FIELD OF THE INVENTION

The present invention relates to a tubular handling mechanism for a hydraulic workover unit configured for performing well operations, in particular to a tubular handling mechanism for a snubbing unit, and to an assembly of such a unit with a tubular supply unit.

BACKGROUND OF THE INVENTION

Hydraulic workover units are widely used for well maintenance and interventions, such as running and retrieving pipes to perform fishing, milling, pumping or any other downhole operation. These units may reach heights up to 10 metres, or even more, dependent on the cavity which is required for staging in bottom hole assemblies during operations. In the case of live well operations, wherein the well is still pressurized, the hydraulic workover unit is a snubbing unit comprising blowout-preventers, thus increasing the size of the unit even more: snubbing units may reach up to 15 metres or higher. In conventional hydraulic workover units, the unit is placed over a well and pipes are hoisted to the top of a hydraulic workover unit, where a working platform is arranged. The operating personnel on the working platform must then manoeuvre and guide the hoisted pipes above the pipes already present, after which the pipes are connected and forced into the well by a jack. Hoisting of the pipes to the top of the hydraulic workover unit is performed by an external crane, a gin pole counterbalance winch system (including guywires and deadweights for wind loads) or a derrick. During operations, these hoisting systems grab a pipe which is stored on ground level by its upper end and hoist the tubular upwards until the bottom end of the tubular has reached workers on a working platform on top of the hydraulic workover unit, and vice versa.

These conventional systems thus require operators to work on top of a possibly pressurized well, on a small working platform surrounded by heavy moving machinery, high pressure hoses and possibly underneath a load. Generally, three workers are required on the working platform during standard operations. In case of a blowout during live well operations, even with emergency egress systems, operators are put in harm’s way. In addition, these external cranes or gin pole counterbalance winch systems are required to be at least the height of the tubular length on top of the hydraulic workover unit, which may amount to well over 20 metres. The enormous size and weight of the machinery that is required during operations can be a major disadvantage, especially during operations in relatively tight spaces such as small satellite platforms.

There are some alternative ways known in the art of drilling to supply rods to a drilling head. LIS2010/0021721 A1 for example relates to an accessory for a drill rig used in drilling bore holes. The drill rig has an upstanding mast to which a support member is connected. Handling means supply drilling rods in a horizontal position from a storage zone to the support member, which support member rotates the rod to a vertical position above the drill string, after which the rod is engaged by a drive head which enables the rod to be engaged with a drill string that is located in the bottom of the mast. As such, there is no crewmember needed to manipulate and support the drill rod in its movement between the storage zone and the drill string.

Unfortunately, a system according to US2010/0021271A1 is impractical for use for hydraulic workover unit or snubbing units. The handling means are required to provide the drilling rods from the storage zone in a horizontal position. In the case of hydraulic workover unit or snubbing units, which can reach up to 10 or 20 metres heigh, the storage zone would be required to be positioned at such heights as well, which would require large and heavy equipment and the use of a derrick.

WO2016/167632 discloses another rod mounting device for a drilling machine which supplies the drill rod in a horizontal position to a rod clamp unit. The rod clamp unit rotates the drill rod to a vertical position, after which the drill rod is grabbed by a drill head. Supply of the drill rod is achieved by a rod supply unit, which elevates a rod in a horizontal state from where it is supplied to the rod clamp.

Similarly as to US2010/0021271A1, a system according to WO2016/167632 cannot be used for hydraulic workover unit or snubbing units: the rod supply unit would have to elevate the rods up to 20 metres high, which would require additional heavy equipment.

DESCRIPTION OF THE INVENTION

The present invention aims to overcome the above disadvantages at least partly or to provide a usable alternative. In particular, the present invention aims to provide a hydraulic workover unit which comprises more compact equipment for hoisting tubulars.

Another object of the present invention is to provide a hydraulic workover unit which can be operated with less manual effort.

