WEIGHT COMPENSATION DEVICE

Abstract: An apparatus for facilitating the connection or disconnection of a tubular to or from a string of tubulars, which apparatus comprises a weight compensating device (12, 13, 12', 13') which can be suspended from a travelling block (TB) or a top drive (TD) or a swivel, characterised in that said apparatus further comprises a member (11) which can support a primary elevator (31) and which can, in use, be raised and lowered by said weight compensating device (12, 13, 12', 13') to enable a tubular (JC) to be raised and lowered with respect to a string of tubulars (ST) and which can move to a load bearing position in which it can raise and lower said string of tubulars.

Description: WEIGHT COMPENSATION DEVICE This invention relates to an apparatus and a method for facilitating connection or disconnection of a tubular to or from a string of tubulars, and is particularly, but not exclusively for facilitating the connection or disconnection of casing to or from a string of casing using a top drive or a travelling block of a derrick of an oil or gas well . During the drilling of oil and gas wells it is necessary to connect and disconnect tubulars for use therein. Recently, there has been the need to use casing of a very large diameter for lining the well . In particular, modern casing may be forty-eight inches in diameter . The weight of a single joint of modern casing causes many problems. In particular, casing is usually threaded. When a joint of casing is connected and disconnected from the string of casing, there is a high probability that the threads will become damaged by collisions therebetween . It has been proposed to use a device called a "single joint compensating elevator" as disclosed in EP- A-0 171 144. The device enables the weight of a single joint to be compensated for, such that when the joint is lowered or raised to or from a string, the effective weight of the joint is zero. A pneumatic bellows or the like allows small adjustments to be made to allow the joint of casing to be made up to the string of casing. The device also allows over compensation to be made , such that upon disconnection of a joint from the string of casing, the joint springs from the string of casing. The device depends from the primary elevator of the rig, with a single joint elevator depending therefrom. The above described arrangement requires the device to be attached to the elevator prior to each connection or disconnection and removed therefrom prior to lowering or raising the string, which is carried out by the primary elevator . This procedure wastes valuable rig time. The present invention provides an apparatus for facilitating the connection or disconnection of a tubular to or from a string of tubulars , which apparatus comprises a weight compensating device which can be suspended from a travelling block or a top drive or a swivel , characterised in that said apparatus further comprises a member which can support a primary elevator and which can, in use, be raised and lowered by said weight compensating device to enable a tubular to be raised and lowered with respect to a string of tubulars and which can move to a load bearing position in which it can raise and lower said string of tubulars . Preferably, said member comprises a stem arranged substantially in parallel with said weight compensating device . Advantageously, said stem is rigid. Preferably, said stem comprises an end stop which rests on the top of said apparatus when said member is in its load bearing position. Advantageously, said stem comprises a yoke for attachment of the primary elevator . Preferably, said weight compensating device comprises at least one piston and cylinder. Advantageously, said at least one piston and cylinder is pneumatically operated. Preferably, said primary elevator is rota able with respect to said weight compensating device . Advantageously, said apparatus further comprises a motor for rotating said primary elevator . Preferably, said apparatus further comprises a brake for inhibiting rotation of said primary elevator. Advantageously, said weight compensating device is shear pinned to said primary elevator. Preferably, said apparatus is provided with said primary elevator. The present invention also provides a method for facilitating the connection of a tubular to a string of tubulars using an apparatus in accordance with the present invention, said method comprising the steps of positioning a tubular in the primary elevator of said apparatus, lowering said primary elevator to bring said tubular into contact with a string of tubulars held in a spider therebelow, and connecting said tubular to said string of tubulars, and lowering said string of tubulars on said primary elevator. The present invention further provides a method for facilitating the disconnection of a tubular from a string of tubulars using an apparatus in accordance with the present invention, said method comprising the steps of positioning the primary elevator on a string of tubulars, lifting said string