Pipeline propulsor - an improved method for interrupted reeled pipe lay of mechanically lined pipe for planned or unplanned reasons

Abstract

Method of reel laying Mechanically Lined Pipe, conducted with an internal hydrostatic pressure of the 30-50 bar or greater without interruption of this hydrostatic pressure enabling the reel lay pipe to be safely back reeled under pressure at any stage, without risk of wrinkling and eliminating introduction of unwanted air pockets into the reel laid pipe. It enables In Line Structures to be incorporated into the pipe lay string and obviates the requirement to reflood and re-pressurize the riser string. It enables rapid lay down of the pipeline being laid without unpressurised back-reeling, in the event of deteriorating weather. The key element of apparatus in this improved method is a pipeline propulsor coupled to an insolation plug and a robotic positioner as a plug train whereby the plug train is moved for maintaining its position between the reel storage drum and the reel aligner straightener during laying.

Description

[0001] PIPELINE PROPULSOR - AN IMPROVED METHOD FOR INTERRUPTED REELED PIPE LAY OF MECHANICALLY LINED PIPE FOR PLANNED OR UNPLANNED REASONS.

[0002] The present invention relates to a pipeline propulsor tool which allows a user to propel a multi set pipeline isolation tool through a pressurised or unpressurised dead headed pipeline to a chosen location, in order to create a high pressure internal stop in the pipeline thus allowing a user to maintain a high pressure area within a specific section of pipeline.

[0003] Background to the Invention

[0004] The following documents are part of the prior art of this invention.

[0005] WO 2008 / 072970A1 Statoil - Endal - 5-25 bar method

[0006] WO 2011 / 051218A1 Subsea 7 - Mair - Reeling on process

[0007] WO 2011 / 124919A1 Subsea 7 - Mair - Wrinkle height radial gap

[0008] WO 2011 / 051221 A1 Subsea 7 - Mair - with an End cap

[0009] WO 2010 / 010390A1 Technip - Howard - Spooling bi-metallic pipelines

[0010] WO 2018 / 051191A1 Technip - Chalmers - Cut + ILS installing vent hose

[0011] US 2022 / 0042624A1 Subsea 7 - Neto - Joining ILS Air removal

[0012] WO 2003 / 0056954A1 Carsphairn - Early - Crawler plug

[0013] WO 2005 / 0241710A1 Carsphairn - Early - Autonomous plug

[0014] WO 2014 / 0013737A1 SPC - Early - Miniaturized Autonomous plug

[0015] WO 2014 / 0020593A1 SPC - Early - Plug Positioner

[0016] MLP (Mechanically Lined Pipe) is a sleeve of corrosion resistant alloy such as 316 stainless installed within the lumen of a carbon steel carrier pipe. MLP is used to reduce cost of bringing corrosive hydrocarbons up to an FPSO (Floating Production Storage Offshore) vessel. During Reel Pipe Lay, the weaker thin MLP liner can dis-bond from the thicker stronger carbon steel carrier pipe at the intrados when going over the Aligner and cause wrinkling of the liner.

[0017] Liner wrinkling can be prevented by applying an internal hydrostatic pressure of 30-50 bar or greater throughout the entire reel lay process, i.e in the range of approximately 30-120 bar. At planned stages in the reel lay program, In Line Structures (PLETs, ILTs, PLEMs etc) may be incorporated into the line being laid, or at unplanned stages in the reel lay program (such as deteriorating weather) the reel lay operation may have to be suspended and the pipe laid down on the sea-bed, to reduce top tension and free the vessel to seek shelter. In all such cases the pipe being laid must be cut and the hydrostatic head and its constituent fluid is lost and air pockets are introduced. On such occasions (when an intermediate section is not cut out) the pipe must be back reeled without internal hydrostatic pressure, and wrinkling can occur.

[0018] Transportation of hydrocarbons through pipelines is a well-known activity within the subsea industry. Pipelines are laid along the seabed in order to connect oil and gas fields to storage or processing facilities such as onshore processing plants, floating production storage and offloading (FPSO) installations or offshore platforms. Hydrocarbons may be corrosive in nature and thus measures are taken to protect the inside of carbon steel pipelines from corrosion failure.

[0019] Pipelines formed of corrosion resistant alloys such as 316 stainless, Incalloy or Titanium can be used, but these are more expensive options. Alternative measures to mitigate the corrosive effects of hydrocarbon transport include installing thin liners, for example 3mm thick, inside the pipelines which are more resistant to the corrosive properties of the hydrocarbons. A typical example of such a liner would be a corrosion resistant alloy (CRA), such as for example 316 Stainless steel. These liners are connected to the inside of the carbon steel carrier pipeline through a variety of processes including metallurgical bonding or mechanical lining.

[0020] Such pipelines may also be installed using a variety of methods including reel lay as disclosed in WO 2008 / 072970A, and W02011 / 051218A where pipe joints are welded into pipeline stalks in a spool-base and then spooled onto a large drum which is located on a reel lay vessel which is docked at the spool-base. Reel lay operations involve several stress cycles for the pipeline as the pipeline is bent in order to be reeled onto the reel lay vessel drum at the spool-base and then the pipe is reverse bent, during the laying operation offshore, typically over a reel aligner, in order to straighten the pipe out again before it is lowered down and installed at its final destination on the seabed. It is known in the art and disclosed in WO 2010010390A and WO2011 / 048430A that reeling of mechanically lined pipes can cause wrinkling, which is a type of localised buckling of the inner pipe’s corrosion resistant alloy liner material. In particular, when the pipeline undergoes bending cycles during the reeling process. Wrinkling of the inner liner is not acceptable as such buckling of the liner can cause flow and pigging problem and prevents the pipe from meeting its agreed contracted installation requirements.

[0021] In order to eliminate wrinkling of mechanically lined pipe during the reel lay process, the inside of the mechanically lined pipeline is pressurised, to an internal hydrostatic pressure of 30 bar or more. Using this method, no wrinkles are formed on the intrados when moving the pipe over a rounded surface as the internal pressure exerts a compressive force on the liner which must be overcome for a wrinkle to form. However, installing a pressurised pipeline presents further technical challenges and increased risk to personnel and equipment. As wrinkling only occurs at certain stages of the reeling process, namely the bending cycles, it is not necessary to always maintain pressure throughout the full pipeline being reel laid, it is only necessary to maintain pressure on the topside section of pipeline which is undergoing the activity which leads to wrinkling formation, i.e. , the bending and straightening processes.

[0022] In addition, there are instances when the pipeline must be reverse reeled on the reel aligner straightener or the pipe storage drum, or both. In these instances, typically the pressure cannot be maintained in the pipeline as a whole and if the pipe needs to be reeled over a curved surface unpressurised, it is then subject to a bending cycle which poses the risk of wrinkle formation of the inner liner. These instances may not be related to the actual mechanically lined pipe per se but to the laid pipeline structure, such as for example when the laid section of pipeline is hung off, de pressurised, cut off and re-terminated. In these instances, the remaining reel of pipe must be moved upwards (in the direction of the reel aligner straightener) in order to provide space for the operator at the cut point of the pipe so that a new lay down head or pipeline end termination (PLET) or pipeline end manifold (PLEM) structure can be welded in place as disclosed in GB2553837 and WO2018 / 051191. Upward movement (also known as reverse reeling) of the unpressurised pipe poses the risk of inner liner buckling. If wrinkles are formed at this stage, the wrinkled joint must be cut out of the pipeline which is a process that requires vessel time and poses a heightened risk of damage to equipment and handling risk to personnel, in addition to cost of the wastage of the joint of mechanically lined pipe itself. Prior art documents US9400001 W02005 / 0241710 and WO2014 / 0013737 disclose hydraulic systems for high-pressure autonomous pipeline isolation tools used in pipeline isolation and in autonomous multiset pipeline isolation. They are moveable high pressure isolation valves which functions inside a pipeline.

