GB2132253A - Improvements in and relating to drive rods for driving a string of drilling rods - Google Patents

Abstract

A drive rod for driving a string of drilling rods 12 comprises a body (44) which has an inner longitudinally extending passage of sufficient width for the string of driving rods (12) to be able to pass through the drive rod. Internally the drive rod is provided with controllable gripping means (40, 52) for gripping the string of rods. A rapid-return device is also provided for raising the drive rod relative to the drilling rod string in use. The drive rod is mounted in a rotary table (not shown). <IMAGE>

Description

SPECIFICATION Improvements in and relating to drive rods for driving a string of drilling rods The present invention relates to improvements in drive rods which, mounted in a rotary table for longitudinal displacement relative thereto, drive a string of drilling rods during the drilling of a well, such as an oii well.

At present, the drive rod is screwed to the upper end of the string of drilling rods. In each operation to add a new drilling rod, it is therefore necessary to raise the assembly consisting of the drive rod and the string of drilling rods, lock the string above the rotary table, unscrew the drive rod, screw it to a new drilling rod, lift the assembly consisting of the drive rod and the new drilling rod to bring the lower end of the new drilling rod onto the upper end of the string of drilling rods, screw the two ends together, and lower the whole of the drilling string including the new drilling rod to carry out further drilling.

These operations are time consuming and expensive; the screwing and unscrewing operations can damage the threads of the drilling rods; the stopping times can result in jamming and undesired deviations; the drive rod must have the same length as a drilling rod, and it may be positioned in the safety devices during a blow-out, thus making it impossible to close the safety devices securely.

According to one aspect of the invention there is provided a hollow drive rod for driving a string of drilling rods, and adapted to be mounted in a rotary table for driving the string of rods via an upper end portion thereof, comprising a body defining an inner longitudinal passage of sufficient width for a string of drilling rods to pass therethrough, and controllable gripping means provided within said body for gripping a string of rods.

By use of the above drive rod, it is possible, by a succession of operations of lowering and raising the drive rod, to carry out drilling to a depth equal to several times the length of the drive rod, before adding a new element to the string of drilling rods, and this addition can be made directly without previous unscrewing and without subsequent screwing up of the drive rod.

The gripping means are preferably distributed over substantially the entire length of the drive rod body.

The drive rod may be used in a drilling installation comprising from top to bottom a rotary table, a fountain tube and safety devices, the drive rod having a length substantially equal to that of the fountain tube. In this way, the drive rod can have a maximum length without interfering with the safety devices.

The inner passage of the drive rod body advantageously has a circular cross-section.

The gripping means may comprise a deformable cylindrical casing fastened in a leakproof manner at its ends to the drive rod body, inlet means for a control fluid being provided for communication with a control space defined between the inner wall of the drive rod body and the casing. The hollow drive rod body may incorporate radial guide means for the deformable cylindrical casing.

The cylindrical casing preferably comprises a reinforced resiliently flexible material.

The cylindrical casing may carry on its radially inner face gripping blocks fastened through the casing to guide pins located on the other side of the casing opposite the gripping blocks. The pins may be guided in openings in the drive rod body and by spacer collars arranged in the inner passage of the drive rod body between successive rings of guide pins.

The drive rod may be provided with a limitedspeed counterweight lifting system including winch means.

The lifting system may comprise two horizontal arms which are axially fixed to the upper end of the drive rod and which are guided on vertical brackets. The horizontal arms may be formed by tubes for the admission of control fluid to the control space.

An embodiment according to the invention will now be described, by way of example only, with reference to the accompanying drawings.

