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Title:
FLEXIBLE SUBSEA HYDROCARBON PIPELINE ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2017/042632
Kind Code:
A1
Abstract:
A flexible subsea hydrocarbon pipeline assembly comprising: - a flexible subsea hydrocarbon pipeline having an end fitting: and - a submersible pump wholly or partly located and locked in the end fitting. The integration of a submersible pump with a flexible pipeline structure significantly increases the usability of the combined assembly in offshore and subsea hydrocarbon production, whilst avoiding the problems of requiring separate or external power supplies.

Inventors:
MISAN, Marek (10a Veros Place, Marangaroo, Western Australia WA 6065, WA 6065, AU)
YEO, Eng-Hui (3 Ruffian Loop, Willetton, Western Australia WA6155, WA6155, AU)
SEGATTO DE HAAN PORTO, Karina (23/6 Hampton Street, Burswood, Western Australia WA6100, WA6100, AU)
MORAND, Henri (87 Rua Julio de Castihos, Apto 102Copacabana, RJ -025 Rio de Janeiro, RJ 22081-025, BR)
TRAN, Erik (37 Majestic Parade, Dianella, Western Australia WA6059, WA6059, AU)
Application Number:
IB2016/001432
Publication Date:
March 16, 2017
Filing Date:
September 06, 2016
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
TECHNIP FRANCE (6-8 Allée de l'Arche, Faubourg de l'ArcheZAC Danton, Courbevoie, 92400, FR)
International Classes:
E21B43/12; E21B17/20; F16L11/00
Domestic Patent References:
WO2015121616A12015-08-20
WO2014079455A12014-05-30
Foreign References:
US20130068465A12013-03-21
US20030170077A12003-09-11
FR2863650A12005-06-17
Attorney, Agent or Firm:
RICHAUD, Fabien (Cabinet Murgitroyd, Immeuble Atlantis55 Allée Pierre Ziller - CS, 06902 Valbonne Sophia Antipolis, 06902, FR)
Download PDF:
Claims:
CLAIMS

1 . A flexible subsea hydrocarbon pipeline assembly comprising:

- a flexible subsea hydrocarbon pipeline having an end fitting: and

- a submersible pump wholly or partly located and locked in the end fitting.

2. A flexible subsea hydrocarbon pipeline assembly as claimed in claim 1 wherein the flexible subsea hydrocarbon pipeline is one of the group comprising: a riser, a flowline and a jumper.

3. A flexible subsea hydrocarbon pipeline assembly as claimed in any one of the preceding claims wherein the flexible subsea hydrocarbon pipeline is an Integrated Production Bundle. 4. A flexible subsea hydrocarbon pipeline assembly as claimed in any one of the preceding claims wherein the submersible pump is an electrical submersible pump.

5. A flexible subsea hydrocarbon pipeline assembly as claimed in any one of claims 1 -3 wherein the submersible pump is a gas-powered submersible pump.

6. A flexible subsea hydrocarbon pipeline assembly as claimed in any one of the preceding claims wherein the end fitting includes a power docking station for the pump. 7. A flexible subsea hydrocarbon pipeline assembly as claimed in any one of the preceding claims wherein the submersible pump is separable from the end fitting.

8. A flexible subsea hydrocarbon pipeline assembly as claimed in any one of the preceding claims wherein the submersible pump is lockable in the end fitting using one or more of the group comprising; a nipple and mandrel tool, a spiral screw connection, and one or more hydraulic packers.

9. A flexible subsea hydrocarbon pipeline assembly as claimed in any one of the preceding claims wherein the submersible pump is powered using one or more penetrators in the end fitting.

10. A flexible subsea hydrocarbon pipeline assembly as claimed in claim 9 wherein the one or more penetrators are selected from the group comprising:

electrical penetrators, gas penetrators and hydraulic penetrators, and combinations thereof.

1 1 . A flexible subsea hydrocarbon pipeline assembly as claimed in any one of the preceding claims wherein the submersible pump is powered by one or more of power cables or gas lines provided from the flexible subsea hydrocarbon pipeline. 12. A flexible subsea hydrocarbon pipeline comprising a flexible subsea hydrocarbon pipeline as defined in any one of claims 1 to 1 1 and having an end fitting adapted to wholly or partly house a separable submersible pump.

13. A method of forming a flexible subsea hydrocarbon pipeline assembly as defined in any one of claims 1 to 12 comprising at least the steps of:

(i) providing a submersible pump;

(ii) locating the submersible pump in the end fitting of the flexible subsea hydrocarbon pipeline

(iii) locking the submersible pump into the end fitting: and

(iv) connecting the submersible pump to a power source.

14 A method as claimed in claim 13 wherein the submersible pump is an electrical submersible pump, and the power source is one or more power cables.

