The present invention relates to a top drive well drilling installation and methods for performing well operations.
Pending application WO2014/178709 of the same applicant discloses a top drive well drilling installation comprising a drilling tower that is provided with vertical rails supported by the drilling tower. A trolley is guided along the vertical rails. The trolley is suspended from a travelling block of a hoisting device, commonly referred to as drawworks in the drilling industry. The hoisting device comprises a cable and a winch, as well as a crown block. The travelling block is suspended from the crown block by the cable. Operation of the winch allows to move the travelling block and the trolley up and down along the rails.
The mentioned known installation further comprises a top drive unit and a rotatable tubular stem that is to be connected to the upper end of a drill string for rotation therewith about an axis of the drill string. The top drive unit further includes a motor adapted to rotate the tubular stem and thereby the connected drill string. The top drive unit is supported by the trolley, at least so as to absorb reaction torque from the motor of the top drive unit.
In order to suspend the drill string, e.g. when it is detached from the top drive unit, the mentioned known installation comprises an elevator that is adapted to suspend the drill string there form, e.g. during tripping.
Commonly, the elevator is held by an elevator support assembly embodied as two pivotable arms, which at their upper end are pivotally connected to a suspension body that is in turn suspended on a shoulder formed on the rotatable tubular stem of the top drive unit. These arms or links as they are often called, are very robust as they are designed to absorb the load of the entire drill string during activities such as tripping. An actuator is provided that is operable to move the elevator between an operative position on the drill string axis and a retracted position away from the drill string axis.
Alternatively, as disclosed in WO2014/178709, the elevator support assembly is embodied as a direct drill string load bearing connection between the elevator and the trolley, independent from the top drive unit.
These known arrangements are not entirely satisfactory. It is therefore an object of the present invention to propose an improved installation or at least an alternative installation.
The present invention provides an installation according to the preamble of claim 1, which is based on WO2014/178709, which is characterized in that the top drive well drilling installation further comprises:
The inventive design allows, in embodiments, to achieve relevant advantages over the prior art designs.
For example the top drive unit now does not need to be designed to support the entire drill string, as even during drilling, when the pipe and the tubular stem are attached, the load of the suspended drill string is supported by the rotating headclamp, making its design less complex and costly.
The rotating headclamp is provided with multiple mobile pipe retainers supported by the rotary body. Hence, the retainers, and the pipe they retain, are rotatable with the rotary body with respect to the support frame. The mobile pipe retainers are mobile so as to provide an operative and a non-operative position of the rotating headclamp. In the non-operative position the pipe retainers are adapted to allow passage of a pipe of the drill string through the pipe passage of the open-centered body, in particular in an upward direction. In the operative position the pipe retainers engage below a shoulder of a pipe of the drill string extending through the pipe passage so as to suspend said drill string therefrom. Such a type of clamp is often referred to as a collar-type clamp. It is noted that the shoulder may also be provided on a tool joint or a box member, connected to a pipe.
In embodiments, the pipe retainers engage below the shoulder of a tool, e.g. a casing tool including an internal and/or external gripper assembly for gripping casing or a casing running tool.
Advantageously, the mobile pipe retainers have a clamping jaw to engage on a pipe, which is preferably an exchangeable clamping jaw to be able to match the diameter and/ or shape to the type of pipe. Hence, when a different type of pipe is to be handled, it is not necessary to replace the entire headclamp but only the clamping jaws.
In a particular advantageous embodiment, two sets of multiple, e.g. three, mobile pipe retainers are provided, each set being adapted to retain a different type of pipe, e.g. each comprising a different type of clamping jaws, and wherein it is possible to have one set in the non-operative position and the other in the operative position. Accordingly, when a different type of pipe is to be handled, it is not necessary to replace the entire headclamp or the clamping jaws, but simply the other set of pipe retainers may be brought in the operative position.
In embodiments in which the support frame allows the presence of a rotating headclamp and a spare rotating headclamp, it is thus possible to have pipe retainers for four different types of pipe readily available.
Advantageously, mobile pipe retainer is embodied as a lever comprising an arm and a fulcrum, which fulcrum is fixed to the rotary body and wherein one end of the arm is adapted to—in the operative position—engage on the pipe, and in the non-operative position has cleared the area in line with the pipe passage to allow the passage of a pipe of the drill string, and wherein the other end of the arm is operable by an actuator to move the opposite end of the arm between the operative and the non-operative position. Advantageously, a single actuator may be provided to operate multiple mobile pipe retainers.