[0023] Prior art documents US8950338 and WO2014 / 0020593 disclose a robotic pipeline tool suitable for pushing or pulling other pipeline tools, such as an autonomous isolation plug, within a pipeline. The robotic pipeline tool comprises a first part and a second part which are hydraulically separable and a plurality of hydraulically operable pipeline engaging means for hydraulically gripping with the interior surface of the pipeline such that the tool is moveable within a pipeline. It is a robotic movement system which positions pipeline tools inside pipelines without any requirement to use any propelling pigging medium (treated water, MEG etc.).

[0024] It will be appreciated by those in the industry that the existing prior art arrangements do not facilitate effective movement and long-distance location within the pipeline, in so far as an effective autonomous thruster or propulsor motive mechanism which is capable of tracking and positioning the autonomous pipeline isolation tool has not been provided for in these existing systems.

[0025] It is to be appreciated that there is a need in the industry for a device which allows an autonomous pipeline isolation tool to be propelled through a reel lay pipeline which is capable of optimally positioning the autonomous pipeline isolation tool for the maintenance of a section of pipeline at a predetermined internal pressure.

[0026] It is a therefore an object of the present invention to provide a pipeline propulsor which enables the existing technologies of US9400001 and US8950338, contained within a Plug Train to be moved long distances, and then to be accurately positioned within a reel laid pipeline, to maintain the 30 bar or greater internal pressure, in all pipe movement over rounded surface operations. It is also an object of the invention to provide effective high- pressure isolation of the Reel Lay pipe string, to enable 30 to 50 bar (or higher) pressure to be maintained on the drum end of the product, so that the product can be back reeled without incurring wrinkles. As the pipe is wholly water filled, relatively small changes in volume can lead to significant changes in pressure, therefore it is also an object of the invention to eliminate the drain down of fluid from the vertical riser section of the Reel Lay pipe, below the Reel Aligner Straightener and thereby prevent air pockets developing.

[0027] Summary of the Invention

[0028] The present invention is a device which allows a pipeline isolation train consisting of coupled units of US9400001 WO2014 / 0013737 and US8950338 WO2014 / 0020593 to be autonomously propelled through a reel laid pipeline in terms of which the device is capable of optimally positioning the pipeline isolation train for the maintenance of a section of pipeline at an internal pressure of 30 bar or greater, throughout multiple cycles of the reel lay process.

[0029] This pipeline propulsor is coupled to the pipeline isolation train and includes a driving or propulsion mechanism as well as autonomous tracking and positioning capabilities.

[0030] In accordance with an embodiment of the invention, there is provided a pipeline propulsor including: an enclosed multi-rotor system operable to move the propulsor within the pipeline, and a fluid-cooled propulsion motor, operable to drive the enclosed rotor system; wherein said pipeline propulsor is operable to facilitate effective, autonomous movement of one or more wheeled pipeline movement and isolation tools attached to the propulsor, within a train configuration.

[0031] In this embodiment of the invention, said pipeline propulsor is operable to facilitate autonomous movement of the isolation plug train within the pipeline, to create an internal stop in the pipeline at times required and maintain a predetermined pressure level over a designated section of the pipeline. In this manner, the pipeline propulsor is operable to assist in eliminating wrinkling in mechanically lined pipe during reel lay operations.

[0032] In an embodiment, the fluid-cooled propulsion system is implemented as a fluid- cooled electric motor. In an alternative embodiment, the enclosed rotor system takes the form of an enclosed impeller, mounted perpendicular to the pipeline axis. Additionally, the axis of the impeller is rotated to a 90-degree angle to the longitudinal axis of the pipeline, preventing torque-induced turning of the train configuration during operation.

[0033] In a further alternative embodiment, the fluid-cooled propulsion system is realized as a fluid-cooled jet propulsion system. This system includes components such as an inlet, a duct, a shaft, a propeller, one or more stators, an intake nozzle, and an outflow nozzle outlet. Notably, the inlet is positioned within the pipeline fluid to minimize hydraulic losses, and it exhibits circular symmetry to reduce constriction losses. The constant inlet geometry is intended to mitigate outlet vortex issues, and the shaft is configured to offer minimal resistance to incoming inlet fluid. In a preferred embodiment, the propeller is meticulously designed to minimize the marginal tip distance of the propeller gap, thereby reducing tip leakage vortex-induced pressure changes.

[0034] In another embodiment, the enclosed rotor system adopts the form of a ducted propellor unit, strategically positioned at the forward end of the propulsor. Specifically, in a preferred configuration, the ducted propellor unit is located at an operatively fore end of the horizontal train configuration, in the catenary between the pipe storage drum and the reel aligner straightener. Consequently, the ducted propellor unit operates in a pulling configuration. The pipeline propulsor, in all embodiments, incorporates multiple spring-loaded wheels designed to maintain the propulsor configuration axially central and to prevent undesired rotation.

[0035] In an embodiment, the one or more pipeline tools in the train configuration include one or more of the following: a double block and bleed multi-set wheeled autonomous pipeline isolation tool, and a wheeled robotic walking tool, operable to move the isolation tool up a riser and over the reel aligner straightener, into a relatively horizontally positioned section of the pipeline, in use.

[0036] In an embodiment, the pipeline propulsor includes a dependable power source. In a preferred embodiment, the power source is provided in the form of a suitable battery, said battery being selected to meet the specific energy demands of the pipeline propulsor^

[0037] In an embodiment, the pipeline propulsor includes a control means operable to manage the operation of the propulsor, in use. In this embodiment, the control means includes an electronic speed controller and / or a power switch, operable to provide flexibility in controlling the pipeline propulsor’s movement within the pipeline, in use.

[0038] In an embodiment of the invention, the pipeline propulsor may include one or more universal ball joints coupled at a preferred distance from an operatively rear end of the isolation train configuration. In an alternative embodiment, the one or more ball joints are coupled at a preferred distance from an operatively fore end of the isolation train configuration. In this embodiment, the preferred distance is determined by calculation and verified by assembly and integration.

[0039] In an embodiment of the invention, the pipeline propulsor is sized in relation to the inner diameter of the pipeline to ensure efficiency of the propulsor in relation to such considerations as viscous drag, and the passage of fluid around the propulsor. In this embodiment, the ratio of pipeline ID in respect of the size of the propulsor power pod in relation to the size of the pipeline, has been determined as efficient for the pipeline tools to navigate through the static fluid deadheaded within the pipeline.

[0040] In an embodiment of the invention, the pipeline propulsor is designed to effect the necessary thrust to enable it to propel the isolation train efficiently within the pipeline.

[0041] In an embodiment of the invention, said pipeline propulsor includes an autonomous tracking and positioning system, operable to facilitate Propulsor to maintain autonomous movement. In this embodiment, the tracking and positioning system is operable to ensure that the pipeline propulsor maintains its dynamic lock position within the desired location in the pipeline generally the near horizontal catenary between reel aligner straightener and pipe storage drum. In an embodiment, the autonomous tracking and positioning system are integrated, ensuring that the one or more pipeline tools mechanically coupled to Propulsor maintain their position within the desired location in the pipeline.

[0042] In this embodiment of the invention, said autonomous tracking and positioning system include various options, each of the one or more options being operable to maintain the isolation train configuration at a specific horizontal position within the pipeline. In this embodiment, each of the one or more options depend on an outside reference or null point inside the pipeline for the train configuration to home onto, dynamically lock onto or reference against. In an embodiment of the invention, a first option for an autonomous tracking and positioning system is contemplated, involving the utilization of two isotopes. Within this embodiment, the pipeline propulsor is equipped with a first isotope positioned inside the train configuration in the pipeline. Concurrently, a second isotope is situated outside the pipeline. Illustratively, the first isotope may be Cs 137 with a 30-year half-life. Correspondingly, the second isotope could be Tantalum 182 with a distinctly different keV signature. Significantly, the isotope within the train configuration eliminates the necessity for a battery, facilitating the determination of the train configuration's location. The embodiment further incorporates at least two scintillating detectors located inside the pipeline on the train configuration, supplying positional reference data on the external isotope. This configuration enables the train configuration to autonomously establish and maintain its preferred position within the pipeline, for that required period of the mission.