of tubulars from a well bore, securing said string of tubulars in a spider, disconnecting a tubular, the weight compensating device of said apparatus compensating or overcompensating for the weight of said tubular, and raising the tubular clear of said string of tubulars There is also provided an elevator provided with a bearing to facilitate rotation between said elevator and an item held in said elevator. For a better understanding of the invention, reference will now be made, by way of example, to the accompanying drawings , in which : Figure 1 is a typical prior art arrangement for facilitating the connection of a tubular to a string of tubulars, the arrangement incorporating a single joint compensating elevator; Figure 2A is a front view of an apparatus in accordance with the invention, in use; Figure 2B is an enlarged side view of part of the apparatus of Figure 2A; Figure 3 is a cross sectional view of the apparatus of Figure 2A; Figure 4A is a schematic representation of a compensating device, in use; Figure 4B is an enlarged schematic representation of part of the apparatus of Figure 4A; Figures 4C-F are schematic representations of alternative compensating devices which may be used in the apparatus of Figure 2A; Figures 5A-C are schematic representations of a control unit incorporating the control panel of Figure 4A; Figures 6A-G are schematic representations of various stages involved in a method according to the present invention using the apparatus as shown in Figure 2A; Figure 7A is a front view of a primary elevator; Figure 7B is a top plan view of the primary elevator of Figure 7A; and Figure 7C is a cross-section of the elevator of Figure 7A. Referring to Figure 1 there is shown a prior art arrangement for facilitating the connection of a tubular to a string of tubulars, the arrangement including a single joint compensator J. The single joint compensator J depends from a primary elevator (not shown) which is attached by bails (not shown) to a top drive (not shown) or a travelling block (not shown) of a derrick (not shown) . A single joint elevator E depends from the single joint compensator J via a swivel T and cables C. The single joint elevator E is shown supporting a joint of casing P that is to be connected the top of a string of casing N held in the slips (not shown) in the floor of the rig. A tong O is located below the single joint elevator E and is positioned about the joint of casing P. The tong O is used to rotate the joint of casing to facilitate connection with the string of casing N. The single joint compensator J is controlled from a control console S which receives compressed air from a rig air supply A. The control console S is located on the floor of the rig nearby. An air hose H extends from the control console S to the single joint compensator J. Referring now to Figures 2A, 2B and Figure 3, there is shown an apparatus in accordance with the invention generally identified by reference numeral 1 retaining a joint of casing JC. The apparatus 1 comprises a supporting bracket 2 having two lifting lugs 3 fixed thereto for attachment to bails (not shown) of a top drive or travelling block. The supporting bracket 2 is provided with a plate 4 which is attached thereto by bolts 5 with a spacer 6 arranged therebetween. A central hole 7 runs through the plate 4, the spacer 6 and the supporting bracket 2. A lower plate 8 is welded to the bottom of the supporting bracket 2. Bushings 9 and 10 are provided in the supporting bracket 2 to facilitate rotation of a stem 11 provided in the central hole 7. Four piston and cylinders 12, 13, 12' and 13' , are spaced about the plate 4 and attached thereto by lugs 14 and 15 via pins 16 and 17. The lower ends of the piston and cylinders 12, 13, 12' and 13' are attached to a lower support 18 via lugs 19, 20, 19' and 20' and shear pins 21, 22, 21' and 22' . The shear pins 21, 22, 21' and 22' are provided such that in the event of overloading the piston and cylinders 12, 13, 12' and 13', the shear pins 21, 22, 21' and 22' will shear releasing the piston and cylinders 12, 13, 12' and 13' from connection between the supporting bracket 2 and the lower support 18. The lower support 18 comprises a plate 23 which is provided with a central hole 24 therethrough for stem 11 to pass through. A rotatable plate 25 is fast with the stem 11 and is seated on bearings 26. The bearings 26 are supported by the lower support 18. The stem 11 is provided with an upper stop 27. Upon full extension of said piston and cylinders 12, 13, 12' and 13' , the upper stop 27 engages the plate 4 and transfers any weight from the piston and cylinder 8 and 9 thereto. The weight held by the stem 11 is transferred through the plate 4 , the spacer 6 to the supporting bracket 2 and to the bails (not shown) . The lower end of the stem 11 extends below the lower support 18 and is provided with a yoke 28 for retaining the arms 29 and 30 of a primary elevator 31. A motor 32 is mounted to the underside of plate 18 to rotate the stem 11. A shield 33 protects the motor 32. A