TECHNICAL FIELD OF THE INVENTION

The present invention relates to a tool and method for locating connector hubs of subsea flowlines to enable a clamping device to be fitted thereto.

BACKGROUND OF THE INVENTION

Subsea flowlines, also referred to as jumpers, convey oil and gas between well heads to other subsea structures at depths of up to several kilometres below sea level . When working in vast sea depths or in situations where the multiple well heads are in production, it is necessary to deploy multiple interconnected flowlines. The interconnection of flowlines is typically provided by diverless connector systems comprising co-operating connector hubs at the terminating ends of each flowline that are clamped together. The task of locating connection hubs in mating relationship is fraught with risks that can result in subsea structures and the connector hubs being damaged, which in turn seriously disrupts or delays production for substantial periods .

To facilitate the alignment of connector hubs, recoverable machinery commonly referred to as a running tool is used to deploy the connector hub of a flowline in mating relation with another connector hub previously installed to a subsea structure. A function of the running tool is to provide a coarse level of alignment of the connector hubs. A finer level of alignment of the connector hubs is provided by the shape and formation of the mating surfaces of the connector hubs.

Remotely operated vehicles (ROVs) controlled by personnel from the surface are typically used to: i) monitor the progress of the running tool, ii) assist in manoeuvring the running tool if required, and iii) finally install clamping mechanisms to secure the connector hubs in a sealed mating relationship.

There are a number of different types of the running tools currently in use. One type of running tool is a cylindrical shaped tool that carries the connector hub and flowline to be installed. The size of the tool is scaled according to the size of exterior of the hub being installed and has a substantial mass, often greater than 2 or more tonnes and in some cases , approximately 5 tonnes . The tool is precisely lowered into position using tie lines controlled by cranes on vessels at sea level and ROVs in the vicinity of the installation. When lowered into position, the tool is secured, for example by means of lugs, to a tie-in-porch. Characteristics of the tool that, in our view, make the tool less favourable include: the tool being a dedicated tool capable only of installing specific sized connector hubs; and the tool have a very large mass , making the tool expensive to manufacture and cumbersome to manoeuvre.

Other types of running tools have a stab and hinge over mechanism in which the stab member is received by a guide funnel of a subsea structure. Moreover, the stab is pivotally mounted to the tool in a manner that allows the stab to pivot in a vertical plane when the tool is oriented in an upright direction . The hinge over mechanism provides particular advantages during the deployment of primary flowlines lowered from a surface vessel. A difficulty with tools having the hinge over mechanism is that the tool can be unstable causing the tool to orient itself at an angle to the vertical, making the insertion of the stab into a fixed vertical guide sleeve on the subsea structure problematic.

It is an object of the present invention to provide an alternative running tool and method that alleviates the problems of the devices currently in use .

SUMMARY OF THE INVENTION

Throughout this disclosure, the terms "subsea structure" and "subsea host structure" may be any subsea structure including, but is by no means limited to fixed and mobile sea structures such as manifolds, pipe line end terminations (PLETs) , well bore heads, pipe line end manifolds (PLEMs), subsea trees, submersible structures, semi-submersible structures, wharfs and any other structure below the surface of the sea .

According to the present invention there is provided a running tool for locating a free connector hub of a flowline onto a fixed hub that has been pre-instailed onto a subsea host structure, the running tool including: a coupling assembly for connecting with a cooperating coupling assembly of the subsea structure and the couplings are adapted so that when interconnected, the tool can move about an upright or substantially upright pivot axis that is defined by the coupling assemblies; an arm assembly connected to the coupling assembly of the running tool that releasably carries the free hub to be installed; a registration device that is operative to prevent pivotal movement about the upright or substantially upright axis when the free hub, being carried by the tool, is substantially aligned in registration above the fixed hub; and an elevator actuator that is operable, when located in the registration position, to move the free hub downwardly and seat the free hub onto the fixed hub.

One of the advantages of the present invention is that when the coupling assemblies are in the phase of being interconnected, the tool can be interconnected with the free hub located at an angular orientation about the upright pivot axis of the couplings . Moreover when connecting the tool, the tool is suspended on a tie-line that allows the tool to orient itself under gravity and prevailing forces such as, but by no means limited to, the stiffness of the flowline. By allowing the tool to be interconnected in which the free hub is at an angular orientation about the upright pivot axis, deflection of the flowline is minimised which in turn reduces possible destabilisation forces on the tool during interconnection.