In the drawings: Figure 1 is a diagrammatic elevation of a portion of a conventional drilling installation located between the rotary table and the casing head of a well; Figure 2 is a plan view of the portion of an installation shown in Figure 1; Figure 3 is a diagrammatic elevation simiiar to that of Figure 1 of a portion of a drilling installation according to the invention which includes an embodiment of a drive rod according to the present invention; Figure 4 is a plan view of the rotary table of Figure 3; Figure 5 is a perspective view of a wedge used in the installation of Figure 3; Figure 6 is a vertical section through the drive rod of Figure 3 on a larger scale and on the lines 6-6 of Figure 8 and 6-6 of Figure 9; Figure 7 is a plan view of the drive rod of Figure 6;; Figures 8 and 9 are cross-sections through the drive rod along the lines 8-8 and 9-9 of Figure 6, respectively, during the releasing and clamping of a drilling rod element extending in the drive rod; Figure 10 is an underneath plan view of the drive rod and sectional view along the line 10-10 of Figure 6; and Figure 11 is a view in half-section and elevation of a lifting system associated with the installation according to Figure 3.

Figures 1 and 2 show a conventional rotary table 1 equipped with mounting means 2 with holes 3 for receiving a component (not shown) for driving the drive rod 4 which is screwed to the end of the uppermost rod in the string of drilling rods (not shown).

Located below the table 1 is a fountain tube 5 provided with a drilling-mud discharge chute 6 and extending between the table 1 and safety devices 7 and 8, comprising blow out preventers, e.g. a ram type preventer and an annular type preventer, such as manufactured by Hydril, which are themselves mounted on the head 9 of the well casing 10 during drilling.

Figure 3 shows the same devices 7, 8 below the rotary table 1 as in Figure 1. However in Figure 3, the conventional drive rod 4 has been replaced by a hollow drive rod 11 which has a larger crosssection than the cross-section of the conventional drive rod and an inner longitudinal passage of a width greater than that of the rods of the drilling string to allow the rods of the string of drilling rods to pass through the passage in the drive rod 11.

The rod 11 is provided in its inner passage with means for gripping an upper element 12 of the string of drilling rods, element 12 being formed by a drilling rod or an assembly of drilling rods. The gripping means are not shown in Figure 3, but an exemplary embodiment of them will be described particularly with reference to Figures 6, 8 and 9.

The drive rod 11 has in cross-section a square outer profile in the embodiment shown in Figures 2 to 10, and the component 13 for driving the rod 11, mounted on the mounting means 2, therefore has a square orifice, as shown in Figure 4.

However, the rod 11 could have a hexagonal or, more generally, a polygonal outer profile, or the rod 11 could even be provided simply with longitudinal ridges or grooves. The outer profile of the rod 11 merely has to enable it to be fixed in terms of rotation, while permitting it freedom of longitudinal displacement, relative to the rotary table.

The drive rod 11 preferably has a length equal to the length of the fountain tube 5, that is to say it will usually have a length of between about 4 and 8 metres, and most often of about 6 metres.

At its upper end, the drive rod 11 carries a thrust bearing 14 with a bidirectional effect, the fixed part 1 5 of which is secured to two horizontal arms 16 and 17. Arms 1 6, 17 are movable vertically and their free end portions 18 and 19 are guided for sliding movement along two vertical brackets 20 and 21, which act as guide rails, by a guide system which is conventional per se and has not been illustrated here. The vertical displacement of the horizontal arms 1 6 and 17 is linked to the displacement of mechanical cables 22 and 23 attached in an intermediate portion to lugs 24, 25 and 26, 27 respectively of the arms 16 and 17.Each of the cables 22 and 23 is wound at one end over a return winch 28, 29, passes over a pulley 30, 31 mounted in the upper part of the respective one of the brackets 20 and 21, and carries a counterweight 32, 33 at its other end.

When the gripping means located inside the drive rod 11 secure the latter to the drilling string element 12, the string of drilling rods drives the rod 11 and horizontal arms 16 and 1 7 downwards as a result of its own weight in proportion to the penetration of the tool (not shown) into the ground, since the counterweights 32 and 33 are lighter than the drilling train as a whole. The arms 1 6 and 1 7 therefore descend whilst the counterweights 32 and 33 rise.