[0043] In this embodiment of the invention, a second option for an autonomous tracking and positioning system is contemplated, featuring the deployment of an Extremely Low Frequency (ELF) pinger. The pipeline propulsor within this embodiment is equipped with a robust high-powered ELF pinger positioned outside the pipeline. Additionally, a positioner control pod containing precisely fixed onboard ELF receivers is located inside the pipeline, holding position data on the null point of the external pinger. It is noteworthy that, in an alternative embodiment, the pipeline propulsor may include a second magnetic pinger operating on a different frequency, also positioned inside the train configuration. This alternative arrangement serves to define the location of the isolation train configuration within the pipeline horizontal catenary during operation.

[0044] In this embodiment of the invention, a third option for an autonomous tracking and positioning system is contemplated, involving the use of an acoustic pinger. Within this configuration, the pipeline propulsor is furnished with an acoustic receiver positioned inside the train configuration. This receiver is operable to track an acoustic pinger located outside the pipeline, facilitating autonomous tracking and positioning of the train configuration within the pipeline.

[0045] In an embodiment of the invention, a fourth option for an autonomous tracking and positioning system is presented, involving the integration of one or more inclinometers. Within this embodiment, the pipeline propulsor is equipped with one or more horizontal and / or vertical inclinometers, effectively controlling the isolation train configuration's position autonomously. Notably, one or more horizontal inclinometers are situated inside a power pod on the isolation train configuration, ensuring the maintenance of its position in the relatively horizontal catenary between the reel alignment straightener and the pipeline storage drum. In the event of the isolation train configuration drifting backward towards the reel aligner straightener, the changing inclinometer angle would activate the propulsion system, moving the isolation train forward, to a preferred mid-point location within the horizontal catenary, relative to a beacon marker positioned for catenary operations.

[0046] In an alternative embodiment of the invention, a fifth option for an autonomous tracking and positioning system is contemplated, constituting an amalgamation of multiple preceding options. As an illustrative example, the pipeline propulsor may incorporate a magnetic pinger beacon positioned outside the pipeline, operable to track a null point positioned receiver inside the pipeline on the isolation train configuration. This embodiment further integrates a backup horizontal inclinometer within the train configuration. In this scenario, the null point or reference point of the magnetic pinger outside the pipeline can be tracked by the magnetic receiver within the pipeline on the train configuration. It is to be appreciated that, in case of a failure or loss of relatively horizontal orientation by the magnetic receiver, the changing inclinometer value (from horizontal towards vertical) would activate the thruster, propelling the train configuration operatively forward towards its predetermined preferred location within the relatively horizontal catenary.

[0047] In another embodiment, a sixth option for an autonomous tracking and positioning system is envisaged, incorporating an inertial navigation system (INS) mounted inside the propulsor. In this embodiment, the INS is provided in the example form of a switchable INS which is keyed to the axial centre of the riser, to be regarded as its start point. In this embodiment, the keyed INS has a predetermined, preferred offset horizontal distance between the reel aligner straightener and Pipe Storage drum. In this embodiment, a lay vector and a path of pipelay is pre-programmed into software of the propulsor, to enable the plug train to continuously maintain its preferred offset horizontal distance relative to the axial centre of the start point. In this embodiment, the path of pipelay and the lay vector are in harmony with the pipelay vessel’s movements. In an embodiment of the invention, the pipeline propulsor is operable to operate within a non-fluid pipeline system. In this embodiment, the propulsor may be provided in the form of a nitrogen-purged gas turbine propulsor.

[0048] In an embodiment, the pipeline propulsor is operable to enable effective autonomous movement of more than one of a variety of pipeline tools, within a deep-water reel lay pipe- laying system, or any other pipeline lay, pipeline installation system or pipeline transportation system offshore or onshore.

[0049] The invention is set out in the appended claims.

[0050] The skilled person will understand that where the same feature has been referenced in different aspects of the invention, this feature comprises the same parts and operates in the same way unless otherwise stated.

[0051] Brief of the

[0052] Embodiment of the present invention will now be described with reference to the accompanying drawings in which:

[0053] Figure 1 illustrates a diagrammatic view of a reeled pipelay operation in which an Isolation Train containing pipeline propulsor is used., in accordance with an embodiment of the invention;

[0054] Figure 2A illustrates a side view of a reeled pipe lay operation.

[0055] Figure 2B illustrates component parts of the Isolation Train in which Propulsor is configured, located in the relatively horizontal catenary between the Reel Aligner Straightener and the Pipe Storage Drum.

[0056] Figure 3 illustrates the three constituent parts of the Isolation Train arrangement - Propulsor, Plug and Positioner.

[0057] Figure 4A illustrates a side elevation of Propulsor. Figure 4B illustrates a perspective General Arrangement view of Propulsor with its Control Pod.

[0058] Figure 4C illustrates a top view of one type of Propulsor mechanisms.

[0059] Figure 4D illustrates a perspective view of one type of the Propulsor mechanisms.

[0060] Figure 4E illustrates Propulsor within its wheeled centralising system.

[0061] Figure 5 illustrates a side elevation view of a Plug.

[0062] Figure 6A illustrates a side elevation view of Positioner retracted.

[0063] Figure 6B illustrates a side elevation view of Positioner extended.

[0064] Figure 7A illustrates a side elevation view of a Reel Lay Vessel moored up stern to a Spool

[0065] Base with its Lay T ower tilted at 45 degrees preparing to reel on water filled and pressurized Mechanically Lined Pipe.

[0066] Figure 7B illustrates a side elevation of the Reel Lay vessel outlining its key pipe reeling components.

[0067] Figure 7C illustrates additional key components of a Reel Lay vessel notably its cleaning, gauging and water filling pig - start point at the leading end of the pipeline.

[0068] Figure 7D illustrates the cleaning, gauging and flooding pig arrival at the last joint of pipe prior to reeling on.

[0069] Figure 7E illustrates the movement of the cleaning, gauging and flooring pig into the pig launcher receiver.

[0070] Figure 7F illustrates the installation of the Isolation Train into the pig launcher receiver.

[0071] Figure 7G illustrates that the Isolation Train has robotically walked into the last joint of pipe and the Plug has set. Figure 7H illustrates that the Pig Launcher Receiver and short spool has been cut off the end of the pipeline and moved away from the pipeline.

[0072] Figure 7I illustrates that an initiation head has been welded onto the trailing end of the pipeline.

[0073] Figure 7J illustrates that the plug within the Isolation Train has been unset, and that the Isolation Train has been propulsed to a preferred position 100m from the trailing end, and its hand brake pads have been engaged.

[0074] Figure 7K illustrates that the pipe containing the hand braked Isolation Train is pressurized and is being reeled onto the Pipe Lay Vessel.

[0075] Figure 7L illustrates that the Isolation Train has been reeled to it’s preferred operational location - midpoint in the relatively horizontal catenary.

[0076] Figure 8A illustrates Lay Tower has been rotated back to the vertical and the Initiation Head in the trailing end of the pipeline is connected to the Initiation wire which is connected to the seabed foundation / startup anchor.

[0077] Figure 8B illustrates a side elevation indicating the preferred horizontal location of the Isolation Train throughout pipeline Reel Laying operations.

[0078] Figure 8C illustrates configuration of the Isolation Train within the nearly horizontal catenary location where the hand brake pads are engaged in the final 80 metres of the pipe lay sequence.