Another advantage of the present invention is that once the free hub has been brought into centralised aligned position after interconnection, further pivotal movement of the tool can be prevented.

The coupling assemblies of the tool and the subsea structure may be in the form of a male piece such as a stab, or a female piece, preferably in the form of a tubular sleeve and suitably in the form a tubular guide funnel having walls that taper, at least partly along the length of the funnel , from top to bottom .

Suitably, the coupling assembly of the tool is a stab and the coupling assembly of the subsea structure is a guide funnel . The upright pivot axis of the tool is suitably defined by pivotal movement of the tool when the stab is completely or partially received by the guide funnel .

Suitably, the registration device is operative when the male piece of the coupling assembly is completely or substantially completely received by the female tubular sleeve.

Throughout the procedure in which the tool is coupled to the subsea structure, a tie-line attached to the tool is controlled from a vessel at the sea surface. The tie-line may be fastened to one or more than one point on the tool, and ideally at a series of points to position the tool in an orientation that facilitate engagement of the couplings . This is achieved when the stab is oriented downwardly and suitably approximately vertical downwardly and correspondingly, the guide funnel is oriented upwardly and suitably vertically upwardly.

Preferably, the arm is pivotally connected to the coupling assembly of the tool about an axis, which when . the tool is oriented upright, is oriented horizontally or substantially horizontally so that the arm can be pivoted about the axis in an upward and downward direction. For example, the pivotal connection between coupling assembly and the hub is provided at a shoulder between the coupling, suitably in the form of a stab and the arm.

When in use, a tie line is connected to the arm and the stab is free to point downwardly under gravity, thereby facilitating the stab being lowered into the guide funnel .

It is also conventional for additional tie lines and slings to be attached to the flowline at a distance from the tool. The additional tie lines and slings may also need to be released to lower the coupling assembly, suitably a stab, of the tool onto the coupling assembly of the subsea structure, suitably a guide funnel. Once the coupling assemblies of the tool and subsea structure are connected, the support lines can be manoeuvred to pivot and shift the free hub about i) the horizontal pivot axis between the stab and the arm, and ii) to pivot the tool about the upright pivot axis of the coupling assemblies. In the event that the free hub can not be located in the registration position by manoeuvring the tie line and slings alone, additional actuators, suitably hydraulic actuators can be fitted between the tool and the subsea structure by the ROV to pull the free hub downwardly and/or about the pivotal axis of the coupling assemblies into a registration position.

Suitably, the registration device includes a male formation that is operatively engaged by the female formation .

Suitably, the female formation of the registration device includes an opening such as slot or cutout that receives the male formation such as a cooperating key that is received by the female formation .

Suitably, the male formation of the registration device is constrained to prevent rotational or lateral movement relative to the pivot axis of the coupling assembly of the tool so that once the male formation is operatively received by the female formation, the coupling assembly is prevented from rotating.

Suitably, the female formation is a slot in the upper face of the guide funnel that receives the key. Specifically the key is received by the slot when the free hub being carried by the tool is located in registration above the fixed hub.

Suitably, the arm is pivoted fully downwardly before pivoting the tool so as to position the free hub into registration with the fixed hub. When this is achieved, suitably the axis of the free hub is substantially aligned with the axis of the fixed hub.

When the axes of the free hub and fixed hub are substantially aligned, the elevator actuator is operable to move the free hub substantially along the axis of the pre-installed hub.

The elevator actuator may be in the form any actuator including screw, rack and pin and intermeshing gears. However, suitably the elevator actuator is in the form of one or more hydraulic piston and cylinder devices, and preferably a pair of the hydraulic devices . In an embodiment, the or each hydraulic device is configured such that the cylinder is mounted above the piston, thereby placing the piston in tension until the free hub is seated on the fixed hub.

Once the free hub and fixed hub have been seated together, the elevator actuator is also operative to press the free hub and fixed hub together. A suitable clamping device may then be fitted to the free hub and pre- installed hub to form a fluid tight seal . Typically an ROV is used to install the clamping device and, in addition, release the free hub from the tool.