The rotating headclamp is supported by the support frame, such that the support frame absorbs the load of the suspended drill string. Advantageously, the support frame comprises a through-passage, wherein the through passage is provided in line with the open-centered body of the rotating headclamp. Possibly, recesses are provided adjacent the through-passage, wherein in the recesses the thrust bearings are provided.
In an alternative embodiment, the support frame comprises a through-passage in which a housing of the rotating headclamp can be provided. Hence, the housing is supported by the support frame. In such an embodiment, the housing of the rotating headclamp supports the thrust bearing.
In embodiments, the thrust bearing is provided at an upper end of the rotary body. An additional bearing is advantageously provided at the bottom end of the rotary body. Possibly, these bearings are interconnected by a bearing connection. The thrust bearing may be a ball bearing, spherical roller bearing or any other suitable type of bearing.
The rotating headclamp comprises an open-centered rotary body defining a pipe passage in line with a drill string axis to allow passage of a pipe of the drill string. Hence, the body should have a diameter which is sufficient for the largest type of pipe or pipe aid to be engaged by the tubular stem. It is noticed that pipe aids are available, having a smaller diameter than the pipe to be engaged by the tubular stem, and which are thus positioned between the tubular stem and the pipe with the large diameter.
In embodiments, the pipe of the drill string is embodied as a lift sub, having a shoulder to be engaged by the pipe retainers of the rotating headclamp.
In embodiments, the open-centered rotary body is embodied as a cylinder with a flanged top end, hence in cross-section T-shaped. The flanged top end is suitable for supporting the mobile pipe retainers. Advantageously, the thrust bearing support this flanged top end of the rotary body.
The top drive unit is supported by the support frame, at least so as to absorb reaction torque from the motor of the top drive unit. A hoisting device is provided for moving the trolley up and down. It is equally conceivable that the trolley is suspended from the hoisting device, or that the support frame is suspended from the hoisting device, for example a travelling block. Hence, the support frame is suspended from the hoisting device, optionally via the trolley.
The tubular stem is to be connected to the upper end of a drill string for rotation therewith about an axis of the drill string. In an embodiment, the tubular stem is connected to or formed integral with the top drive unit. In an alternative embodiment, the tubular stem is directly connected to the support frame, in a manner allowing rotation of the tubular stem. In both embodiments, the top drive unit is allowed to engage on the tubular stem to rotate the tubular stem and thereby the connected drill string to drill the well.
At least the tubular stem is vertically movable relative to the rotating headclamp between an upper remote position allowing the engagement of a pipe by the rotating headclamp and a lower connection position allowing the attachment of the tubular stem with the pipe while the pipe and/or the drill string is supported by the rotating headclamp. In an embodiment, the top drive unit with the tubular stem is movably supported in the support frame, Alternatively, a so-called splined stem is applied and the top drive unit is supported stationary, while the stem is vertically movable. Yet alternatively, the tubular stem is provided stationary and the rotating headclamp is vertically movable relative to the tubular stem.
In an embodiment, support frame is furthermore provided with a drive for moving the tubular stem vertically and relative to the rotating headclamp between the upper remote position and the lower connection position, e.g. including a rail and trolleys or alternatively including hydraulic pistons.
Preferably, in the remote position of the tubular stem the rotating headclamp is removable from the support frame. This is advantageous e.g. in view of maintenance of the rotating headclamp, or when a different type of rotating headclamp is required to match with the pipe that is to be engaged.
In embodiments, the top drive unit is detachable from the support frame. For example, in an embodiment, the support frame supports a hook, and the top drive unit is provided with a bail so as to suspend the top drive unit from the hook. Such a detachable top drive unit enables the top drive unit to be removed from the support frame, whilst the rotating headclamp is still is fully functional. This may, e.g., be of use to conduct maintenance or repairs on the top drive unit during tripping of the drill string. The top drive unit can then simply be removed, and tripping can nonetheless be effected. In addition, it is possible to provide a substitute top drive unit, and to allow the top drive well drilling installation of the invention for an exchange of the top drive units. In an embodiment, wherein the top drive unit is detachable from the support frame a method can be carried out, comprising the following steps:
Hence, such an installation allows for an easy replacement of a top drive unit, when required. It is conceivable that the step of detaching the top drive unit is not followed by the replacement of the top drive unit, but that alternative drilling operations may follow, not requiring a top drive unit.