brake 34 is provided for engaging the stem 11 to inhibit rotation thereof. The stroke length of the piston and cylinders is preferably twice the length of the thread of the casing being connected. About 36cm (14 inches) is appropriate for threads of 13cm to 18cm (5 to 7 inches) in length which allows 18cm (7 inches) of upward and 18cm (7 inches) of downward movement. The stroke is commensurate with the length of the piston which may be chosen as desired. Figure 2B shows a scale 35 marked on to the piston of the piston and cylinder 13 to give an indication to the operator of the stroke position. The scale could be in the form of markers, indicia, numerals, or stripes. As an alternative to physical marks , an electronic sensor or other position indicator could be used. Another alternative would be to measure the quantities of fluid in the cylinder to determine stroke position . Referring to Figures 6A to 6H, there is shown the apparatus 1 in use . The apparatus 1 is hung from a travelling block TB (or a top drive) by bails B. The bails B are connected to the lugs 3 of the supporting bracket 2. For connection of a joint JC of casing to a string ST of casing, the joint JC is placed in the primary elevator 31 (Fig. 6A-B) . The piston and cylinders 12, 13, 12' and 13' are now set to compensate for the weight of the joint JC by use of a control console CC . Once set, the same setting may be used for subsequent joints of the same weight. The travelling block TB (or top drive) is then lowered so that the pin on the lower end of the joint JC enters the box of the upper end of the string ST of casing (Fig. 6C-D) . Since the weight of the joint JC is compensated for, the threads of the pin and box are unlikely to be damaged if they collide. A stabbing guide may be used during this procedure to guide the pin into the box. A motor 32 may now be used to rotate the joint JC in order to threadly mate the joint JC with the string ST. A power tong O is then used to torque the connection up to the required torque. Make-up can hence be conducted with the weight of the joint J being compensated for (Fig. 6F) . The piston and cylinders 12, 13, 12' and 13' are now extended and the apparatus 1 raised until stop 27 of the stem 11 abuts the plate 4 of the supporting bracket 2 (Fig 6G-H) and slightly raises the string ST . The spider SP in the floor of the rig is then released. The entire string ST is held by the apparatus 1. The weight of the string ST is taken through the yoke 28, the stem 11 and the supporting bracket 2. The string ST is then lowered by the travelling block TB (or top drive) into the well bore WL. The travelling block TB is lowered by operation of a draw works DW via cable CS running over a crown block CB located at the top of a rig RG. The spider SP is then reapplied to the string ST . Primary elevator 31 is then removed from the string ST. The apparatus 1 is raised by the travelling block TB (or top drive) in readiness for a subsequent joint. For disconnection of a joint JC from a string ST, the primary elevator 31 is placed around the top of the string ST. The piston and cylinders 12, 13, 12' and 13' are extended until the stop 27 of the stem 11 abuts the plate 4 of the supporting bracket 2. The apparatus 1 is now raised until the primary elevator 31 abuts the box of the top joint JC of the string ST. The spider SP in the floor of the rig is released. The entire weight of the string ST is taken by the apparatus 1. The weight of the string ST is taken through the yoke 28, the stem 11 and the supporting bracket 2. The travelling block TB (or top drive) is raised, lifting the string ST until a joint JC is (or two or three joints are) above the spider SP (Fig 6G-H) . The spider SP is reapplied to the string ST. The elevator 31 is lowered until the spider SP takes the full weight of the string ST. The piston and cylinders 12, 13, 12' and 13' are now set to compensate for slightly greater than the expected weight of the joint JC, (or the weight of two or three joints as required) . A power tong O is used to break the connection between the joint JC and the string ST. The power tong O is then removed. The stem 11 may now be rotated by the motor 32 until the joint JC is free from the string ST. The piston and cylinders 12, 13, 12' and 13' are over compensating for the weight of the joint JC and hence the joint JC is lifted from the string ST. Damping is provided by the piston and cylinders 12, 13, 12' and 13' so that the joint JC does not "bounce" back on to the top of the string ST. The joint JC is removed from the primary elevator 31 and placed in a rack using pipe handling equipment (not shown) . The apparatus 1 is now ready for the disconnection of subsequent joints from the string ST. Referring now to Figures 4A and 4B there is shown schematically, an apparatus 100. The apparatus 100 is attached to a top drive D by a shackle 101 and bails 102. A safety chain CH is provided between the shackle 101 and the apparatus 100. A shear pin 103 or other device links the apparatus 100 to the shackle 101. In