[0079] Figure 8D illustrates the arrival of the Isolation Train in the vertical adjacent to the lower work station.

[0080] Figure 8E illustrates the locking of the Hold Off / Hang Off clamp.

[0081] Figure 8F illustrates the setting of the Plug within the vertical riser section of the pressurized pipeline. Figure 8G illustrates the hot tap and vent activity.

[0082] Figure 8H illustrates the cutting of the pipe below the set plug, which is keeping the pipeline back to the pipe storage drum pressurized.

[0083] Figure 8I illustrates the opening of the gap in the cut pipeline, by reeling the separated upper cut end of the pipeline upwards and back onto the pipe storage drum.

[0084] Figure 8J illustrates introduction of a transfer head or an A&R (abandonment and recovery) head into the space made by the separation enabled by the upward movement of the separated upper end of the pipeline.

[0085] Figure 8K illustrates the transfer head or A&R head welded onto the Separated Lower Cut End of pipeline hanging in the Hold Off / Hang Off clamp which is then transferred over to the FPSO or wet stored on the seabed.

[0086] Figure 8L illustrates the welding on of the next initiation head onto the Separated Upper Cut End at the lower work station.

[0087] Figure 8M illustrates pull down wire connected onto the initiation head ready for start of the second pipelay string, while the plug is unset and the Isolation Train walks robotically up the riser pipe, around the Reel Aligner Straightener and towards its preferred location in the nearly horizontal catenary.

[0088] Figure 8N illustrates the Isolation Train is now at its preferred location midway between the Reel Aligner Straightener and the Pipe Storage Drum.

[0089] Figure 9A illustrates the lower element of an Isolation T rain whereby the plug in the Isolation Train has been set to retain both pressure and fluid within the pipe going back towards the Pipe Storage Drum and that this Separated Upper Cut End has been moved to a position equivalent to the bottom of the Upper Tensioner.

[0090] Figure 9B illustrates the Lower Tensioner being prepared for opening. Figure 9C illustrates the Lower Tensioner opened and moved back to provide space for the In Line Structure.

[0091] Figure 9D illustrates the lower stub spool of the In Line Structure has been welded onto the top of the Separated Lower Cut End of the pipeline being held in the Hold Off / Hang Off Clamp.

[0092] Figure 9E illustrates the In Line Structure being lowered subsea, within the riser pipe string.

[0093] Detailed Description

[0094] Various embodiments of the present invention will be described in detail with reference to the drawings, where like reference numerals represent like parts and assemblies throughout the several views.

[0095] It will be appreciated that the invention should not be construed to be limited to the examples, which are now described; rather, the invention is construed to include all applications provided herein and all equivalent variations within the skill of the ordinary artisan.

[0096] Embodiments of the present invention will now be described with reference to the listed numbering and letter:

[0097] 102 Fluid / Pressure Injection Valve on Drum

[0098] 104 Pipe Storage Drum

[0099] 106 Pipe Horizontal Catenary

[0100] 108 Isolation Train

[0101] 110 Propulsor

[0102] 112 Plug

[0103] 114 Positioner

[0104] 116 Reel Aligner Straightener

[0105] 118 Lay T ower

[0106] 120 Upper Tensioner

[0107] 122 Lower Tensioner

[0108] 124 Pipe Vertical Riser 126 Upper Workstation

[0109] 128 Lower Workstation

[0110] 130 Hold Off / Hang Off Clamp

[0111] 132 Moon pool

[0112] 134 Hot Tap & vent

[0113] 136 Cut

[0114] 138 Separated Upper cut end

[0115] 140 Separated Lower cut end

[0116] 142 Water Pressure Injection Valve on Pig Launcher Receiver

[0117] 144 Cleaning Gauging Watering Pig Train

[0118] 146 Isolation Valve in Spool Piece welded to end of final stalk

[0119] 148 Connecting Flanges

[0120] 150 Receiver / Launcher

[0121] 152 Vent on PLR (Pig Launcher Receiver)

[0122] 154 Initiation Head

[0123] 156 Initiation pull down wire

[0124] 158 Seabed Foundation / Startup Anchor

[0125] 160 In Line Structure (PLET / PLEM / IN-LINE Tee)

[0126] 162 Handbrake Pad Set

[0127] 164 A&R Head or Transfer Head

[0128] 166 Mechanically Lined Pipe

[0129] 168 Propulsor Control Pod

[0130] 170 Plug Control Pod

[0131] 172 Positioner Control Pod

[0132] 174 Spring Loaded Wheel Sets

[0133] 176 Articulated Ball Joints

[0134] 178 Packer

[0135] 180 Bowl

[0136] 182 Grips

[0137] 184 Leading Pad Set

[0138] 186 Following Pad Set

[0139] 188 Long Piston Driving Ram

[0140] 190 Spool Base

[0141] 192 Reel Lay Vessel

[0142] 194 Propulsor Housing 196 Twin Thruster Prop Motor

[0143] 198 Twin Thruster Prop

[0144] S Seabed

[0145] Referring to the drawings, in Figure 1 , there is shown a Reel Pipe Lay vessel, installing a pipeline on the seabed, containing an In Line Structure which depends on an Isolation Train which contains a Pipeline Propulsor coupled to an Isolation Plug and a robotic Positioner which working together enables this improved method.

[0146] A common requirement during reeled pipelay operations is the need for internal isolation actions. This allows mechanically lined pipe (MLP) to maintain pressure while a laid section is hung off, depressurized, cut off, and re-terminated.

[0147] The pipeline system 100 comprises several key components, including a Reel Aligner Straightener 116 positioned on a Lay Tower 118 (Fig 2A), Mechanically Lined Pipe 166, a Pipe Storage Drum 104, Upper Tensioner 120, Lower Tensioner 122, Upper Work Station 126 and Lower Work Station 128 and other supporting structures (not shown). The Pipe Vertical Riser 124 is a segment of the Mechanically Lined Pipeline 166 extending between the seabed S and the Reel Aligner Straightener 116 while the Pipe Horizontal Catenary 106 extends between the Reel Aligner Straightener 116 and the Pipe Storage Drum 104. Also disclosed is the Fluid Pressure / lnjection valve on the Pipe Storage Drum 104, an In Line Structure 160 and a Seabed Foundation Start Up Anchor 158.

[0148] In accordance with embodiments of the invention, the Isolation Train 108 consists of an autonomous isolation Plug 112, a robotic walking Positioner tool 114 to move the Isolation Train 108 up the top of the Pipe Vertical Riser 124 over the Reel Aligner Straightener 116, and into the Pipe Horizontal Catenary 106. The Propulsor 110, coupled to the other Isolation Train 108 units, is used to propulse or swim the Isolation Train 108 from ahead and pull the Isolation Train 108 along inside the Pipe Horizontal Catenary 106 to maintain preferred locational position during reeled pipe lay.

[0149] In use, the Isolation Train 108, is pre-installed within a Receiver / Launcher 150 as described in reeling process of WO2011 / 051221A and is walked into the trailing end of the of the very last pipeline stalk to be reeled onboard the Reel Lay Vessel 192 to its Pipe Storage Drum 104. The Isolation Train’s 108 (Plug 112) is then hydraulically set in the last pipe joint end of the final pipe stalk, to confine all of the water inside the Mechanically Lined Pipe 166 to be reeled. This allows the spool base Receiver / Launcher 150 to be disconnected, in order to enable an Initiation Head 154 or other preferred structure to be installed on the end of the final stalk.