Description:
FLEXIBLE SUBSEA HYDROCARBON PIPELINE ASSEMBLY

The present invention relates to a flexible subsea hydrocarbon pipeline assembly, generally comprising a flexible subsea pipeline having an end fitting housing a submersible pump powered by the pipeline.

In the subsea production, provision and supply of hydrocarbons, generally from one or more offshore production wells in or on the seabed, the internal pressure required to transfer the hydrocarbons from the seabed to a suitable vessel, such as a floating production vessel at sea level, may require assistance. That is, some production wells have inadequate internal pressure to provide the whole pressure required to transfer the hydrocarbons to the sea surface. This problem is increasing as offshore wells are being drilled in deeper and deeper waters, now sometimes greater than 2000 metres deep, and possibly greater than 3000 metres deep.

The use of electrical submersible pumps (ESP) is well known in the art in order to assist or boost pressure and flow of hydrocarbons from at or near a seabed to sea level, generally through risers and the like. The ESP can also be used to increase the recovery fraction of a given reservoir.

ESPs generally comprise a pump run by an attached motor, (and optionally one or more gas/liquid separators, as the gas can be vented and rise to the sea surface elsewhere, such as in the annular space between a riser and the production pipeline or tubing).

US 6,412,562 B1 shows an electrical submersible pump assembly suspended within a riser. The riser extends upward from a well to near sea level, and the pump is suspended within the riser near the well end, optionally within the first 25 meters above the well head. An electrical motor is supported on the lower end of the seal section of the ESP, and it is a large AC motor supplied with electrical power through a power cable extending down from the floating production platform.

US 7,565,932 B2 shows a submersible pump assembly mounted in the straight portion of a flowline jumper engaged in a subsea production system. The pump assembly boosts pressure of fluid flowing between various receptacles on the seabed. The electrical motor for the submersible pipe assembly is powered by a power cable which has a penetrator that extends through a flange, and which is connected to a source of power, optionally subsea, such as a wet mate connector system located at a suitable manifold.

Each of the above assemblies requires separate power cables or a separate power source to drive the ESP, which increases installation time, maintenance, and possible hazards. Also, each of the above is a static structure that has no flexibility in use or positioning.

It is an object of the present invention to overcome one or more of the above problems. According to a first aspect of the present invention, there is provided a flexible subsea hydrocarbon pipeline assembly comprising:

- a flexible subsea hydrocarbon pipeline having an end fitting: and

- a submersible pump wholly or partly located and locked in the end fitting. The integration of a submersible pump within a flexible pipeline structure significantly increases the usability of the combined assembly in offshore and subsea

hydrocarbon production, whilst avoiding the problems of requiring separate or external power supplies, and requiring to be permanently suspended through a tether to the top of the flexible subsea hydrocarbon pipeline, generally at the hang-off level.

Flexible subsea hydrocarbon pipelines are well known in the art, and generally comprise a series of concentric but modular layers, starting with a first inner layer or carcass made of a hydrocarbon-resistant material such as stainless steel, surrounded by one or more pressure sheaths, one or more armour layers (generally being alternate cross layers), followed by an external sheath, generally formed of a suitable plastic such as polyamide. One or more of these layers may be formed of spirals, and they are generally laid in alternative directions to increase strength. A typical example is shown in Figure 1 of the accompanying drawings, and described hereinafter. Flexibility is a distinctive property of flexible subsea hydrocarbon pipelines, and for example helically wound steel wires used for forming the armour layers give such pipelines their high pressure resistance and excellent bending characteristics, providing flexibility and superior dynamic behaviour. Generally, such pipelines have a modular construction, where the layers are independent but designed to interact with one another. Flexible dynamic risers have been particularly useful in developing floating production systems, i.e. between the fixed sea floor or seabed structures, and the floating nature of the production system. Moreover, their flexibility makes it possible to spool flexible pipelines on and off reels for efficient and quick

transportation and installation.

Typical flexible subsea hydrocarbon pipelines are flowlines and risers. According to one embodiment of the present invention, the flexible subsea hydrocarbon pipeline is one or more of the group comprising: a riser, a flowline and a jumper.

A particular form of a flexible subsea hydrocarbon pipeline is termed an 'Integrated Production Bundle' or ΊΡΒ', in which the traditional structure of a flexible pipeline (with its modular layers as described above), is surrounded by one or more further layers, including but not limited to being one or more of the group comprising: tubes, hoses, cables and fillers - including optical fibres, electrical cables, packers, hydraulic hoses, gas lift tubes, and any combination of same. This structure is then further surrounded by one or more external sheaths, such as polymer sheaths. The additional layers in an IPB can provide umbilical component functionality to a standard flexible subsea hydrocarbon production fluid pipeline, such as (by way of example only): passive insulation and active heating in order to minimise the potentially significant thermal loses that can occur along the height of a riser;

the integration of several lines, such as production bore, gas lift and umbilical, into a single multi-bore pipeline, which reduces the congestion of the riser system and subsea equipment;

the amalgamation of gas lift/injection tubes; the possible addition of an optical fibre distributed temperature system for real time monitoring of the temperature along the riser; and

the continuing use of a core flexible pipe that still has a low bending radius, but which allows a greater range of installation vessels to be used with reduced top side operating tensions in deep water.