The top drive unit includes a tubular stem and a motor. It is conceivable that not the entire top drive unit is removed or substituted, but only part thereof. For example, the motor can be removed/replaced, while remaining the tubular stem in place. This is in particular advantageous in embodiments wherein the tubular stem is supported by/connected to the support frame.
The removal of the motor allows drilling to be followed by an operation including the use of mud hoses and the tubular stem, wherein the motor of the top drive unit has thus been removed.
The support frame is embodied as a direct drill string load bearing connection between the rotating headclamp and the trolley, independent from the top drive unit. Hence, the rotating headclamp is supported by the trolley, while the top drive unit is also supported by the trolley.
In embodiments, the support frame comprises a horizontal cross beam to support the rotating headclamp. Advantageously the length of the horizontal cross beam exceeds that of the rotating headclamp, to provide one or more storage locations for drilling equipment, such as spare or alternative rotating headclamps or parts thereof. Preferably at least two storage locations are provided at opposite sides of the rotating headclamp. In embodiments, the rotating headclamp is translatably supported by the cross beam between an operative position in line with the drill string axis and a parking position.
In an embodiment, a wrench device is provided, which is e.g. connected to the top drive unit, for making and breaking connections between the tubular stem and the drill string. Preferably, the wrench device is adapted for horizontal motion relative to the tubular stem.
In embodiments, the support frame furthermore supports a centralizer below the rotating headclamp to centralize a pipe and/or the drill string, and advantageously align it with the pipe passage defined by the rotary body of the rotating headclamp.
A hoisting device is provided for moving the trolley up and down. The hoisting device may be of a RamRig-type, or alternatively comprise a rack-and-pinion. In an embodiment, the hoisting device comprises a cable and a winch, a crown block, and a travelling block suspended from the crown block by said cable, wherein the trolley is suspended from the travelling block so as to move up and down upon operation of the winch.
In embodiments, a pipe positioning device, e.g. embodied as a pipe positioning motion am is provided to pass a pipe of the drill string in a vertical orientation through the pipe passage of the rotating headclamp, and to position a shoulder of the pipe to allow engagement of the pipe of the drill string below the shoulder by the mobile pipe retainers in the operative position thereof, wherein in particular the pipe is embodied as a lift sub.
It is conceivable that the pipe positioning device is supported by the trolley. It is likewise conceivable that the pipe positioning device is supported by the drilling tower, i.e. as a motion arm assembly as disclosed in WO2014/182160.
In embodiments, the pipe positioning device is adapted to lift 60,000 kilos. Such a pipe positioning motion arm is suitable to position a telescopic joint (60,000kg) or a bottom hole assembly (20,000kg) in the rotating headclamp. Generally, such a robust pipe positioning device is supported by the trolley. Known motion arms supported by the tower are adapted to lift up to 7000kg. However, it is also conceivable that a pipe positioning device adapted to lift up to 60,000kg is supported by the tower.
In embodiments, the pipe positioning device is adapted to receive a pipe of the drill string, in particular a lift sub, in a non-vertical orientation, in particular a horizontal orientation, e.g. from a catwalk device.
In embodiments, the pipe positioning device comprises a gripper, adapted to engage on a pipe such as a lift sub, in particular below a shoulder of the pipe or lift sub. A lift sub is a pipe portion specially designed to be added to the drill string for lifting purposes. In embodiments, the lift sub is embodied with at least one shoulder.
Advantageously, a two-shouldered lift sub is provided, comprising an upper shoulder adapted to be engaged by the pipe retainers of a rotating headclamp, and a lower shoulder adapted to be engaged by a gripper of a pipe positioning device. Preferably, the two-shouldered lift sub further comprises a pin to be engaged in a box of a drill pipe.
In an embodiment, the pipe positioning device comprises a mutually connected articulating inner and outer boom, wherein a gripper is attached to the outer boom, the gripper being adapted to engage on a pipe such as a lift sub, in particular below a shoulder of the pipe or lift sub. The inner boom can e.g. be attached to the trolley or to the drilling tower.
In a specific embodiment, the pipe positioning motion arm comprises:
The present invention further relates to a method for performing a well drilling operation, wherein use is made of the inventive installation according to the attached claims.