In a first aspect, the present invention provides a hydraulic workover unit configured for performing well operations, comprising a supporting structure configured to be arranged above a well head; a tubular handling mechanism connected to the supporting structure and configured for positioning a tubular in an upright position above the well head, wherein in the upright position the tubular has an upper end facing substantially upwards and a bottom end facing substantially downwards, a jacking system mounted to the supporting structure and arranged below the tubular when in the upright position, wherein the jacking system is configured for applying a load on the tubular in at least an axial direction; wherein the tubular handling mechanism is configured for engaging the tubular in a supply position wherein the bottom end of the tubular is positioned upwards relative to a horizontal plane, and for displacing, including tilting, the tubular to the upright position, and vice versa.

The hydraulic workover unit according to the invention may be used for dead well operations, or it may be converted to a snubbing unit by including extra blowout preventers to perform live well operations. The hydraulic workover unit comprises a supporting structure configured to be arranged above the well head. The supporting structure is for example an externally prepared structure resting on the earth around the well head to support the hydraulic workover unit, or a blowout-preventer or a jacking system structure when the hydraulic workover unit is solely supported by the well head. Connected to the supporting structure is a tubular handling mechanism, which is configured for positioning a tubular in an upright position above the well head, such that the tubular has a upper end facing substantially upwards and a bottom end facing substantially downwards. In this upright position, the tubular is positioned above a jacking system which is also arranged above the well head. This jacking system is preferably hydraulically driven, or alternatively pneumatically or electrically driven, and is configured for applying a load on the tubular in at least the axial direction of the tubular, to force the tubular into the well head or to retrieve the tubular from the well. In addition, the jacking system may also be configured for providing a torsional load on tubulars. Hence, in the case of threaded tubulars the jacking system may also be configured for rotating, and therefore tightening or loosening tubulars.

To position tubulars above the well head, the tubular handling mechanism is configured for engaging the tubular in a supply position and for displacing, including tilting, the tubular to the upright position. In the reverse process, the tubular handling mechanism tilts the tubular from the upright position to the supply position, from which the tubular is released. In the supply position, the bottom end of the tubular is positioned upwards relative to a horizontal plane. This inclined position of the tubular in the supply position enables efficient supply of the tubulars from a low height, such as from ground level to the height where the tubular is eventually required during well operations. The top of the pipe thus does not have to be lifted to above the top of the hydraulic workover unit by a crane or gin pole as done in conventional systems, which systems therefore are required to be at least the height of the hydraulic workover unit plus the tubular. Instead a tubular supply unit may be used to supply tubulars from ground level to the supply position that is smaller in terms of size, weight and power. This supply of tubulars at an angle with the bottom end upwards thus advantageously eliminates the need for large, high and heavy equipment such as cranes, gin poles or horizontal tubing lifting machinery. The whole system and value chain of operations therefore becomes more compact, simpler, and safer.

Moreover, assembly of the hydraulic workover unit with a tubular handling mechanism according to the invention is more convenient. Large and heavy cranes (which need to be recertified regularly) are required during the assembly phase of conventional hydraulic workover units, especially for installing e.g. the gin pole counterbalance system. After assembly of the hydraulic workover unit these cranes are either not used or dismantled. As the overall height of a hydraulic workover unit with a tubular handling mechanism according to the invention is much less, the hydraulic workover does not require the use of these larger cranes during assembly and installation. This is especially advantageous for offshore operations where cranes are not always present or are limited in capacity, and also provides advantages in terms of sustainability as no less heavy machinery is required to be transported to the platforms. .

In addition, the tubular handling mechanism has the advantage that, after tilting, the tubular is immediately in or close to the upright position. It may only be required to perform a translational or rotational movement of the tubular after tilting, to ensure that the tubular is in the correct upright position above the well head. These movements are preferably automated. The need for operators which manually position the tubular in the correct position is thereby eliminated. A hydraulic workover unit with a tubular handling mechanism according to the invention therefore requires less or no more operators to be present on the working platform . This is especially advantageous during operations on small satellite platforms, where a restriction on the maximum number of persons on board (POB) is in place and deck space is limited, which may provide a bottleneck to the speed and efficiency of operations.