the event that the shear pin 103 shears, the safety chain CH will prevent the apparatus 100 from falling on to the floor of the rig. The shear pin 103 may be designed to shear at 2.7 tonnes (3 tons) . This arrangement protects the apparatus 100 from being subjected to the entire weight of the string if the piston and cylinders fail to extend to allow transfer of weight through the stem. The chain should be designed to fail at three times the expected load. A control console CC is provided for controlling the apparatus 101. The apparatus 100 is linked to the control console by control line H. Figures 4C to 4F show four arrangements of piston and cylinders . Figure 4C shows two piston and cylinders 104 and 105 in parallel with each other. Figure 4D shows on piston and cylinder 106. Figure 4E shows three piston and cylinders 107, 108 and 109 in parallel with each other. Figure 4F shows four piston and cylinders 110, 111, 112 and 113 in parallel with each other. The piston and cylinders have a bore of 182cm 2 (28.27 square inches); a rod area of 9.58cm 2 (1.485 square inches) ; an effective area (bore minus rod) of 172cm 2 (26.8 square inches) and is able to support about 1.1 tonnes (2500 pounds). The pressure of the pneumatic fluid inside the cylinder is about 6.4 Bar (93.3psi) . The pressure required to support two tons is about 5.5 Bar (80psi) . The embodiment of Fig . 4C can support 5 tons at 6.4 Bar (93.3psi) and 4 tons at 5.5 Bar (80psi) . The embodiment of Fig . 4E can support 7.5 tons at 6.4 Bar (93.3psi) and 6 tons at 5.5 Bar (80psi) . The embodiment of Fig. 4F can support 10 tons at 6.2 Bar (90psi) and 8 tons at 5.5 Bar (80psi) . If a multi piston and cylinder apparatus is used, and light tubulars are to be handled, only one or more piston and cylinders need be used. The other piston and cylinders can vent through vent V. Figure 4G shows schematically a circuit diagram of a linked piston and cylinder arrangement generally identified by reference numeral 200. Flow lines 201 and 202 link the two lower interiors of the cylinder 203, 204 and 205, 206 of the cylinders 110, 111, 112 and 113. A flow line 207 links the two flow lines 201 and 202. The flow line 207 leads to a control console CS . Pistons 208, 209, 210 and 211 are connected to piston rods 212, 213, 214 and 215 a portion of which extends below a plate 216 on to which the cylinders are mounted. An upper plate may be arranged on top of the cylinders for stability. A manifold may be used for providing each cylinder with equal quantities of fluid for even actuation thereof. Each cylinder may be provided with an isolation valve for selectively venting each cylinder . Figures 5A-5C show an embodiment of a control console CS for use with the system of Figure 4A. The control console SC includes a fluid hose reel 301 on a base 302, a make-up pressure indicator 303, a break-out pressure indicator 304 , a make-up regulator pressure control know 305, a make-up relief valve control knob 306, and a break-out regulator pressure control knob 307. Figures 7A-7C show an elevator 400 according to the present invention with a body 401 with parts 402 and 403 hinged together by hinge 404 for selective emplacement around and removal from a tubular, releasable locking apparatus 405, a bore 406 through the body, lifting ears 407 on the body, a shoulder 408 around the top of the bore 406, and a roller bearing apparatus 409 with halves 410 and 411 on the shoulder 408 each with a plurality of roller bearings 412. A collar or other appropriate part of a tubular (not shown) may rest and move on the roller bearings 412 and thus rotation of the collar (and of, therefore, the tubular and other tubulars connected to and beneath it) is facilitated. The primary elevator 31 may have such roller bearing apparatus or, alternatively, any suitable known roller and/or bearing devices or mechanisms may be used on the shoulder 408 or on a top portion of the elevator 400. Such bearing and/or roller apparatus may also be provided for multiple (dual, quad, etc.) string elevators. In the embodiment of Figure 2A, there are four piston and cylinders used, which may be hydraulic or pneumatic, in this embodiment, however any number could be used including one, two, three, four, five or six. A bellows air spring may be used instead of the piston and cylinders . If required, the motor 32 can be used to rotate the entire string for purposes such as facilitating insertion of tubulars into the well bore. It should be noted that the above apparatus could be used for connecting and disconnecting any sort of tubular including casing, liner, thin walled pipe, drill pipe or any tool for connection or disconnection to of from a string of tubulars . It is envisaged that the stem could be an enlarged piston rod of a piston and cylinder of the weight compensating device . An end stop may be provided on the end of the piston rod to transfer the weight of a string of tubulars to a support when the piston is in a fully extended position. It is also envisaged that the stem could be a chain.