In a possible embodiment, in particular for the assembly of a drill string, the method comprises the steps of:
In a possible embodiment, in particular wherein a substitute rotating headclamp is provided, the method comprises the steps of:
In embodiments, the top drive unit is detachable from the support frame, and wherein a substitute top drive unit is provided, the method comprising the following steps:
In embodiments, it is required to transfer mud via a mud hose to the top drive unit. To this end, a mud connector is provided on the top drive unit. According to a possible embodiment, the support frame is provided with a frame connector for the mud hose. The advantage of a mud hose connector at the support frame is that the load of the mud hose is not only suspended from the top drive unit, but also, largely, from the support frame. As the top drive unit is advantageously movably provided in the support frame, a portion of the mud hose between the top drive unit and the mud hose connector, also referred to as the mud hose connection, is slack to compensate for movements of the top drive unit.
Different types of pipes can be handled by the top drive well drilling installation of the invention. The rotating headclamp is e.g. adapted to suspend drill pipes, drill string, casings, liners, etc. etc.
The invention is further explained in relation to the drawings, in which:
In
The top drive well drilling installation 1 is furthermore provided with a top drive unit 30 including a tubular stem 31 to be connected to the upper end 51 of a drill string 50, visible in
The trolley 12 is provided with a support frame 45 supporting the top drive unit, at least so as to absorb reaction torque from the motor of the top drive unit. In the shown embodiment, the top drive unit 30 is movably supported in the support frame 45 in a direction D, via actuators 33, between an upper remote position allowing the engagement of a pipe by a rotating headclamp 40 (explained below) and a lower connection position allowing the attachment of the tubular stem 31 with the pipe while the pipe and/or the drill string is supported by the rotating headclamp 40. In
According to a preferred embodiment of the invention, the top drive unit 30 is movable upwards to such an extent that it is remote from the rotating headclamp 40, wherein in this remote position of the top drive unit 30 the rotating headclamp 40 is removable from the support frame 45.
The top drive well drilling installation 1 is furthermore provided with a hoisting device 20 for moving the trolley 12 up and down. The hoisting device comprises a winch, not visible, and a cable 21 extending from the winch, via one or more pulleys 23 at the top of the drilling tower 10 to a crown block 24 and a travelling block 25. The crown block comprises multiple sheaves, mounted on a common axle. The travelling block 25 is suspended from the crown block 24 by said cable 21. In the embodiment shown in
The support frame 45 additionally supports a rotating headclamp 40, shown in detail in
In the shown embodiment, the rotating headclamp comprises a housing 49 supporting the thrust bearing 43, which housing is supported by the support frame 45. Alternatively, the support frame 45 supports the rotating headclamp 40 directly, e.g. via the thrust bearing 43. Either way, the support frame 45 absorbs the load of the suspended drill string.
Possibly, the support frame 45 is adapted to support more than one rotating headclamp, i.e. a substitute rotating headclamp.
Possibly, a rotating headclamp 40 is translatably supported in the support frame 45 between an operative position in line with the drill string axis A and a parking position. Thus, the drill string axis can be cleared of the rotating headclamp if so desired. In addition, it is possible to have a support frame 45 comprising two rotating headclamp which can be positioned in line with the drill string axis A as desired.
Here, the rotary body is embodied as a cylinder 41b with a flanged top end 41a supporting the mobile pipe retainers 42. The thrust bearing 43 supports the flanged top end 41a of the rotary body.
Furthermore, in the shown embodiment, an additional bearing 44 is provided at the bottom end of the rotary body 41. A bearing connection 49a, which is a static frame part optionally integrated with housing 49, connects the thrust bearing 43 at the upper side of the open-centred rotary body with bearing 44 at the bottom end thereof.
In the shown embodiment, the support frame furthermore supports a centralizer 52 below the rotating headclamp to centralize the drill string. Such centralizers are known in the art.
Furthermore, the support frame supports a wrench device 56, for making and breaking connections between the tubular stem 31 and the drill string 50.
Pipe retainers 42 are movable between a non-operative position and an operative position. In the non-operative position (not shown) the pipe retainers 42 allow passage of a pipe of the drill string through the pipe passage 41a. In the operative position as shown in
In
In the shown embodiment, the mobile pipe retainers 42 have a clamping jaw 42a to engage on a pipe or tool, which is preferably an exchangeable clamping jaw to be able to match the diameter and/ or shape to the type of pipe or tool.