The tubular handling mechanism can also advantageously be used for the removal of cut or severed cemented casings. In conventional systems, these old pieces of tube retrieved from wells are heavy and have no lifting points. It is therefore required to mill holes in them after they have been pulled out of the well, and a hoisting device is placed in these holes to bring it from the well to ground level. The hydraulic workover unit with tubular handling mechanism according to the invention is instead configured for engaging the tubular, which eliminates the need for milling holes. The engaging means, such as clamps are then preferably configured for carrying heavy loads.

The tubular handling mechanism may optionally comprise well control apparatus configured for automatically closing tubulars in the case of blowouts. A well control apparatus is for example a hydraulic feature, such a hydraulic well control valve, e.g. a full opening safety valve, a stabbing valve or an inside blowout preventer, with which a tubular can be closed from a distance. In conventional systems, these valves are closed manually by operators present on the working platform, which puts them at great risk of harmful accidents.

In an embodiment of the invention, the bottom end of the tubular in the supply position is positioned at an angle of at least 10° upwards relative to the horizontal plane. The angle at which the tubular is supplied may vary with the height of the hydraulic workover unit. In the case of relatively small hydraulic workover units, a supply angle of at least 10°, such as 20° or 30° may be sufficient to realize the above mentioned advantages. In the case of large hydraulic workover units, and especially in the case of snubbing units, which have an increased height due to the blowout-preventers, a larger supply angle might be preferred, such as an angle of at least 20°, 30°, 40°, 50°, 60° or 70°. In exceptionally high hydraulic workover units a supply angle of maximally 85° might be required.

In an embodiment of the invention, the tubular handling mechanism is configured for tilting the tubular over an angle of at least 100°, preferably at least 120°, and more preferably at least 140° from the supply position to the upright position. The tilting angle may again depend on the height of the hydraulic workover unit. For example, in the case of smaller hydraulic workover units, a lower tilting angle in the range of 100-130°, such as 110-120°, may be favored. In the case of larger hydraulic workover units, such as snubbing units, a tilting angle in the range of 120-170°, such as 130-160°, may be favored. The tilting angle is preferably maximally 175°.

In a preferred embodiment of the invention, the tubular handling mechanism comprises a jib arm which is pivotably mounted around a horizontal axis to the supporting structure. The jib arm is pivotable between a supply configuration wherein the jib arm is substantially parallel to the tubular in the supply position and an operation configuration wherein the jib arm is substantially parallel to the tubular in the upright position. The jib arm comprises engaging means configured for engaging the tubular, such as one or more clamping devices or one or more grippers. The jib arm is a relatively small apparatus which requires minimal space on the hydraulic workover unit, while also being able to tilt the tube over a wide angle to easily move the tubular to the top of the hydraulic workover unit. The range over which the jib arm is pivotable is preferably preset at a fixed range such that the movement of the jib arm is automated, and the supply position and upright position are fixed. When the jib arm engaging a tubular is pivoted to the operation configuration, the tubular is in the tilted position, which is either the same as the upright position or it may be required to perform an extra operation, such as a translation or a rotation, to move the tubular from the tilted position to the upright position, or vice versa. In a preferred embodiment of the invention, the jacking system of the hydraulic workover unit comprises a pipe makeup (and breakout) assembly, such as a tong assembly or a bucking unit, configured for connecting and disconnecting tubular couplings or joints. The assembly can be chosen from known device, generally comprising at least a tong member, such as a backup tong, for engaging the tubular and a torque member, such as a rotary table or a power tong, for applying a torsional load on the tubular. The torque member is generally driven by known rotational drive mechanisms, such as a hydraulic or electrical slew drive. The pipe makeup and breakout assembly is preferably arranged within the jacking system, such as a part of the pipe makeup and breakout assembly being arranged between a stationary and a traveling slip of the jacking system. Advantageously, the use of such an integrated pipe makeup and breakout assembly eliminates the need for an operator who manually attaches an external tong to the tubulars for threading. The assembly, in particular tong member, preferably comprises a compensation system, e.g. of a spring type, which enables the tubular to be moved slightly upwards or downwards during the threading of the tubular with a bottom tubular.