When the drive rod 11 has reached its low position, it is sufficient to inactivate the inner gripping means to disengage the drive rod 11 from the element 12 of the string of drilling rods.

The drive rod 11 is then raised into its upper position as a result of the action of the counterweights 32 and 33 on the horizontal arms 1 6 and 17, this action predominating. The ascent of the drive rod 11 is slowed as a result of the action of the return winches 28 and 29. Thereafter the gripping means are reactivated and drilling continues.

By repeating the cycle of lowering and raising the drive rod 11 , which has just been described, it is possible to drill to a depth equal to the length of an element 12, that is to say to the length of a drilling rod or, better still, a pluraiity of drilling rods previously connected to one another and screwed to the string of rods already in place. It is thus possible to use, for example, elements of 27 metres formed from three rods connected to one another.

During the operation of adding a new element 12 to the string of rods, the last element 1 2 is wedged by means of wedges of conventional type, such as the wedges 34 shown in Figure 5, these being inserted into the conical central orifice 35 provided in the thrust bearing 14. This wedging could alternatively be automatic wedging.

The gripping means located inside the drive rod 11 may comprise a variety of very different types: for example, they may be mechanical, and activated by for example relative rotation of the rod 11 and element 12 resuiting in the translation of a sleeve in the drive rod 11, by jacks mounted on the rotary table and acting on pins slidable in apertures provided in the drive rod 11, or by keys forming wedges between the rod 11 and element 1 2, or they can be electromagnetic or hydraulic, such as a hydraulic pump mounted at the level of the thrust bearing 14 and locking the element 12 during relative rotation of the rod 11 and element 12.

Gripping means of hydromechanical type will now be described with reference to Figures 6 and 7 to 10, and this is considered to be preferable because it makes it possible to grip the upper drilling rod element 1 2 over a substantial area, thus avoiding the risk of damaging it.

Fluid for controlling the gripping means, for example air, is advantageously introduced into the drive rod 11 via admission or discharge tubes 36 and 37 (Figure 6) with a high mechanical resistance, which replace the arms 1 6 and 17 described above and which perform the same mechanical function as the arms 1 6, 1 7 when the drive rod 11 is lowered and raised, by sliding along vertical brackets 20 and 21 and being themselves attached to the cables 22 and 23. The admission or discharge tubes 36 and 37 are connected hydraulically at their free ends 38 and 39 to pipes (not shown) which convey or discharge the control fluid.

Figure 6 shows in its left-hand part the gripping means in inactive condition and in its right-hand part the gripping means in active condition gripping an element 12.

The gripping means located in the inner passage in the drive rod 11 comprise a deformable cylindrical casing 40 which is coaxial with the axis of symmetry of the rod 11 and is held at its upper longitudinal end by an annular endpiece 41 and which is clamped at its lower longitudinal end between a first annular connection 42 mounted on the rod 11 and a second annular leak-proofing connection 43 fastened to the first connection 42, for example by screwing.

The drive rod 11 comprises an elongate body 44, the inner passage being defined by an inner cylindrical space 45 delimited by an inner cylindrical face 46. The four external corners of the body 44 are bevelled at 47, and provided with radial guide holes 48 (produced, for example, by external milling) which receive wedges 49 attached, for example- by welding, and completing the external profile of the rod 1 1 and giving it a square shape (Figure 8).

Guide pins 50 are inserted into the radial holes 48 and are radially slidable therein. Connecting screws 51 connect each guide pin 50 to the deformable cylindrical casing 40 and to a gripping block 52 located opposite the respective pin 50 on the inside of the casing 40. The surfaces of the gripping blocks 52 facing the upper drilling rod element 12, have a cross-section in the form of an arc of a circle, and are designed to contact the element 12. Assemblies, comprising the radial guide hole 48, the guide pin 50, the gripping block 52 and the connecting screws 51, are distributed over the entire length of the dirve rod 11 and spaced from one another.