Suitably, the elevator actuator includes a framework including a pair of parallel plates to which the hydraulic devices are connected and a yoke formation connected to an end of the arm opposite to the end of the arm connected to the coupling assembly.

In the situation in which the elevator actuator is in the form of a hydraulic device, suitably the cylinder of the hydraulic device is located above the framework when the tool is positioned in an upright orientation and, the piston extends below the framework.

The tool may also include a tie guide for guiding a tie line on which the tool is suspended during interconnection of the tool to the subsea structure. The tie guide suitably includes a closed loop formation through which the tie line passes . When the tool is viewed in a substantially upright position, suitably the closed loop formation defines an opening located at the highest point of the tool through which the tie line passes .

Even more suitably, when the tool is positioned in an upright orientation, the loop formation extends from a highest point of the tool to a point above the fixed above the free hub, and if the free hub includes a goose neck, suitably adjacent to the goose neck of the free hub.

In an embodiment, the tie line on which the tool is suspended passes through the opening and is releasably fastened, either directly or indirectly to the free hub and if the free hub includes a gooseneck, ideally to the gooseneck. When the free hub has been installed, the tie line attached to the tool is able to be released, typically by means of an ROV and a recovery line that was also attached to the tool during the lowering of the tool can be used to recover the tool to the surface .

According to the present invention there is provided a method of locating a free hub connector of a flowline to a fixed hub connector that has been pre- installed to a subsea host structure using a running tool, the method including the steps of: a) interconnecting the tool to the subsea structure, wherein the tool carries the free hub to be connected to the fixed hub and the free hub is joined to a flowline; b) allowing the tool to pivot about an upright pivotal axis formed at the interconnection between the tool and subsea structure in step a) , and allowing the free hub to move at least partially about the pivot axis over an arch extending side-to-side of the fixed hub so as to minimise deflection in the flowline adjoining the free hub; c) after steps a) and b) moving the free hub from an out-of-aligned position to a position in which the free hub is located in registration with respect to the fixed hub; d) preventing the tool from moving from the registration position; and e) moving the free hub downwardly toward the fixed hub and landing the free hub on the fixed hub.

It will be appreciated by those skilled in the art of the present invention that steps a) and b) may be carried out simultaneously, disjunctively or consecutively. Similarly, steps c) and d) may be carried out consecutively in any order, disjunctively or simultaneously .

Suitably, step a) includes interconnecting upwardly oriented male and female formations . For example, the tool includes a male elongate piece such as a pin or stab and the subsea structure includes a female tubular sleeve such as a guide funnel that is mounted in an upward orientation to the subsea structure. In this situation, step a) includes locating the stab of the tool in the guide funnel and lowering the tool until a downwardly facing surface of the coupling assembly lands on an upwardly facing rim of the guide funnel .

Step b) may include moving the free hub over a substantially horizontal plane.

Moving the flowline according to step c) may also includes moving the flowline in a side-to-side direction of the fixed hub or by lowering the flowline .

Step e) may include operating an elevator actuator which lowers the free hub toward the fixed hub. Step e) may also involve pivoting the free hub over an arch in an upward and downward direction . Moving the free hub in this manner can be achieved by manoeuvring the flowline by the tie lines.

The method may also include step f) which involves installing a clamping device to the free hub and the pre-installed hubs seated together during step d) . Suitably, installing the clamping device forms a fluid tight seal between the free hub and pre-installed hub.

Once the clamping device has been installed, the method may also include releasing the free hub from the tool, and enabling the tool to be retrieved.

According to the present invention there is provided a running tool for locating the free hub of a connector hub of a flowline to a fixed pre-installed connector hub mounted to a subsea host structure, the tool including: a) an coupling assembly that couples the tool to the subsea structure such that the tool can pivot or rotate about an upright or substantially upright pivot axis of the coupling; b) a support assembly connected to the coupling assembly, the coupling assembly carrying the free connector hub to be installed; c) a locking device that is operative to prevent pivotal movement about the upright or substantially upright axis of the couplings when the free connector hub registers over the fixed pre-installed connector hub; and d) an elevator actuator for raising and lowering the free connector hub into engagement with the fixed pre- installed connector hub.