Claims: Claims : 1. An apparatus for facilitating the connection or disconnection of a tubular to or from a string of tubulars, which apparatus comprises a weight compensating device (12 , 13 , 12' , 13' ) which can be suspended from a travelling block (TB) or a top drive (TD) or a swivel, characterised in that said apparatus further comprises a member (11) which can support a primary elevator (31) and which can, in use, be raised and lowered by said weight compensating device (12 ,13, 12' , 13' ) to enable a tubular (JC) to be raised and lowered with respect to a string of tubulars (ST) and which can move to a load bearing position in which it can raise and lower said string of tubulars . 2. An apparatus as claimed in Claim 1 , wherein said member (11) comprises a stem (11) arranged substantially in parallel with said weight compensating device (12,13,12' ,13') . 3. An apparatus as claimed in Claim 2 , wherein said stem (11) is rigid. 4. An apparatus as claimed in Claim 3 , wherein said stem (11) comprises an end stop (27) which rests on the top of said apparatus when said member is in its load bearing position. 5. An apparatus as claimed in Claim 2 , 3 or 4 , wherein said stem (11) comprises a yoke (28) for attachment of the primary elevator (31) . 6. An apparatus as claimed in any preceding claim, wherein said weight compensating device (12 ,13,12' , 13' ) comprises at least one piston and cylinder. 7. An apparatus as claimed in Claim 6 , wherein said at least one piston and cylinder (12,13,12' ,13' ) is pneumatically operated. 8. An apparatus as claimed in any preceding claim wherein said primary elevator (31) is rotatable with respect to said weight compensating device (12,13,12' ,13') . 9. An apparatus as claimed in 8, further comprising a motor (32) for rotating said primary elevator (31) . 10. An apparatus as claimed in Claim 8 or 9, further comprising a brake (34) for inhibiting rotation of said primary elevator (31) . 11. An apparatus as claimed in any preceding claim, wherein said weight compensating device (12 , 13 , 12' , 13' ) is shear pinned to said primary elevator (31) . 12. An apparatus as claimed in any preceding claim provided with said primary elevator (31) . 13. A method for facilitating the connection of a tubular to a string of tubulars using an apparatus as claimed in Claim 12 , said method comprising the steps of positioning a tubular in the primary elevator of said apparatus, lowering said primary elevator to bring said tubular into contact with a string of tubulars held in a spider therebelow, and connecting said tubular to said string of tubulars, and lowering said string of tubulars on said primary elevator . 14. A method for facilitating the disconnection of a tubular from a string of tubulars using an apparatus as claimed in Claim 12 , said method comprising the steps of positioning the primary elevator on a string of tubulars, lifting said string of tubulars from a well bore, securing said string of tubulars in a spider, disconnecting a tubular, the weight compensating device of said apparatus compensating or overcompensating for the weight of said tubular, and raising the tubular clear of said string of tubulars 15. An elevator provided with a bearing (409) to facilitate rotation between said elevator (400) and an item held in said elevator (400) .

Inventors: ALBRIGHT STEVEN LEE, BEARB JEAN DONALD, BIRDWELL JOHN CLEVELAND, HAYES MICHAEL WARREN, LEICHT FREDERICK MARION, SPREIJ LEENDERT, ALBRIGHT, STEVEN, LEE, BEARB, JEAN, DONALD, BIRDWELL, JOHN, CLEVELAND, HAYES, MICHAEL, WARREN, LEICHT, FREDERICK, MARION, SPREIJ, LEENDERT
Applicants: LUCAS BRIAN RONALD, WEATHERFORD LAMB, LUCAS, BRIAN, RONALD, WEATHERFORD/LAMB, INC.
Application year: 1998
Main classification: E21B19
IPC codes: E21B19