[0150] The Isolation Train’s 108 (Plug 112) is then unset, and the Isolation Train 108 (Propulser 110) swims approximately 100 metres up the water filled, dead headed last pipeline stalk to a defined location and stops. The Isolation Train 108, (Positioner 114) Hand-Brake Pad Set 162, is then applied. The Hand Brake Pad Set 162 is a hydraulic engagement system within the Positioner 114 of the Isolation Train 108 which mechanically locks the Isolation Train 108 to the Mechanically Lined Pipeline 166 internal wall. The Mechanically Lined Pipeline 166 is then pressurized to 30-50 bar or greater and it’s final pipe stalk of 1000m or thereabouts, is reeled onboard the Reel Lay Vessel 192, from the Spool Base 190. The Isolation Train 108 should then arrive at its preferred location within the midpoint in the Pipe Horizontal Catenary 106 between the Reel Aligner Straightener 116 and the Pipe Storage Drum 104.

[0151] The Reel Lay Vessel 192 sails to the field. The Initiation Head 154, Pull Down Wire 156 is reeved through the Seabed Foundation I Start Up Anchor 158 and back to the vessel winch where it is connected to the pipeline Initiation Head 154. The Isolation Train 108 hydraulic Hand Brake Pad Set 162 is dis-engaged from the Mechanically Lined Pipeline wall 166 and the Isolation Train 108 switches into Propulsor 110 mode. When in Propulsor 110 mode, the Isolation Train maintains position within the Pipe Horizontal Catenary 106 between the Reel Aligner Straightener 116 and the Pipe Storage Drum 104. The Initiation Head 154 on the Mechanically Lined Pipe 166 is pulled against the Seabed Foundation / Startup Anchor and pipe is fed through the Upper Tensioner 120 and Lower Tensioner 122 through the Moon Pool 132 to the seabed, and pipeline reel lay commences. The Isolation Train 108 maintains its preferred nearly horizontal position within the Pipe Horizontal Catenary 106 between the Reel Aligner Straightener 116 and the Pipe Storage Drum 104 throughout most of the pipelay activity.

[0152] Approximately 80 metres from final completion of the first flowline, the Isolation Train 108 engages again the Positioner’s hydraulic Hand Brake Pad Set 162 and thus the Isolation Train 108 now being mechanically connected to the internal wall of the Mechanically Lined Pipe 166, is relocated by the next 80 metres of reel lay pipe movement, from the Pipe Horizontal Catenary 106, position to a preferred position in the Pipe Vertical Riser 124, approximately above the Hold Off / Hang Off clamp 130. The autonomous isolation Plug 112 within the Isolation Train 108 is then hydraulically set, in the optimum vertical position, and the Hold Off I Hang Off Clamp 130 on the vessel work deck is locked tightly around the Pipe Vertical Riser 124 which then securely suspends the laid Mechanically Lined Pipe 166, above the seabed. The section of pipe above the Hold Off / Hang Off Clamp 130 and below the set Plug 112 in the Isolation Train 108 is hot tapped and vented 134, and the pipe section above the set Plug 112 back to the Pipe Storage Drum 104, remains pressurised. Subsequently, the pipe above the Hold Off / Hang Off Clamp 130, is cut, and the Separated Upper Cut End 138 is back-reeled towards and onto the Pipe Storage Drum 104, until sufficient space opens up, above the Separated Lower Cut End 140, to enable the next appurtenance such as a Transfer Head 164 or In Line Structure 160 to be installed.

[0153] The required appurtenance is welded onto the top of the Separated Lower Cut End 140 (top of the riser pipe suspended in the Hold Off / Hang Off Clamp 130. Once welded, the hanging pipe is transferred to a Floating Production, Storage, and Offloading (FPSO) vessel, or the hanging pipe with an A&R (Abandonment and Recovery) head can be lowered to the seabed for wet storage.

[0154] If a large In Line Structure 160 is to be installed in the pipeline being laid, as described in W02022 / 0042624A the Lower Tensioner tracks 122 are opened to make space available in the Lay Tower 118 area, and the Pipeline End Termination (PLET) or a Pipeline End Manifold (PLEM) or an in-line TEE or the required appurtenance is craned into position, hung off, and then welded onto the top end of the Separated Lower Cut End 140, which is locked in the Hold Off / Hang Off clamp 130. The In Line Structure 160 is then filled to below the HAZ (Heat Affected Zone) in the stub spool in its upper reaches and the Mechanically Lined Pipe 166 on the Pipe Storage Drum 104 is lowered to mate with this upper stub spool of the ILS 160 where it is welded. The Flowline End Termination (FLET), PLET, PLEM or In-line TEE, is then configured for lowering to the seabed.

[0155] With all pipe movement stopped the pressure across the Isolation Train 108 is equalized and the Plug 112 within the Isolation Train 108 is unset. The Positioner 114 within the Isolation Train 108 then robotically moves the Isolation Train 108 up the riser, around the Reel Aligner Straightener 116 and into it’s preferred Pipe Horizontal Catenary 106 location. The Mechanically Lined Pipe 166 is then re-pressurised and Reel Lay Operations can then recommence, with the lowering of the In Line Structure 160 to the seabed. If just a new Initiation Head or (A&R) Head 154 is being welded onto the new Separated Upper Cut End 138, then any vertical riser void space between the back of the Isolation Train 108 and the new Initiation Head or (A&R) Head 154 is filled with water up to below the HAZ (before the welding commences). The by-pass in the Isolation Train 108 is opened and the short Initiation Head 154 or (A&R) Head is then pressurized from the Fluid / Pressure Injection Valve 102 located on the cheek of the Pipe Storage Drum 104.

[0156] The isolation Plug 112 within the Isolation Train 108 is then unset, and the robotic walking tool Positioner 114 is used to move the now unset autonomous Isolation Train 108 up to and around the Reel Aligner Straightener 116, to reposition it in the preferred nearly horizontal location in the catenary between Reel Aligner Straightener 116 and the and the Pipe Storage Drum 104 for the next phase. The reel lay operation can then resume.

[0157] Emergency abandonment or weather driven lay down can be conducted quickly using the Propulsor, Plug, Positioner system. As soon as it is decided to lay down - the Isolation T rain 108 Hand Brake Pad Set 162 is hydraulically locked to the pipe wall. With lay speeds of 1000 metres per hour, the Isolation Train 108 will be in optimum vertical location at the Lower Work Station 128 in approximately 8 minutes. Once in the preferred vertical position, the Plug 112 within the Isolation Train 108 is SET, and the section below the Isolation Train is held within the Hold Off / Hang Off Clamp 130. The lower section is hot tapped just above the Hold Off / Hang Off Clamp 130 and pressure below the Isolation Train 108 is released. The pipe is then Cut 136 above the Hold Off / Hang Off Clamp 130. The Separated Upper Cut End 138, wherein its pressure is held by the Isolation Train’s Plug 112, can now be back reeled upwards, to provide space to fit the Initiation Head 154 (or Abandonment and Recovery) head. The A&R head is then welded to the Separated Lower Cut End 140, and this hung off pipe section is then consigned in a controlled manner to the sea bed. The SET Plug 112 within the Isolation Train 108 will remain in place at the bottom of the Pipe Vertical Riser 124, holding pressure and containing fluid within the section of Mechanically Lined Pipeline 166 going back to the Pipe Storage Drum 104. until it is time to recommence reel lay operations. When the weather abates the abandoned and submerged pipeline section is brought back through the Moon Pool 132 to surface with the recovery wire and is held in the Hold Off / Hang Off Clamp 130. It’s night cap (A&R head) is removed, and weld prepped. The previously Separated Upper Cut End (still pressurized) is lowered carefully down until it butts the face where the A&R head had been cut from. The two sections Separated Upper Cut End 138 and Separated Lower Cut End 140 are welded together and the by-pass within the Plug 112 in the Isolation Train 108 is opened to equalize pressure. When all Mechanically Lined Pipe 166 movement has stopped, the Plug 112 within the Isolation Train 108 is UNSET, and the Positioner 114 robotically walks the Isolation Train 108 up the Pipe Vertical Riser 124, and into its preferred horizontal position, in the catenary between the Reel Aligner Straightener 116 and the Pipe Storage Drum 104. The Positioner hydraulic hand brake pad set is then applied until it is time to recommence Reel Pipe Lay operations again, at which point, the Isolation Train 108 will switch back into 110 Propulsor mode.