The deformable cylindrical casing 40 may comprise in particular, a resiliently flexible material, such as rubber, a synthetic elastomer or another synthetic resin, for example reinforced with fibres of high mechanical resistance, which give the casing 40 properties allowing it to return to its position of rest. It is possible to incorporate in this material, during its preparation, small steel rings for surrounding the screws 51 and to ensure leak-proofing around the screws. The guide pins 50 and the gripping blocks 52 are made, for example, of steel, and the blocks 52 may be covered with a coating with a high coefficient of friction.

As can be seen in Figure 6, the fixed part 1 5 of the bearing 14 takes the form of a fixed annular block provided with radial ducts 53 and 54 into which the tubes 36 and 37 open. The fixed annular block 1 5 is provided with a ball bearing 55 in its upper part and a ball bearing 56 in its lower part, and is clamped between a rotary lower annular body 57 and a rotary upper annular body 58, both of which are fixed to the elongate body 44. The bodies 57 and 58 are connected to one another by means of assembly bolts 59, and the body 57 is connected to the elongate body 44, for example by welding. Body 57 is provided with axially directed passages 60 which connect the radial ducts 53 and 54 with an inner control space 61 defined between the elongate body 44 and the deformable cylindrical casing 40.The annular end piece 41 of the casing 40 is fastened in a leakproof manner by means of fixed gaskets 62 to the lower annular body 57, on which it is retained by means of locking screws 63, which are cone-point screws ensuring leak-proofing. Leak-proofing between the fixed annular block 1 5 and the rotary lower annular body 57 is ensured by means of lip gaskets 64 and 65.

It will be noted that in Figure 6 the assembly bolts 59 have been shown opposite passages 60, thus making production easier. These bolts 59 are then provided with an O-ring sealing gasket 66 in their lower part.

To ensure that the forces are exerted on the casing 40 more effectively, between the pins 50, spacer collars 67 are provided, the collars 67 being coaxial with the inner cylindrical surface 46 of body 44 and having an outside diameter which is slightly smaller than the diameter of the inner cylindrical surface 46.

When the portion-of element 12 gripped by rod 11 includes a joint 68 between two drilling rods, the gripping action of any blocks 52 contacting the joint 68 is not very effective, but the other gripping blocks 52 which contact the drilling rods between joints suffice to ensure that the element 12 is gripped securely by the drive rod 11.

The portion of the upper element 12 above the drive rod 11 is grasped in a lifting system, an exemplary embodiment of which is shown partially in Figure 11. Figure 11 does not show the handling hook which is actuated by a lifting appliance (also not shown) and which is connected to a handling cradle 69 of a lifting carriage 70 provided with horizontal arms 71 carrying guide rollers 72 wich bear against vertical rails 73. The lifting carriage 70 has uprights 74 and 75, a transverse beam 76 in the upper part and a guide funnel 77 in the lower part.

The beam 76 is provided with a connection 78 connected to a mud delivery pipe 79 and to a connection 80 which is used, if required, for another injection operation, such as a cementation operation. These connections are connected by valves 81 and 82 respectively to a central vertical tubular duct 83 which is connected hydraulicaliy to a tubular portion 84 directed vertically and ending in a lower threaded end portion located just above the funnel 77.

A vertical passage extends from the duct 83 to the tubular portion 84 via three successive devices 85, 86 and 87 which respectively perform the functions of a revolving joint, a support and a rotary drive.

The device 85 comprises a fixed ring 88 carried by the duct 83 and carrying an upper bearing 89 and a lower bearing 90. Upper and lower plates 91 and 92, bear respectively against the upper and lower bearings 89 and 90 and are clamped together by clamping means 93. A sealing gasket 94 is provided between the lower plate 92 and the lower end of the duct 83.

The lower plate 92 is extended downwardly by a first tube 95 to which is attached, for example by screwing, a second tube 96 of larger diameter and provided with an internal thread which receives a retaining ring 97. The first tube 95 carries an inner gasket 98 ensuring leak-proofing with the upper end of the tubular portion 84 which extends telescopically into the first tube 95.