In
The mobile pipe retainers 42, 42′ of
In
According to a preferred aspect of the invention, mud hose 280 is connected to support frame 245 via a mud hose connector 281. Similarly, other supply lines for electronics, control signals and hydraulics may also be connected to support frame 245 alone, e.g. via a drag chain or the like. The electronics, control signals, hydraulics and/ or mud are subsequently transferred to the top drive unit 230 via a mud hose connection 238. Here, a mud hose connection 283 is shown, transferring mud from the mud hose 280 supported by the mud hose connector 281 on the support frame 245 to the conventional mud connector 282 on the top drive unit 230. Hence, the weight of the mud hose (etc.) is no longer supported by the top drive unit, but by the support frame 245.
This mud hose connection 283 can be disconnected from the top drive unit 230 upon removal of the top drive unit 230, while mud hose 280 remains connected to support frame 245. This is advantageous e.g. during maintenance of the top drive unit, or when an alternative top drive unit is to be installed, or when the trolley and elevator are used for purposes not requiring a top drive unit.
In
It is likewise conceivable that such a pipe positioning motion arm is supported by the drilling tower, i.e as a motion arm assembly 2 as disclosed in WO2014/182160 and as visible in
In
An outer boom 63 has one end which is pivotally attached to the inner boom 61 about a horizontal second pivot axis 64, parallel to and spaced from the first pivot axis 62. The outer boom 63 is pivotable in a second rotation direction, R2, opposite to the first rotation direction R1, between a parking position in which the outer boom and inner boom are essentially parallel, as visible in
A first pivot drive, here a hydraulic cylinder 71, is mounted between said support frame 45 and said inner boom 61 and adapted to pivot the inner boom 61. A second pivot drive, here embodied as parallel hydraulic cylinders 72, is mounted between said support frame 45 and said outer boom 63, and adapted to pivot the outer boom 63. A pipe gripper drive, here embodied as two parallel hydraulic cylinders 73, is mounted between said outer boom 63 and said pipe gripper 65 and adapted to pivot the pipe gripper. The first pivot drive 71, second pivot drive 72 and pipe gripper drive 73 are adapted to operate simultaneously.
Here, inner boom 61 is provided with an end stopper 68 against which the outer boom 63 is adapted to rest in the parking position, as visible in
In
Lift sub 81 is a pipe portion specially designed to be added to the drill string for lifting purposes. The lift sub is embodied with at least one shoulder. Here, the lift sub is embodied as a two-shouldered lift sub, comprising an upper shoulder 81 adapted to be engaged by the pipe retainers of a rotating headclamp, and a lower shoulder 81b adapted to be engaged by the gripper 65 of the pipe positioning motion arm 60. Not visible is that the two-shouldered lift sub further comprises a pin which is engaged in a box 80a of drill pipe 80.
An advantage of the shown pipe positioning motion arm 60 is that the vertical positioning of the lift sub 80, as visible in
In
The top drive well drilling installation comprises a drilling tower, not shown, which is e.g. embodied as a mast with a closed contoured steel structure with at least one firing line 5 outside of the mast itself. For example the mast is arranged adjacent a moonpool of a drilling vessel, or over a larger moonpool with two firing lines along opposed outer faces of the mast as is known in the art.
In an alternative design the drilling tower is embodied as a derrick with the firing line within the structure of derrick, e.g. the derrick having a lattice structure placed over the moonpool.
The mast, not shown per se, is provided at the side of the drill floor and is provided with two parallel vertical trolley rails 111a, 111b. A trolley 112 is guided along said trolley rails 111a, 111b.
A top drive unit 130 is attached to the trolley 112.
The top drive unit 130 comprises in this example four electric top drive motors 132a, 132b, 132c, 132d which commonly drive, via gearbox or transmission housing 135, a rotary stem or quill 131. As known in the art the quill 131 is connectable, e.g. via a threaded connection, e.g. via a saver sub, to the top end of a drilling tubular aligned with the firing line. Thereby the top drive unit 130 is able to impart rotary motion and drive torque to a drilling tubulars string.
A main hoisting device 120 is provided that is adapted to move the trolley with the top drive unit up and down along the vertical trolley rails 111a, 111b. For example the trolley and hoisting device have sufficient strength and capacity to handle a load of 1000 tons or more in the firing line.
The trolley 112 is provided with a rigid support frame 145 supporting the top drive unit 130, at least so as to absorb reaction torque from the motor of the top drive unit.