[0158] Referring to the drawings, in Figure 2A, there is shown a reel lay operation in accordance with embodiments of the invention, generally referenced by numeral 100.

[0159] The Mechanically Lined Pipe 166 is being unreeled from a Pipe Storage Drum and being fed over the Reel Aligner Straightener 116 through an Upper Tensioner 120 and then through a Lower Tensioner 122 into the Pipe Vertical Riser 124 orientation, where it can be accessed by the Upper Workstation 126 and the Lower Workstation 128 before it passes through the Hold Off / Hang Off Clamp area 130 through the Moon Pool 132 and subsea. Furthermore, there is seen an In Line Structure 160 which could consist of a Pipe Line End Termination (PLET), a Pipe Line End Manifold (PLEM), or an In Line Tee (ILT). Also shown is the Seabed Foundation / Start Up Anchor 158 and the Seabed S.

[0160] Figure 2B shows the preferred location of the Isolation Train throughout all Pipe Laying operations within the (nearly) Pipe Horizontal Catenary 106. The Isolation Train 108 will maintain this location through various dynamic position keeping methods, which are interfaced into its Propulsor 110 Control Pod system 168.

[0161] Figure 3 indicates the Isolation Train 108 with its three coupled systems - Propulsor 110, Plug 112 and Positioner 114. All three systems are mechanically interconnected with articulating ball joints, and all three systems are centralized on sprung loaded wheel sets to hold them axially central within the Mechanically Lined Pipeline 166.

[0162] Figure 4A shows one description of the Propulsor 110 (which can be a motor driven prop system, a Ducted Impeller arrangement or a Jet Pump). All three propulsor systems take advantage of operating within ducted open fluid flows, while being confined inside the also ducted, dead headed water column of the water filled and pressurized, Mechanically Lined Pipe 166.

[0163] Figure 4B shows a perspective view of the Propulsor 110 and its Propulsor Control Pod 168 which provides ELF communication to and from the Propulsor 110 as well as command and control processes to Propulsor to maintain its position within the Pipe Horizontal Catenary 106 during pipe lay operations.

[0164] Figure 4C and 4D provide further presentations of aspects of the Propulsor 110, the Propulsor Housing 194 (for Prop I Impeller or Jet Pump - in this depiction twin Thruster Props 198 are shown) Thruster Props 198 can be configured in line, with defined separation, as well as nested side by side, as in this case. Twin Thruster Prop Motors 196 are shown which drive ducted Thruster Props 198, positioned strategically at the leading end of the Isolation Train 108. This design ensures efficient propulsion. Propulsor 110 is mounted within Spring Loaded Wheel Sets 174, which are rubber surfaced, to run smoothly within the confines of the Mechanically Lined Pipe 166. Propulsor’s 110 drive system, is appropriately sized to actively generate the required thrust to ensure effective movement of the Isolation Train’s 108 mass, as well as minimizing vortex formation. Additionally, a propellor boss or nose cone enhances hydrodynamic efficiency by reducing drag and improving flow dynamics. These components collectively optimize the propulsor’s alignment and streamline its movement within the pipeline. It's underwater motors, along with fluidlubrication coolant vanes, form a robust system which prevents overheating.

[0165] Figure 4E gives a perspective view of Propulsor 110 showing the Propulsor Housing 194 the Spring Loaded Wheel Sets 174 and the Articulated Ball Joints 176 which enable the various components which make up the Isolation Plug Train 108 to move through the Mechanically Lined Pipe 166 Reel Aligner Straightener 116, and it’s long radius bend. This collaborative functionality allows Propulsor to operate with precision and reliability within the pressurised Mechanically Lined Pipe 166 environment.

[0166] Figure 5 shows the autonomous isolation Plug 112 module of the Isolation Train 108 and indicates where its Packer 178, Bowl ramp 180 and Grips 182 are located. The Plug Control Pod 170 contains the communications, electronics, hydraulics and valving systems which hydraulically set and unset the isolation Plug 112 Figure 6A shows Positioner 114 which contains the hydraulically activated Leading Pad Set 184, the hydraulically activated Following Pad System 186 and the sprung loaded but hydraulically deactivated Hand Brake Pad System 162. The Long Piston Driving Ram strokes 500mm for each expanding movement. The Positioner Control Pod 172 contains advanced communication and power management systems for precise positioning throughout reel pipe lay operations. The Positioner Control Pod 172 contains the hydraulic systems and controls necessary to operate Positioner 114. All of Positioner’s pad systems: the Leading Pad System 184, Following Pad System 186 and Hand Brake Pad System 162, are maintained axially central by the Spring Loaded Wheel Sets 174 and modules are allowed to flex by the Articulated Ball Joints 176. The Positioner robot 114, plays a pivotal role in the Isolation Train configuration 108, strategically moving and positioning the autonomous isolation Plug 112 and Propulsor 110 in defined conditions such as within vertical riser configurations, making movement adjustments of the Isolation Train 108 for precision reasons or for example robotically exiting the spool base Receiver / Launcher 150 when entering the end of the Stub Spool Piece with integrated ball valve welded to end of final stalk 146, without pigging medium. Positioner 114’s modular design ensures adaptability to various pipeline sizes and In Line Structure 160 configurations.

[0167] Figure 6B shows Positioner 114 with its Long Piston Driving Ram 188 extended. Propulsor 114 provides axial movement along the pipe by conducting the following sequence: Retracting its Leading Pad System 184 from the Mechanically Lined Pipe 166 wall.

[0168] Extending its Long Piston Driving Ram 188 up the Mechanically Lined Pipe 166 Extending its Leading Pad System 184 back onto the Mechanically Line Pipe 166 wall Retracting its Following Pad System 186 from the Mechanically Lined Pipe 166 wall Disengaging the Hand Brake Pad System 162 from the Mechanically Lined Pipe 166 wall Retracting its Long Piston Driving Ram 188 up the Mechanically Lined Pipe 166 Re-engaging the Hand Brake Pad System 162 back onto the Mechanically Lined Pipe 166 wall

[0169] Extending its Following Pad System 186 back onto the Mechanically Lined Pipe 166 wall And repeating the process again. Each movement provides 500mm of stroke.

[0170] Figure 7A shows the Reel Lay Vessel 192 moored stern to the Spool Base 190

[0171] Figure 7B shows the leading tailing end of ordinary pipe has been locked onto the Pipe Storage Drum 104 with the vessel’s Lay Tower 118 rotated down to a non-vertical angle of 45 degrees to reduce the bending moment on the Mechanically Lined Pipe 166 when it is reeled on.

[0172] Figure 7C shows the Fluid Pressure Injection Valve 102 located on the Pipe Storage Drum cheek, normally within a radial manifold arrangement for injecting fluid (water or MEG) into the Mechanically Lined Pipe 166. The Cleaning Gauging Watering Pig Train 144 is located at the very end of the leading pipe string and it is pigged by water or MEG down the line, to the Spool Base 190, to the end of the first stalk, which is then pressurized to 30 to 50 bar or greater, before the Mechanically Lined Pipe 166 is reeled on.

[0173] This prior art is well described in WO 2008 / 072970 A1 (Statoil) a. Fill with fluid, pressurize and reel b. A further pipeline section is joined to the section already reeled onto the pipe laying drum, whilst the pipeline is motionless without mechanical movement, as the overpressure can be relieved as long as the sections are without mechanical movement c. An overpressure of 5-25 bar is applied within the sections and the further section is reeled onto the pipe laying drum. d. Several sections are joined together and reeled on until the predetermined pipeline length is achieved. e. The pipeline is laid from the vessel onto the seabed whilst an overpressure of 5-25 bar is maintained within the pipeline by means of pressurized fluid.