The tubular portion 84 is fixed to a bearing disc 99 which extends into the second tube 96 and has a portion which comes to rest on the retaining ring 97 when the tubular portion 84 is in a low position, vertical displacement of the tubular portion 84 being possible over a distance defined by the distance between the extreme upper and lower positions of the bearing disc 99 in the second tube 96.

The tubular portion 84 is fixed at the level of the device 87 to a receiving gearwheel 100 which is engageable with a pinion 101 driven, for example, by a motor 102. The assembly consisting of the motor 102 and the pinion 101 is mounted on a rack 103 so that, when required, pinion 101 can be brought into engagement with the gearwheel 100.

The funnel 77 is held on the uprights 74 and 75 by means of nuts 104 with locking pins.

A retractable guide arm 105 mounted on a displacement jack 106 and provided with detachable clamping means 107 to grip the element 12 in the string of drilling rods is provided below the funnel 77.

In use a new element 12 is brought into line with and below the tubular portion 84 (as shown in Figure 11). Since the portion 84 has a male thread 108 corresponding to the female thread 109 of the end of the element 12, the tubular portion 84 may be screwed onto the element 12 by moving portion 84 down into engagement with element 12, as a result of the descent of the lifting carriage 70, and by rotating element 84 by means of the pinion 101 which is engaged with the gearwheel 100 by operation of the rack 103.

During screwing, the bearing disc 99 descends in the second tube 96. It will be understood that by adding a threaded reducing connection to the male thread 108 it is possible to adapt the lifting carriage to any type of element 12.

Subsequently, the new element 12 is screwed, still by means of the pinion 101, onto the upper end of the string of rods, the latter being maintained locked in the drive rod 11. The motor 102 and the pinion 101 are also used when the tubular portion 84 is to be unscrewed from a string of drilling rods, which is maintained locked in the drive rod 11, before carrying out the operation of adding a new element 1 2.

There is thus provided a drive rod which enables the associated handling operations to be reduced which protects the equipment and increases the safety of the personnel.

Claims (10)

1. A hollow drive rod for driving a string of drilling rods, and adapted to be mounted in a rotary table for driving the string of rods via an upper end portion thereof, comprising a body defining an inner longitudinal passage of sufficient width for a string of drilling rods to pass therethrough, and controllable gripping means provided within said body for gripping a string of rods.

2. A drive rod according to claim 1, wherein said controllable gripping means are distributed over substantially the entire length of said hollow drive rod body.

3. A drive rod according to either claim 1 or claim 2, for use in a drilling installation comprising, from top to bottom, a rotary table, a fountain tube and safety devices, wherein said drive rod has a length substantially equal to that of said fountain tube.

4. A drive rod according to any one of the preceding claims, wherein said gripping means comprise a deformable cylindrical casing connected in leak-proof manner at its ends to said drive rod body, inlet means being provided for a control fluid and communicating with a control space located between the inner wall of said drive rod body and said casing, said drive rod body incorporating radial guide means for said deformable cylindrical casing.

5. A drive rod according to claim 4, wherein said casing carries on its radially inner face gripping blocks fastened through said casing to guide pins located on the other side of said casing opposite said gripping blocks.

6. A drive rod assembly comprising a drive rod according to any one of claims 1 to 5 and a limited-speed counterweight lifting system including winch means.

7. A drive rod assembly according to claim 6, wherein said lifting system includes two horizontal arms which are fixed, except in terms of rotation, to the upper end of said drive rod and which are guided on vertical brackets.

8. A hollow drive rod for driving a drilling string substantially as herein described with reference to Figures 3 to 10 of the accompanying drawings.

9. A drive rod assembly for driving a drilling string substantially as herein described with reference to Figures 3 to 11 of the accompanying drawings.

10. A drilling installation including a hollow drive rod for driving the drilling string substantially as herein described with reference to Figures 3 to 11 of the accompanying drawings.