The rigid frame structure 45 with upper and lower trolley beams 145a, 145b that each have at each end thereof rollers engaging the respective trolley rail 111a, 111b on the mast. These beams 145a, 145b here have about a V-shape in top view. These beams 145a, 145b support here a single vertical rear frame member 145c, that embodies sort of a spine of the trolley 112 and that spans the height between the beams 111a, 111b.
This rear frame member 145c is provided with one or more, here a pair of parallel, vertical guide rails 160a, b. The top drive unit 130 is provided with a chassis 130a with rollers 130b or other guide members that cooperate with said guide rails 160a, b.
This rear frame member 145c may be embodied as a box girder.
From the top end of said rear frame member 145c a forward cantilevered frame member 145d extends, away from the mast. At its forward end this frame member 145d carries a transverse horizontal top frame member 145e, generally in a transverse imaginary plane that encompasses the firing line (not shown).
The top frame member 145e is provided with connectors, here holes, for connecting thereto a series of cable sheaves 121 in a side by side arrangement. The hoisting device 120, as a crown block, is also provided with cable sheaves so that the trolley 112 is suspended by one or more winch driven cables in a multiple fall arrangement.
The support frame 145 further comprises left and right frame members 145x, 145y which are suspended from the transverse horizontal top frame member in a transverse plane that encompasses the firing line. As depicted these left and right members 145x, 145y are directly and pivotally connected to the frame member 145e, here pivotal about an axis perpendicular to said transverse plane. As is preferred each left and right member 145x, 145y has an upper eye, as here through two spaced apart tabs, with a pin being secured through said eye and through a hole in the frame member 145e.
A rotatable head clamp assembly carrier 161 is connected, as is preferred releasably, with hooks 161b to lower ends of said left and right members 145x, 145y. The carrier 161 supports, here is integrated with, a rotatable head clamp assembly 162 of which an example is depicted in
As discussed the vertical guide rails 160a, 160b guide the top drive unit 130 as the rollers 130a, 130b of the chassis 130a ride along said rails 160a, b.
In this embodiment, as preferred, the same guide rails 160a,b also guide the carrier 161, here a guidance portion 161a thereof. Also, as preferred, the same guide rails 160a, b guide a wrench and/or clamping device 190, which will be discussed later.
In addition to guiding said components, the one or more guide rails 160a, b here, as is preferred, also serve the purpose of absorbing any reaction torque that is caused by operation of the installation on the respective component and transmit said torque to the frame 145.
Between the top drive unit 130 and the trolley frame 145 there are one or more vertical displacement actuators 140 so that the top drive unit 130 is vertically mobile relative to the frame by said one or more vertical displacement actuators, here adapted to perform controlled lowering and raising of the top drive unit during make up or breaking of the threaded connection between the quill or rotary stem on the one hand and the tool joint or box member of the tubular suspended from the rotatable head clamp assembly on the other hand.
The trolley is provided with an auxiliary hoisting device 180 that is adapted to vertically move at least the top drive unit 130, here also the device 190, relative to the frame. It is depicted that the device 180 includes a chain hoist device, with a hook that can be coupled to either the top drive chassis 130a or the device 190 as shown in
Reference numeral 190 indicates a wrench and/or clamp device that allows to retain the tool joint or box member held by the assembly 162 when make-up or break-up of a threaded connection is performed.
In
The pipe positioning device 260 is supported by the hooks 161b of the carrier 161, which are connected to lower ends of said left and right members 145x, 145y. The carrier 161 supports, here is integrated with, a rotatable head clamp assembly 162.
The pipe positioning device 260 is provided to allow a pipe 270 of the drill string to pass in a vertical orientation through the pipe passage of the rotating headclamp, and to position the shoulder of the pipe to allow engagement of the pipe of the drill string below a shoulder by the mobile pipe retainers in the operative position thereof.
Here, a lift sub 271 is attached to pipe 270 of the drill string. Lift sub 271 is a pipe portion specially designed to be added to the drill string for lifting purposes. The lift sub is embodied with at least one shoulder. Here, the lift sub is embodied as a two-shouldered lift sub, comprising an upper shoulder 271a adapted to be engaged by the pipe retainers of a rotating headclamp, and a lower shoulder 271b adapted to be engaged by a gripper of the pipe positioning device.
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Number | Date | Country | Kind |
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2015604 | Oct 2015 | NL | national |
2015605 | Oct 2015 | NL | national |
2016971 | Jun 2016 | NL | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NL2016/050698 | 10/7/2016 | WO | 00 |