[0174] This prior art process is used until Figure 7D

[0175] Figure 7D shows the Cleaning Gauging Watering Pig Train 144 arriving at the final end of the last Mechanically Lined Pipeline 166 stalk, to be reeled onto the Reel Lay Vessel 192.

[0176] Figure 7E shows the Cleaning Gauging Watering Pig Train 144 has been pigged into the Receiver Launcher 150, past the Stub Spool Piece with Integrated Ball Valve 146, which is welded to end of final stalk. The Ball Valve 146 is shut and the Receiver / Launcher 150 is vented at the Vent on the PLR (Pig Launcher Receiver) 152, and the Bolted Flange 148 joining the Receiver / Launcher 150 to the Stub Spool 146 is split and then the Cleaning Gauging Watering Pig Train 144 is removed from the Receiver / Launcher 150.

[0177] Figure 7F shows the Isolation Train 108 has been installed into the Receiver Launcher 150, and the Bolted Flange 148 has been made up and the Receiver Launcher 150 has been filled with fluid and pressurized to balance the stalk pressure Figure 7G shows the Isolation Train 108 has robotically walked out of the Receiver / Launcher 150 into the end of the pipeline stalk past the Stub Spool Piece with Integrated Ball Valve 146 which has been opened and has stopped past the weld which joins the Stub Spool Piece with Integrated Ball Valve 146 onto the end stalk of the Mechanically Lined Pipeline 166 where its Plug 112 is hydraulically set.

[0178] Figure 7H shows the Isolation T rain 108 holding back the water fluid within the Mechanically Lined Pipe 166 whereby the weld joining the Stub Spool Piece with Integrated Ball Valve 146 is cut off, and the Receiver / Launcher 150 with bolted on Stub Spool Piece with Integrated Ball Valve 146 are moved clear.

[0179] Figure 7I shows the Initiation Head 154 has been welded onto the end of the Mechanically Lined Pipe 166 and the Plug 112 within the Isolation Train 108 is then unset.

[0180] Figure 7J shows that the Propulsor 110 within the Isolation Train 108 has propelled the Isolation Train 108, 80 metres to a pre-determined position within the pipeline stalk, where the Hand Brake Pad Set 162, within the Positioner 114 of the Isolation Train 108 has been engaged to lock the Isolation Train 108 to the Mechanically Lined Pipe 166 wall.

[0181] Figure 7K shows that the Mechanically Lined Pipe 166 has been pressurized and is being reeled onboard the Reel Lay Vessel 192. It shows the Isolation Train 108 which is Hand Brake Pad Set 162 locked into the pipe wall and has been reeled past both the Lower Tensioner 122 and the Upper Tensioner 120.

[0182] Figure 7L shows that the Isolation Train 108 has arrived at its Pipe Horizontal Catenary 106 location and that the Initiation Head 154 has simultaneously arrived at the predetermined location at the Moon Pool 132 work area. Note: if an In Line Structure 160 such as a PLET (Pipe Line End Termination) or a PLEM (Pipe Line End Manifold) was to be pre-installed on the Mechanically Lined Pipe 166 to go down onto the Seabed S first, then the Isolation Train 108 would have been retained at the very end of the final stalk, in a Plug 112 set condition, and there would be no requirement to install an Initiation Head 154 before reeling on, and no requirement for Propulsor 110 to propel the Isolation Train 108, 80 meters up the line. Figure 8A shows initiation of reel lay operations. The Initiation Pull Down Wire 156 is reeved through the Seabed Foundation / Start Up Anchor 158 and the Initiation Head 154 is made ready for pulling down to the Seabed S,

[0183] Figure 8B shows the Hand Brake Pad System 162 on Positioner 114 within the Isolation Train 108 is released from the Mechanically Lined Pipe 166 wall and the Isolation Train switches into Propulsor 110 mode within the Pipe Horizontal Catenary 106, and then reel lay operations can commence.

[0184] Figure 8C shows the location within the Pipe Horizontal Catenary 106 where the Isolation Train 108, now in Propulsor 110 mode, will keep station throughout the reel lay operations

[0185] Figure 8D Approximately eighty metres (or a pre-determined distance) from the defined Hold Off / Hang Off Clamp 130, Cut Point 136, the Isolation Train 108 switches from Propulsor 110 mode, to Positioner 114 mode and activates its Hand Brake Pad System 162 which brings the Isolation Train 108 from the Pipe Horizontal Catenary 106 into the Pipe Vertical Riser 124 adjacent to the Lower Work Station 128.

[0186] Figure 8E Depicts the activation of the Hold Off / Hang Off clamp 130 which securely captures the Mechanically Lined Pipe 166

[0187] Figure 8F Shows the hydraulic activation of the Plug 112 in the Pipe Vertical Riser 124, which is pressurised. The Plug 112 is set, and the pressure ahead of the Plug 112 all the way to the Pipe Storage Drum 104 is contained by its grips and packer sealing system.

[0188] Figure 8G Shows the hot tap and vent activity which is necessary to remove the pressure in the Pipe Vertical Riser 124, before the Mechanically Lined Pipe 166 can be cut.

[0189] Figure 8H Depicts the Cut 136 of the pipe below the set isolation Plug 112, where it has been depressurized by the Hot Tap 134 activity.

[0190] Figure 8I Shows the opening of the gap in the cut pipeline, by reeling the separated upper cut end of the pipeline upwards and back onto the pipe storage drum. The lower section remains securely captured within the Hold Off / Hang Off Clamp 130. Figure 8J A transfer head or an A&R (abandonment and recovery) Head 164 is introduced into the space made by the separation enabled by the upward movement of the Separated Upper Cut End 138 from the Separated Lower Cut End 140.

[0191] Figure 8K Shows the transfer head or A&R Head 164 welded onto the Separated Lower Cut End 140 of pipeline hanging in the Hold Off / Hang Off clamp 130 which is then transferred over to the FPSO or wet stored on the seabed.

[0192] Figure 8L illustrates the welding on of the next Initiation Head 154 onto the Separated Upper Cut End 138 at the Lower Work Station 128.

[0193] Figure 8M Shows Pull Down Wire 156 of the Initiation Head 154 ready for start of the second pipelay string, while the isolation Plug 112 is unset and the Isolation Train 108 walks robotically up the riser pipe, around the Reel Aligner Straightener 116 and onwards to its preferred location in the nearly horizontal Pipe Horizontal Catenary 106 location.

[0194] Figure 8N Shows the Isolation Train 108 is now relocated at its Pipe Horizontal Catenary 106 location midway between the Reel Aligner Straightener 116 and the Pipe Storage Drum 104. Note that unplanned lay down operations (for deteriorating weather etc) are conducted as per the sequence for normal reeled pipe lay, up to and including Step 8K. The pipe is then laid down on the Seabed S in a controlled manner for later recovery when weather conditions improve.

[0195] Figure 9A Installation of an In Line Structural 60, such as a PLET (Pipe Line End Termination) PLEM (Pipe Line End Manifold) or ILT (In Line Tee) follows the same sequence as normal reeled pipe lay until reaching this step which shows the lower element of the Isolation Train 108 whereby the isolation Plug 112 within the Isolation Train 108 has been set to retain both pressure and fluid within the pipe going back towards the Pipe Storage Drum 104 and that this Separated Upper Cut End 138 has been moved to a position equivalent to the bottom of the Upper Tensioner 120.

[0196] Figure 9B Shows the Lower Tensioner 122 being prepared for opening, as the heavy In Line Structure 160 demands a large clear hang off area. Figure 9C Depicts the Lower Tensioner 122 opened and moved back to provide space for the In Line Structure 160.