In an embodiment of the invention, the torque member of the pipe makeup assembly is formed by the traveling slip of the jacking system. The traveling slip is then configured for applying both an axial load as week as a torsional load on the tubular. Thus advantageously, no separate torque member is required to rotate the tubular which advantageously reduces the costs of the machinery. The backup tong is preferably arranged between the stationary and the traveling slip.

The jib am generally extends between a first end which is mounted to the supporting structure and a second end. In the operation configuration, the second end is pointing substantially upwards, and in the supply configuration the second end is pointing downwards. The jib arm is preferably extendable in the longitudinal direction of the jib arm, e.g. by a telescopic extension mechanism.

The jib arm may also advantageously be used to install wireline or coiled tubing which are for example used to determine the condition/integrity of the cement behind the casings in dismantling processes, or any other intervention, such as plug setting, logging or perforating. In conventional hydraulic workover units, a separate crane is required for installing the wireline or coiled tubing, and when having a gin pole present, it should be moved away as it forms an obstruction. The jib arm, on the other hand, is an efficient and compact alternative that eliminates these disadvantages.

In an embodiment of the invention, the jib arm in the supply configuration is positioned at an angle of at least 100°, preferably of at least 120° relative to the operation configuration.

The jib arm is preferably a fly jib configured for pivoting over an angle of up to 210° to provide a compact configuration usable e.g. during transportation. The fly jib may even be stored within the hydraulic workover unit itself during transportation. The fly jib arm comprises a jib arm base with which the jib arm is mounted to the jacking structure. The jib arm is with the first end pivotably mounted to the jib arm base and has a second free. For pivoting over an angle of up to 210° the jib arm comprises a pivot cylinder which has a fulcrum at which two lever members are engaged, wherein a first lever member also engages the first end of the jib arm and a second lever member also engages the jib arm base. When the pivot cylinder extends, the lever members are moved and the jib arm as thereby rotated around the horizontal axis.

In a preferred embodiment of the invention, the engaging means, such as the one or more clamping devices or grippers, are configured for rotating the tubular around an axis substantially perpendicular to the axis of the jib arm. When the jib arm is in the operation configuration, it might be required to rotate the tubular around a second horizontal axis from the tilted position to the upright position, or vice versa.

In an alternative or additional embodiment of the invention, the engaging means comprises an extension mechanism to enable a translation movement of the tubular. The engaging means may for example be extendable by means of a scissor mechanism to translate the tubular such that the tubular is moved from the tilted position to the upright position, or vice versa.

In an embodiment of the invention, the engaging means are rotatably mounted to the jib arm around a rotation axis parallel to the longitudinal axis of the jib arm. In addition, the engaging means may be configured for engaging at least two tubulars and/or for engaging at least a tubular and a well control apparatus, or for engaging at least three objects, such as two tubulars and a well control apparatus. The engaging means are preferably two grippers rotatably mounted opposite of each other to the jib arm. The engaging means may for example be configured for engaging a regular pipe and a wash pipe which is used to recover a stuck pipe, debris or lost equipment. In conventional constructions, where only one tubular is lifted to or from the hydraulic workover unit, the handling of the washier pipe requires additional operations: a tubular which is held by the gin pole or the external crane should be lowered, the wash pipe should be picked up and transported back and from the workover unit, and the tubular should afterwards be picked up and transported. It is furthermore required to attach and re-attach the pump hose and hydraulically actuated well control valve, and the connection must be pressure tested each time. When the hydraulic workover unit instead comprises a jib arm with rotatably mounted engaging means configured for engaging at least two tubulars, the wash pipe may be present on the jib arm at all times. To transport the wash pipe to the top of the hydraulic workover unit therefore only requires rotation of the engaging means. Additionally or alternatively to the wash pipe, the engaging means may engage a well control apparatus configured for closing off the well in the case of a blowout without the requirement of manual operations. Such a well control apparatus is for example a valve which may be hydraulically driven, e.g. a full opening safety valve, a stabbing valve or an inside blowout preventer. Such a well control feature is preferably present on the wash pipe. The well control apparatus comprises for example a stabbing valve which is controlled via suitable control lines and which is positioned on top of the wash pipe. The valve is via a pump inlet connected a pump hose. In the case of a blowout, the rotatable engaging means are rotated to position the wash pipe above the well head, after which the valve can be closes from a distance via the suitable control lines.