BRIEF DESCRIPTION OF THE FIGURES

An embodiment of the present invention will now be described in detail with reference to the accompanying figures , of which :

Figures 1 and 2 are front and back perspective views of a running tool carrying a free connector hub to be connected to a fixed pre-installed connector hub mounted on a subsea structure ;

Figures 3 and 4 are front and back perspective views of a tie-in porch that is typically mounted to a subsea structure such as a tree, the tie-in porch including the pre-installed fixed hub and a guide funnel;

Figure 5 is an perspective view of the back of the running tool and the tie-in porch shown in Figures 1 to 4, wherein the running tool has been coupled to the tie-in porch and with a registration and locking device of the tool disengaged;

Figure 5A is a close up view of the alignment registration and locking device as shown in Figure 5 ;

Figure 6 is perspective view of the back of the running tool and the tie-in porch shown in Figures 1 to 4 , wherein the running tool has been coupled to the tie-in porch and with the registration and locking device engaged;

Figure 6A is a close up view of the registration and locking device as shown in Figure 6; Figures 7 to 11 illustrate a sequence of steps for deploying a tool carrying a free hub in an orientation in which the free hub being stalled is located in an initial course alignment with the fixed hub, and in particular, Figure 7 illustrates an approach phase in which the tool shown in Figures 1 and 2 approaches the tie-in porch shown in Figures 3 and 4 mounted to subsea structure;

Figure 8 illustrates an orientation phase in which the stab of the tool is located above the guide funnel of the tie-in porch; Figure 9 illustrates a stabbing phase in which the stab of the running tool is lowered into the guide funnel ;

Figure 10 illustrates a landing phase in which the stab of the running tool is fully received by the running tool and the running tool is in the process of the being hinged over;

Figure 11 illustrates an alignment phase in which the tool is pivoted about an upright axis of the stab and guide funnel so as to place the free and fixed hubs in registration ;

Figure 12 is an overhead view of the running shown in Figure 11 in which the tool is pivoted between an offset positions as shown in dashed lines and a centralised position as shown in solid lines ;

Figures 13 to 17 illustrate a further sequence of steps involving connecting the free hub and fixed hub, and in particular Figure 13 illustrates a preparation connection phase in which the flow line, once aligned with the desired corrode, is lowered to the seabed;

Figure 14 illustrates a connection phase involving lowering of the free hub into the fixed hub via an elevator actuator and attachment of a clamp to form a fluid tight connection;

Figure 15 illustrates a disengagement phase in which the tie line is disengaged and the elevator actuator retracted into a raised position;

Figure 16 illustrate a tool recovery phase involving reconnection of the tie line to the tool to a tie line guide ; and

Figure 17 illustrates the next step of the tool recovery phase in which the tool is lifted clear of the tie-in porch and raised to the surface .

DETAILED DESCRIPTION

The present invention will now be described in detail with reference to the embodiment of a running tool 20 shown in the Figures.

It will be appreciated that the running tool 20 can be used for locating a free connector hub 21 of any size to a pre-installed fixed connector hub 22. By way of example, the running tool shown in the figures may be capable of carrying and locating connector hubs having bore sizes in a range of 1 to 4 inches. However, it is within the scope of the present invention that modifications may be made to the embodiment shown in the figures so that the running tool can be used for carrying and locating free connector hubs of larger sizes, for example, free hubs 21 having bore sizes of 5 or 6 inches.

Figures 1 and 2 illustrate front and back perspective views the running tool 20 in which the tool 20 is located in an upward orientation which is an ideal position for interconnecting the running tool 20 to a subsea host structure 23. The running tool 20 comprises a coupling assembly having a stab member or pin 24 having a circular cross section and a shoulder 25 at the upper end of the stab 24 that is pivotally mounted to an arm 26 about a substantially horizontal axis, and an elevator actuator 27 connected to the arm 26 by a set of parallel plates 28 and a yoke formation 29 at an end of the arm 26 opposite to the end at which the arm 26 is pivotally mounted to the shoulder 25. Mounted to the lower end of the elevator actuator is the free hub 21 that is releasably carried by the tool 20 for connection to a fixed hub 22 that has been pre-installed to a sub-sea structure 23. The free hub 21 having a vertically bore when the tool is oriented upright and a conventional goose neck 30 arrangement having an end fitting that, although note shown in the Figures 1 and 2, is connected to a flow line.