[0197] Figure 9D illustrates the In Line Structure 160 has been craned off the deck and rotated through 90 degrees into a fit up position, whereby the lower stub spool of the In Line Structure 160 can be welded onto the top of the Separated Lower Cut End 140 of the pipeline being held securely in the Hold Off / Hang Off Clamp 130. At this point the In Line Structure 160 is filled with fluid, up to just below the HAZ on the upper stub spool of the In Line Structure 160. The upper riser pipe section (ahead of the set Plug 112, and all the way to the Pipe Storage Drum 104) which is still pressurized, is then lowered carefully until the previously Separated Upper Cut End 138 mates with the upper stub spool of the In Line Structure 160 which is then welded. On completion of welding, the Plug 112 within the Isolation Train 108 is then unset and it switches into Positioner 114 mode, and robotically walks up the Pipe Vertical Riser 124, around the Reel Aligner Straightener 116 and into its preferred position in the Pipe Horizontal Catenary 106. The Isolation Train 108 is then ready to switch over to Propulsor 110 mode, and to recommence reel pipe lay and lowering the In Line Structure 160 to the Seabed S

[0198] Figure 9E illustrates the In Line Structure being lowered subsea, within the riser pipe string, while the Isolation Train 108 maintains its dynamic position in the Pipe Horizontal Catenary 106.

[0199] It is to be understood that the invention is not limited to the specific details described herein which are given by way of example only and that various modifications and alterations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1. An improved method of executing reeled pipelay of mechanically lined pipe including; inserting an isolation plug train inside the pipe, the isolation plug train including an isolation plug and a robotic positioner coupled together and to a pipeline propulsor by articulated ball joints; applying internal hydrostatic pressure up to a range of approximately 30-120 bar to the pipe; deploying and activating the isolation train in the pressurised pipe to maintain the internal hydrostatic pressure adjacent an end of the pipe being cut to prevent loss of pressure and enabling the pipe to be reeled back under pressure at any stage of the lay operation removing the risk of wrinkling the lining of the pipe.

2. An improved method of executing reeled pipelay of mechanically lined pipe as claimed in Claim 1 , including deploying and activating the isolation train to maintain internal pressure in the pipe to prevent the introduction of air pockets into the pipe when connecting in line structures to the pipe, the in line structures including pipe line end terminations, pipe line end manifolds, in line trees and the like.

3. An improved method of executing reeled pipelay of mechanically lined pipe as claimed in Claim 2, including deploying and activating the isolation tool in a riser string of the pipe during the connection of one of the line structures to the pipe in a manner which alleviates the requirement to reflood and re-pressurise the riser string.

4. An improved method of executing reeled pipelay of mechanically lined pipe as claimed in any one of the preceding claims, including deploying and activating the isolation tool in the pipe in deteriorating weather in a manner which maintains pressure in the pipe during a back reeling operation.

5. An improved method of executing reeled pipelay of mechanically lined pipe as claimed in any one of the preceding claims, including operating the pipeline propulsor to facilitate autonomous movement of the isolation plug train to create an internal stop in the pipeline when required and to maintain a predetermined pressurelevel over a designated section of the pipeline, so as to prevent wrinkling of the mechanically lined pipe.

6. An improved method of executing reeled pipelay of mechanically lined pipe as claimed in Claim 5, including autonomously tracking and positioning the pipeline propulsor to maintain autonomous movement to ensure it generally maintains a desired specific position in a catenary between a reel storage drum and a reel aligner straightener mounted on a vessel, during laying of the pipeline.

7. An improved method of executing reeled pipelay of mechanically lined pipe as claimed in Claim 6, including activating the pipeline positioner to move the pipeline isolation train over the reel aligner straightener into an optimum vertical position in the pipeline, setting the plug within the isolation train to maintain the pressure in the pipeline, holding a lower section of the pipe below the isolation train in a hold off I hang off clamp, hot tapping the pipeline above the clamp to release the pressure in the pipe below the isolation train, cutting the pipe above the clamp and back reeling the pressured pipe onto the drum at the desired distance to enable subsequent procedures to be performed as required.

8. A pipeline propulsor for coupling to an isolation train adapted to be inserted in a mechanically lined pipe for use in a method as claimed in any one of the preceding claims, the pipeline propulsor including: an enclosed rotor system operable to move the propulsor within the pipeline, and; a fluid-cooled propulsion system, operable to drive the enclosed rotor system; wherein said pipeline propulsor is operable to facilitate effective, autonomous movement of one or more pipeline tools attached to the propulsor, within the isolation train configuration.

9. The pipeline propulsor of claim 8, wherein the fluid-cooled propulsion system is embodied as a fluid-cooled electric motor.

10. The pipeline propulsor of claim 9, wherein the enclosed rotor system is configured as an enclosed impeller, mounted perpendicular to the pipeline axis, positioned either at an operatively fore or an operatively rear end of the propulsor.

11. The pipeline propulsor of claim 9, further comprising multiple spring-loaded wheels, maintaining axial centralization and preventing rotation of the train configuration.

12. The pipeline propulsor of claim 8, wherein the enclosed rotor system is a ducted propeller unit, positioned at either an operatively fore or an operatively rear end of the propulsor, and placed at the operatively fore end of the train configuration in specific embodiments.

13. The pipeline propulsor of claim 8, wherein the fluid-cooled propulsion system is a fluid-cooled jet propulsion system, including an inlet, a duct, a shaft, a propeller, one or more stators, an intake nozzle, and an outflow nozzle outlet.

14. The pipeline propulsor of claim 13, wherein the inlet is positioned inside the pipeline fluid, maintaining circular symmetry and a constant geometry to reduce hydraulic losses and outlet vortex issues.

15. The pipeline propulsor of claim 8, operable to facilitate autonomous movement of one or more pipeline tools, including a double block and bleed multi-set autonomous pipeline isolation tool and a robotic walking tool for moving the isolation tool precise distances within the pipeline.

16. The pipeline propulsor of claim 15, further operable to create an internal stop in the pipeline to maintain a predetermined pressure level over a designated section, eliminating wrinkling or liner buckling in mechanically lined pipes during reel lay operations.

17. The pipeline propulsor of claim 8, incorporating a separate power source, with specific energy characteristics tailored to the propulsor's demands.

18. The pipeline propulsor of claim 8, equipped with a control means, including an electronic speed controller and / or a power switch, enabling flexible control of the autonomous isolation plug train movement within the pipeline.

19. The pipeline propulsor of claim 8, including one or more ball joints coupled at a preferred distance from an operatively rear or fore end of the train configuration.

20. The pipeline propulsor of claim 8, sized in relation to the inner diameter of the pipeline, ensuring efficiency in consideration of viscous drag and fluid passage.

21. The pipeline propulsor of claim 8, incorporating an autonomous tracking and positioning system, with options of using isotopes, or Extremely Low Frequency (ELF) pingers, or acoustic pingers, inclinometers, inertial navigation systems, or a combination thereof.

22. The pipeline propulsor of claim 21 , using isotopes with scintillating detectors, ELF pingers with null point receivers, acoustic receivers, or inclinometers or inertial navigation systems for autonomous tracking and positioning.

23. The pipeline propulsor of claim 21 , incorporating a hybrid system, combining magnetic pinger beacons, null point receivers, inclinometers, inertial navigations systems, and thrusters for enhanced autonomous tracking and positioning.

24. The pipeline propulsor of claim 8, operable within a non-fluid pipeline system, provided in the form of a nitrogen-purged gas turbine propulsor.

25. The pipeline propulsor of claim 8, enabling effective autonomous movement of more than one variety of pipeline tools or an autonomous isolation plug train within a deepwater reel lay pipe-laying system.

26. The pipeline propulsor of claim 8, enabling effective autonomous movement of more than one variety of pipeline tool, such as an autonomous isolation plug train, within any offshore or onshore, rigid or flexible, pipeline transportation system.

Images