Besides their use on the jib arm as disclosed in the present invention, these rotatable engaging means may also be used for other applications.

In an alternative embodiment of the invention, the tubular handling mechanism comprises a central passage axis configured for receiving and engaging the tubular, wherein the tubular handling mechanism is pivotably mounted to the supporting structure around a horizontal axis between a supply configuration wherein the central passage axis is substantially coaxial with the axial direction of the tubular in the supply position, and an operation configuration wherein the central passage axis is substantially coaxial with the axial direction of the tubular in the upright position. During supply of the tubular, the tubular handling mechanism adopts the supply configuration. The central passage of the tubular handling mechanism may then receive a tubular which has a bottom end upwards relative to a horizontal plane. The tubular handling mechanism is configured for engaging the received tubular. When engaged, the tubular handling mechanism is pivoted to the operation configuration such that the tubular is tilted to the upright position, or vice versa.

In an embodiment of the invention, the tubular handling mechanism having a central passage is pivoted at an angle of at least 100°, preferably at least 120°, more preferably at least 140° relative to the operation configuration.

In an embodiment of the invention, the tubular handling mechanism having a central passage is configured for applying a load on the tubular in at least a radial direction. The tubular handling mechanism may for example be a drive system, such as a rotary table. The tubular handling mechanism is then configured for rotating, and therewith tightening or loosening tubulars. Such a rotary table can drive a tubular at the periphery of the tubular and therefore does not need to engage at the top of the tube, which decreases the height of the hydraulic workover unit.

In an additional or alternative embodiment of the invention, the tubular handling mechanism having a central passage is, in the operation configuration, moveable back and forth along the central passage to apply a load on the tubular in the axial direction. The tubular handling mechanism is for example a part of the jacking system configured for inserting or retrieving tubulars into or from a well. Preferably first hydraulic cylinders are provided between the frame and the tubular handling mechanism for moving the tubular handling mechanism backwards and forwards.

In an embodiment of the invention, a chuck is arranged between the tubular handling mechanism and the frame, wherein the chuck is moveable back and forth in the axial direction of the tubular. The chuck may be used to apply an additional axial load on the tubular during running tubulars into or retrieving tubulars from a well. Preferably second hydraulic cylinders are provided between the frame and the chuck.

The tubular handling mechanism as described above can also be used in drilling rigs. Drilling rigs do however require a mast for the heavy pulling and pushing of rods. Although the tubular handling mechanism may provide advantages by eliminating heavy machinery for rod handling and in terms of efficiency of the positioning of the rods, the height of the drilling rig will likely remain unchanged due to the required mast.

In a second aspect, the present invention relates to an assembly for well operations, comprising a hydraulic workover unit according to any one of the preceding claims and a tubular supply unit, wherein the tubular supply unit is configured for engaging the tubular in a substantially horizontal or vertical position and for displacing, including tilting, the tubular from the horizontal or vertical position to the supply position, and vice versa.