Figures 3 and 4 illustrate front and back perspective views of a tie-in porch that is typically mounted to a subsea structures such as a tree (not shown) . The tie-in porch comprises a platform 31 above which the pre-installed fixed hub 22 faces upwardly therefrom, and a lower bend spool 32 that extends below the platform 31 and rearwardly. A coupling formation in the form of a guide funnel 33 for receiving the stab 24 of the running tool 20 is rearwardly offset from the fixed hub 22 and extends upwardly from the platform 31. The diameter of the guide funnel 33 enables the stab 24 to be lowered into the guide funnel 33 while the running tool is suspended on the tie line (see figures 7 to 11) . Importantly, an upper opening 34 of the guide funnel 33 includes a notch or a cut-out 35 for receiving a cooperating keyed or male formation 36 extending downwardly from an abutment plate 37 at lower edge of the shoulder 25 of the tool 20. The key 36 and cut out 35 are located such that the key 36 is aligned and received by the cut out 35 when the abutment plate 37 rests against the upper opening 35 of the guide funnel 33 and the free hub 21 is aligned in registration above the pre-installed hub 22. Figure 5 illustrates the situation in which the free hub 21 is located in registration with the fixed hub 22 and for the purposes of clearly identifying the components of tool 20, the abutment plate 37 is shown as spaced upwardly from the opening 34 of the guide funnel 33. Figure 5A is an enlarged view of the key 36 and cut out 35 formations.

Figures 6 and 6A are the same views those shown in Figures 5 and 5A, save for the stab 24 being shown in a fully lowered position with the abutment plate 37 engaging the upper opening of the guide funnel 34 and the key 36 being located in the cut out 35.

When in use, the stab 24 is initially received by a guide funnel 33 mounted to the subsea structure and the running tool 20 is allowed to pivot about a substantially vertical axis defined by movement of the stab 24 within the guide funnel 33 during the process of lowering the stab 24 down the guide funnel 33. An advantage provided by this procedure is that deflection of the flowline is minimised by allowing the tool 20 to pivot about an upright axis. Once the stab 24 has been substantially fully received by the guide funnel 33, and the downwardly facing abutment plate 37 at the upper end of the stab 24 contacts the opening 34 of the guide funnel 33, the tool 20 can be pivoted until the free hub 21 registers above the fixed hub 22 in which the vertical axis of the free and fixed hubs 21 and 22 are substantially aligned.

The elevator actuator 27 is in the form of a pair of hydraulic piston and cylinder assemblies that are connected to the arm 26 via a pair of the parallel plates 28 connected to a yoke 29 at the end of the arm 26. The hydraulic assemblies are contained within an external cylindrical housing.

The hydraulic assemblies are located in an up position in Figures 1, 2, and 5 to 11.

A tie line guide 38 for guiding a tie line attached to the free hub 21 is mounted to the upper portion of the tool 20. The tie line guide 38 includes an upwardly extending portion 39 and horizontally extending portion 40, whereby both portions 39 and 40, define a continuous opening through along which the tie line can passes. We have found that the best configuration of the tie guide 38 is when a portion of the opening extends above and forwardly of the elevator actuator 27. When in use, a tie line can then be attached to the running tool 20 by connection to an upper face of the gooseneck 30 that passes through the opening of the tie guide 38. The tie guide 38 is configured to assist in positioning the running tool 20 in an upward orientation as shown in figures 7 and 8.

Figure 7 illustrates an approach phase in which the running tool 20 is suspended from a tie line 42 connected to the gooseneck 30. A remotely operated vehicle (ROV) having onboard lighting and camera facilities transmit pictures of the guide funnel 33 of the subsea structure 41 and the stab 24 formation to operators of the tie line 42 on board a vessel at the surface of the sea . Figure 8 illustrates the next orientation phase which involves manoeuvring the tie line 42 of the running tool 20 and a primary lifting sling (not shown) that is attached to the flowline 43 at a point of approximately 10 metres from the running tool 20 such that the tool 20 is moved into an upright orientation in which the stab 24 points downward and suitably vertically downward.

Figure 9 illustrates a stabbing phase in which the operator releases additional tie line 42 so that the stab 24 slides down inside the guide funnel 33 until the abutment plate 37 rests against the upper opening 34 of the guide funnel 33.

