly directed flange 10c1 of the second part 10b, the first part 10a of the perforating gun 10 is adapted to rotate with respect to the second part 10b of the perforating gun 10. When the first part 10a of perforating gun 10 is twisted or rotated with respect to the second part 10b, the bearing 10c3 rotates thereby allowing the inwardly directed flange 10c1 to move with respect to the outwardly directed flange 10c2. Since the plurality of charges 10a2 are disposed within the first part 10a of perforating gun 10, and the further plurality of charges 10b2 are disposed within the second part 10b of perforating gun 10, rotation of the first part 10a with respect to second part 10b enables the charges 10a2 in the first part to also rotate relative to the further charges 10b2 in the second part 10b. When it is desired to detonate the charges 10a2/10b2 in the perforating gun 10, a detonation wave is propagated along detonating cord 10a1 thereby detonating the plurality of charges 10a2 in the first part 10a of perforating gun 10. The further charge 10a1A detonates when the detonation wave is received therein. Detonation of the further charge 10a1A causes a further detonation wave to propagate from booster 10b1A along further detonating cord 10b1 to the further plurality of charges 10b2, initiating detonation of the further plurality of charges 10b2. Since the swivel 10c id disposed between the first part 10a and the second part 10b of the perforating gun 10, alignment error does not build up in the gun 10, torque does not build up within the perforating gun 10 string, and no interference is created with respect to the components in the tubing above the gun string. In figure 2, when first housing 10c4 is rotated with respect to second housing 10c5, the thrust bearings 10c3B allow the outwardly directed flange 10c2 on the second housing 10c5 to move in its recess with respect to the two inwardly directed flanges 10c1 on the first housing 10c4. In addition, the radial bearing 10c3A allows the outer wall surface of the second housing 10c5 to move with respect to the inner wall surface of the first housing 10c4. In figure 2, when the detonation wave is received by the further (trigger) charge 10a1A from the detonating cord 10a1, the further charge 10a1A detonates thereby initiating the propagation of a further detonation wave in the further detonating cord 10b1 from booster 10b1A. The invention being thus described, it will be obvious that the same may be varied in many ways. All such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims: A perforating gun, comprising: a first charge (10a2); a second charge (10b2) axially spaced from the first charge (10a2); and swivel means (10c); characterised in that the swivel means (10c) is disposed between the first charge (10a2) and the second charge (10b2) for enabling the first charge (10a2) to rotate about a longitudinal axis relative to said second charge (10b2). The perforating gun of claim 1, further comprising: a first housing (10a) enclosing the first charge (10a2); and a second housing (10b) enclosing the second charge (10b2). The perforating gun of claim 2, wherein said first housing (10a) and said second housing (10b) each include an end disposed adjacent one another; and wherein said swivel means (10c) comprises bearing means (10c3) disposed between interfacing surfaces of the adjacent ends of said first housing (10a) and said second housing (10b), the bearing means (10c3) enabling said first housing (10a) including the first charge (10a2) to rotate with respect to said second housing (10b) including said second charge (10b2). The perforating gun of claim 3, wherein said first housing (10a) includes an outwardly directed flange (10c2), said second housing (10b) including an inwardly directed flange (10c1), said bearing means (10c3) being disposed between the inwardly directed flange (10c1) and the outwardly directed flange (10c2), the bearing means (10c3) allowing the inwardly directed flange (10c) of said second housing (10b) to rotate with respect to the outwardly directed flange (10c2) of said first housing (10a). The perforating gun of claim 4, further comprising: a first detonating cord (10a1) disposed within said first housing (10a) and connected to said first charge (10a2); further trigger charge means (10a1A) disposed at an end of said first detonating cord (10a1) for detonating in response to a detonation wave propagating along said first detonating cord; a second detonating cord (10b1) disposed within said second housing (10b) and connected to said second charge (10b2); and booster means (10b1A) disposed at an end of said second detonating cord (10b1) and being further disposed adjacent said further trigger charge (10a1A) in said perforating gun (10) for transmitting a detonation wave into said second detonating cord (10b1) in response to detonation of said trigger charge (10a1A). A method of rotating a perforating gun (10) when said gun is disposed in a borehole, said perforating gun including a swivel (10c) disposed between a first end (10a) and a second end (10b) of said gun, said first end including a first charge (10a2), said second end including a second charge (10b2), comprising: twisting said first end (10a) of said perforating gun; and rotating said first end (10a) of said gun with respect to said second end (10b) of said gun, said swivel (10c) allowing said first end to rotate with respect to said second end. The method of claim 6, wherein said swivel (10c) includes at least one bearing (10c3) disposed between adjacent interfacing surfaces of said first end (10a) and said second end (10b) of said perforating gun (10), comprising the step of: rotating said first end (10a) of said gun with respect to said second end (10b), the bearing (10c3) of said swivel (10c) allowing the adjacent interfacing surfaces of said first end (10a) and said second end (10b) of said perforating gun to move with respect to one another.

Inventors: HUBER KLAUS, MISZEWSKI ANTONI, HUBER, KLAUS, MISZEWSKI, ANTONI
Applicants: SCHLUMBERGER HOLDINGS, SCHLUMBERGER LTD, SCHLUMBERGER SERVICES PETROL, SCHLUMBERGER TECHNOLOGY BV, SCHLUMBERGER HOLDINGS LIMITED, SCHLUMBERGER LIMITED, SCHLUMBERGER TECHNOLOGY B.V., SERVICES PETROLIERS SCHLUMBERGER, (FORMERLY SOCIETE DE PROSPECTION ELECTRIQUE SCHLUMBERGER)
Application year: 1991
Main classification: E21B43
IPC codes: E21B43, E21B23