In the horizontal or vertical position, the tubular is generally stored in a storage space on or near ground level. This is for example a storage rack or a fingerboard. The tubular supply unit then engages the tubular when in the storage zone and displaces, including tilting, the tubular to the supply position, from where the tubular is engageable by the tubular handling mechanism. Advantageously, the tubular supply unit is therefore only required to engage the tubular and position it in the supply position, but it is not required to lift the tubular all the way up to the top of the hydraulic workover unit from where the jacking operations are performed. Thus advantageously, a tubular supply unit may be used that is smaller in terms of size, weight and power, which has many advantages with regard to the transport and use of the equipment. As mentioned before, the overall height of the system is much less compared to conventional systems. Moreover, the footprint of an assembly according to the invention is smaller, as the tubular supply unit can be positioned closer to the hydraulic workover unit compared to conventional counter-balance winch systems or cranes, which is especially advantageous during offshore operations on (satellite) platforms.

The tubular supply unit may be any conventional (relatively light weight) supply unit, such as a telescopic handler, a flat mounted crane or a truck mounted crane.

BRIEF DESCRIPTION OF THE DRAWINGS The invention shall now be explained in more detail below by means of describing some exemplary embodiments in a non-limiting way with reference to the accompanying drawings, in which:

Fig. 1 depicts an embodiment of a snubbing unit with a jib arm according to the invention;

Fig.2 depicts an assembly of a hydraulic workover unit and a tubular supply unit according to the invention;

Fig.3A-D depict an embodiment of a hydraulic workover unit with a jib arm according to the invention;

Fig. 4 depicts an hydraulic workover unit with a fly jib according to the invention;

Fig. 5 depicts an embodiment of a jacking system with a tong assembly on a hydraulic workover unit according to the invention;

Fig. 6 depicts a jib arm with rotatable engaging means on a hydraulic workover unit according to the invention;

Fig. 7 depicts a hydraulic workover unit according to the invention during operations on a small satellite platform;

Fig. 8 depicts an embodiment of a snubbing unit with a rotary table as tubular handling mechanism according to the invention;

Fig. 9 depicts a detailed version of the rotary table from Fig. 8 according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In Fig 1. the hydraulic workover unit, in this embodiment a snubbing unit, is in its entirety denoted with reference number 2. The snubbing unit comprises a stack of blowout-preventers 4 which are positioned above a well head 6, with an annular blowout-preventer 8 positioned at the top of the stack 4. The height of the blowout-preventers 4 is dependent on the amount of cavity which is required during operations, and for snubbing units may amount up to 10 or 15 meters. A jacking system 10 configured for applying at least an axial on a tubular is mounted on top of the blowout-preventers 4. The jacking system 10 comprises a jacking structure 12, a stationary slip 14 and a traveling slip 16 which are hydraulically driven using hydraulic cylinders 17 when forcing a tubular in the well head 6 or when retrieving a tubular. A supporting structure 18 further supports the hydraulic workover unit 2.

Mounted to the jacking structure 12 is a tubular handling mechanism, in this embodiment a jib arm 20. The jib arm 20 is configured for pivoting over an angle of 210°. Due to this large pivoting range the fly jib can be stored compactly in the hydraulic workover unit 2. The jib arm 20 is pivotably mounted to the jacking structure 12 around a horizontal axis and extends between a first end 22 which is connected to the jacking structure 12 and a second end 24, which is a free end. The jib arm 20 in Fig. 1 is in a supply configuration, which means the jib arm 20 is substantially parallel to a tubular 26 which is in a supply position, i.e. with a bottom end 28 of the tubular upwards relative to a horizontal plane. The jib arm 20 comprises a gripper 30 as engaging means which is mounted to the jib arm 20. The tubular 26 is supplied in the supply position to the jib arm 20 by a supply unit. When the jib arm 20 engages the tubular 26, the jib arm 20 is pivoted to an operation configuration, thereby tilting the tubular 26 to an upright position such that an upper end 32 of the tubular 26 is facing substantially upwards and the bottom end 28 of the tubular 26 is facing substantially downwards. When a snubbing unit is used for operations, the angle over which the tubular 26 is tilted is preferably up to 150° or even 160°. The jacking system 10 further comprises a tong assembly for connecting or disconnecting tubulars, having a tong member, such as a backup tong 34 and a rotational drive mechanism 36 which drives a rotational movement of the traveling slip 16 used to apply a torsional load on the tubular 26. As such, the tubular 26 is rotated around its longitudinal axis for connecting or disconnecting the tubular 26 from a bottom tubular (not shown).