Figure 10 illustrates the abutment plate 37 resting against the upper opening 34 of the guide funnel 33 and the stab 24 extending downwardly in the guide funnel 33. From the position shown in Figure 10, the flowline 43 is then manoeuvred, in particular, by lowering the lifting sling so that the arm 26 carrying the free hub 21 pivots downwardly about the pivot connection at the shoulder 25 of the stab 24 until the free hub 21 is oriented substantially vertically as shown in Figure 11. If necessary, an actuator, for example an actuator installed by the ROV between the arm 26 and the subsea structure can be used to pivot the arm 26 about the horizontal pivot axis toward the subsea structure until a buffer 44 contacts the subsea structure 41, and suitably the guide funnel 33.

In addition, the lifting sling can be moved so as to pull the flowline 43 from side-to-side and in turn, pivot the tool 20 about the upright or substantially upright pivot axis of the stab 24 and guide funnel 33. Figure 12 illustrates an overhead of the tool 20 in which the pivotal movement of the tool 20 and movement of the flowline 43 from side-to-side is shown by the flowline 43 in broken lines . The flowline 43 shown in solid lines represents the flowline 43 located in the flowline 43 corrode and the free hub 21 located centrally above and in registration with the fixed hub 22.

Throughout the alignment phase shown in Figures 11 and 12, the abutment plate 37 of the shoulder 25 of the stab 24 is seated on the upper opening 34 of the guide funnel 33. For the purposes of clarity, Figures 5 and 5A illustrate the abutment plate 37 spaced above the upper opening 34 of the funnel 33. The key formation 36 extends downwardly from the abutment plate 37. The key 36 and slot 35 are located so that as the tool pivots about the upright or substantially upright axis of the guide funnel 33, the key 36 is received by the slot 35 when the free hub 21 is located in a centralised position above the fixed hub 22 shown in Figures 6 and 6A. When located in the centralised position, the axes of the free and the fixed hubs 21 and 22 are substantially aligned in registration.

The lifting sling controlling the flowline 43 may then be used to lower the flowline 43 onto the seabed as shown in Figure 13. If present, protective caps are also removed from the free and fixed hub by means of the ROV.

The elevator actuator 27 may then be operated to lower the free hub 21 downwardly onto the fixed hub 22 to locate the hubs 21 and 22 into mating relationship as shown in Figure 14. The ROV is then manoeuvred into position to install a conventional three piece clamp such as a CVC™ or Optima™ clamp to form a fluid tight seal between the mating hubs .

Figure 15 illustrates a disengagement phase in which the tie line 42 is release from the gooseneck 30 of the now installed free hub 21 , and the elevator 22 disconnected from the free hub 21. Once disconnected, the elevator 27 is retracted back into in raised position to clear the connection and complete the installation procedure .

The running tool 20 is then retrieved for future use firstly by connecting the tie line 42 to the tool 20, for example, by connecting the tie line 42 to the tie line guide 38 with the assistance of the ROV as shown in Figure 16. The running tool 20 is then lifted clear of the subsea structure 41 by withdrawing the stab 24 from the guide funnel 33 and recovered to the surface vessel .

One of the benefits of the embodiment described above is that during lowering of the running tool, deflection in the flowline is minimised by allowing the free hub to move in an arch extending side-to-side of the fixed hub during interconnection of the running tool to the subsea structure . This allows an optimal orientation of the stab to be achieved while lowering the running tool and also minimised stresses on the running tool.

Another advantage of the embodiment described above is that the running tool and guide funnel can be made from lower gauge material compared to other running tools. For example, a running tool according to the preferred embodiment weighing in the range of 800 to 1200 kilograms can be used for installing free hubs having a bore in the range of 1 to 4 inches. In comparison, other running tools currently available can weigh as much as up to 5000 kilograms for installing the same size free hubs . This provides savings in manufacturing costs and also enables easier handling of the tool particularly on the deck of the vessel and when lowering and retrieving the tool . Furthermore , in the event that control over movement of the running tool is temporarily or permanently lost during use, the running tool is less likely to cause structural damage to surrounding equipment such as subsea structures on the count that the running tool itself is lighter than other running tools currently available.

Those skilled in the art of the present invention will appreciate that many modifications and variations may be made to the embodiment of the invention depicted in the drawings without departing from the spirit and scope of the present invention .