The jib arm 20 is also configured for the reverse movement: after the jacking system 10 has retrieved a tubular 26 from the well, the jib arm 20 engages the tubular 26 in the upright position, after which the jib arm is pivoted to the supply configuration, from where it can be taken over by the supply unit (not shown).

Fig. 2 shows an assembly of the hydraulic workover unit 2 with a supply unit 37, in this embodiment a flat mounted crane. The flat mounted crane comprises an arm 38 with a clamp 39 that engages the tubular 26. The engaged tubular 26 is in a supply position with the bottom end 28 facing upwards relative to a horizontal plane. When the jib arm 20 of the hydraulic workover unit 2 the tubular 26 is released by the clamp 39 of the flat mounted crane 37 and the tubular 26 can be tilted to the upright position.

Fig. 3A-D show the displacement of the tubular 26 from the supply position to the upright position. In Fig. 3A, the second end 24 of the jib arm 20 is pointing downwards such that it can engage the tubular 26 in the supply position, i.e. with the bottom end 28 of the tubular 26 upwards relative to a horizontal plane. The jib arm 20 is pivoted over an angle a around a horizontal axis until the second end 24 of the jib arm 20 is pointing substantially upwards (see Fig. 3B). During pivoting of the jib arm 20, the engaged tubular 26 is tilted over an angle a as well. To then position the tubular 26 in the upright position, the gripper 30 on the jib arm 20 is configured for rotating the tubular 26 over an angle around an axis perpendicular the longitudinal axis of the jib arm 20 until the tubular 26 is in the upright position with the bottom end 28 of the tubular is facing substantially downward and the upper end 32 of the tubular 26 facing substantially upwards, as shown in Fig. 3C. When the tubular 26 is in this upright position, the traveling slip 16 of the jacking system 10 moves upwards and engages the tubular 26 (as shown in Fig. 3D) and the tubular 26 is ready to be connected to a bottom tubular (not shown). Preferably, the gripper 30 stabilizes the tubular 26 during connection to a bottom tubular (not shown). Alternatively, the jib arm 20 may also retract to lower the tubular 26 after which the tubular 26 is engaged by the jacking system 10.

Fig. 4 shows a jacking system 10 with a jib arm 20 in a transportation configuration during transportation of the hydraulic workover unit 2 to or from an operation site. The jib arm 20 comprises a jib arm base 40 with which the jib arm 20 is mounted to the jacking structure 12. The jib arm 20 is with the first end 22 pivotably mounted to the jib arm base 40 and has a second free end 24 which extendible in the longitudinal direction of the jib arm 20 by a telescopic extension mechanism 42. The jib arm 20 comprises a pivot cylinder 44 with which the jib arm 20 is pivoted around the horizontal axis. The pivot cylinder 44 has a fulcrum 45 at which two lever members 46, 47 are engaged, wherein a first lever member 46 also engages the first end 22 of the jib arm 20 and a second lever 47 member also engages the jib arm base 40. When the pivot cylinder 44 extends, the lever members 46, 47 are moved and the jib arm as thereby rotated around the horizontal axis, enabling the jib arm 20 to pivot over an angle of up to 210°. Due to this large pivoting range the jib arm 20 can be stored compactly in the hydraulic workover unit 2 during transport.

Fig. 5 shows a detailed version of the mechanism for providing a torsional load on the tubular 26 as depicted in Fig. 1. The backup tong 34 is positioned within the jacking structure, this backup tong 34 being configured for rotating the tubular 26 around the longitudinal axis of the tubular 26. As such, that the tubular 26 may be connected to or disconnected from a bottom tubular. The backup tong 34 is driven by a rotational drive mechanism 36, such as a hydraulic or electrical slew drive, which is in this embodiment positioned below the traveling slip 16 of the jacking system 10. The, such as a backup tong 34 comprises a compensation system, e.g. of a spring type, which enables the tubular 26 to be rotated and simultaneously to be moved slightly upwards or downwards during the threading of the tubular 26 with a bottom tubular (not shown).

Fig. 6 shows a jib arm 20 having rotatable engaging means 30 which are rotatable around the longitudinal axis of the jib arm 20. The rotatable engaging means 30 in this embodiment consist of two grippers 50, 52 which are rotatably mounted opposite of each other to the jib arm 20. Each gripper 50, 52 is configured for engaging a tubular 26, such as a general pipe and a wash pipe 54. The wash pipe 54 may therefore be present on the jib arm 20 at all times. Instead of picking up and transporting the wash pipe 54 to the hydraulic workover unit 2 when required, the rotatable engaging means 30 are rotated and the wash pipe 54 is in position. The wash pipe 54 preferably also comprises a well control apparatus 56 which is shown in more detail in the figure. The well control apparatus 56 comprises of a valve 58, preferably a hydraulic valve such as a stabbing valve, which is controlled via suitable control lines 60 and which is positioned on top of the wash pipe 58. The valve 58 is via a pump inlet 62 connected a pump hose 63. In the case of a blowout, the rotatable engaging means are rotated to position the wash pipe 54 above the well head and to close the valve 58 from a distance via the suitable control lines 60. This eliminates the need for manual closing of the well during a blowout and greatly increases the safety of the operators.

Fig. 7 shows an embodiment of the hydraulic workover unit 2 according to the invention during offshore operations on a small satellite platform 64. A flat mounted crane 37 supplies the tubulars 26 to and from a vertical storage rack 66, or a fingerboard. The hydraulic workover unit 2 according to the invention is especially suitable for operations on these satellite platforms 64 as there is often a maximum on the persons on board (POB) in force, and the hydraulic workover unit 2 advantageously requires less operators during operations. A clamping device 39 is needed on the flat mounted crane 37 to receive tubulars from the jib and manoeuvre to store away vertically in fingerboards.

Fig. 8 shows another embodiment of the hydraulic workover unit 2 according to the invention. The hydraulic workover unit 2 comprises a jacking system 10 positioned on top of blowout-preventers 4. The top port of the jacking system 10 is a rotary table 68 which is pivotably mounted to the jacking structure 12. The rotary table 68 is configured to pivot over an angle a between a supply configuration and an operation configuration, and the rotary table 68 comprises a central passage configured for receiving a tubular 26. When in the supply configuration, a tubular supply unit 37, such as a telescopic handler can insert a tubular 26 in a supply position (with the bottom end upwards relative to a horizontal plane) into the central passage of the rotary table 68. The rotary table 68 may then engage the tubular 26, after which the telescopic handler releases the tubular 26. The rotary table 68 engaging the tubular 26 is pivoted from the supply configuration to an operation configuration over an angle a, such that the tubular is positioned in the upright position above the well head 6. The rotary table has a radial clamping device with which the tubular 26 can be engaged and with which the torsional load is applied to the tubular 26.

Fig. 9 shows the upper part of the hydraulic overwork unit 2 in more detail. The rotary table 68 is partly tilted over the horizontal axis 70. The rotary table 68 has a central passage 72 into which the tubular is inserted. On the rotary table 68 there is a clamping device 74 with which the tubular can be clamped and the rotation of the rotary table 68 can be transferred to the tubular. The rotary table 68 is guided in a telescopic guide 76, 78 and can be moved up and down by first hydraulic cylinders 80 relative to a chuck 82.