Thus, according to one embodiment of the present invention, the flexible subsea hydrocarbon pipeline is an Integrated Production Bundle. Submersible pumps are well known in the art, and typically comprise at least a pump intake for supplying the liquid to be pumped, a motor driving an internal pump mechanism after the pump intake, and a pump discharge.

According to one embodiment of the present invention, the submersible pump is an electrical submersible pump, i.e. the motor is an electric motor, and there are one or more electrical power sources. Electrical submersible pumps are well known in the art, and the problems with their prior use are described hereinabove.

According to another embodiment of the present invention, the submersible pump is a gas-powered submersible pump, i.e. the motor is gas-driven, and there are one or more sources of suitably high pressure gas. An example of a source of suitably high pressure gas is compressed gas provided within the flexible subsea hydrocarbon pipeline, such as one or more gas lift tubes. Gas lift tubes are used in some flexible subsea hydrocarbon pipelines, such as but not limited to an Integrated Production Bundle as described herein. The high pressure of the gas provided by the gas lift tube can also be partially used to run the pump, and the remaining pressure can be utilised for gas lift of the production fluid.

According to another embodiment of the present invention, the submersible pump is a hydraulic-powered submersible pump, i.e. the motor is hydraulically-driven, and there are one or more sources of hydraulic fluid. An example of a source of hydraulic fluid is a hydraulic fluid tube provided within the flexible subsea

hydrocarbon pipeline. Hydraulic fluid tubes are used in some flexible subsea hydrocarbon pipelines, such as but not limited to an Integrated Production Bundle as described herein. The submersible pump may comprise one or more of the group selected from:

pumps, pump mechanisms, seals, motors, motor connectors and other connectors. The pump may be any known arrangement involving impellers, screws, etc., optionally of the centrifugal type.

According to one embodiment of the present invention, the end fitting includes a power docking station for the pump. The power docking station may be integral or separable from the end fitting, and provides an intermediate station between the power source and the submersible pump. Optionally, the power docking station provides flexibility of design to the flexible subsea hydrocarbon pipeline assembly.

The end fitting location may be either at a subsea termination, etc. or at a flexible mid-line connection. The end fitting of the flexible subsea hydrocarbon pipeline may comprise any shape or design, generally having one or a first end mateable with the components of the flexible subsea hydrocarbon pipeline, and an opposite or second end being mateable to another complementary end fitting (to form a mid-line connection with another flexible pipeline), or mateable to one or more other production structures, in particular subsea production structures such as well heads or manifolds, etc. in the form of a jumper. Such connections are generally through the use of one or more bolts or bolt heads, and flange arrangements, known in the art. According to another embodiment of the present invention, the submersible pump is separable from the end fitting, such that the submersible pump may either be subsequently added to the end fitting after fitting of the flexible subsea hydrocarbon pipeline, or be removed from the end fitting (for maintenance or repair, etc.), or both. In this way, the flexible subsea hydrocarbon pipeline can still be installed and used in its standard form, and the present invention provides the flexibility of subsequently adding or removing a submersible pump thereinto where necessary or desired.

With increasing operating or seabed depths, and therefore increasing hydrocarbon travel distance, it may also be desired to locate more than one submersible pump between a seabed and sea level, and the present invention allows the introduction of a number of flexible subsea hydrocarbon pipelines in series, with the introduction of as many submersible pumps in suitable end fittings located between such pipelines (mid-line) as desired or necessary. Thus, the present invention provides flexibility to achieve complex or longer pipeline solutions.

According to a second aspect of the present invention, there is provided a flexible subsea hydrocarbon pipeline comprising a flexible subsea hydrocarbon pipeline having an end fitting adapted to wholly or partly house a separable submersible pump. Optionally, the flexible subsea hydrocarbon pipeline is an Integrated

Production Bundle.

Where the submersible pump can be separable from the end fitting, the submersible pump can be located and locked into an end fitting using one or more fitting or mating systems known in the art. These include one or more of the group

comprising: a nipple and mandrel tools;

a spiral screw connections; and

one or more hydraulic packers.

Nipple and mandrel tools, sometimes also defined as landing nipples and lock mandrels, are known in the art for securing and locking parts, in particular bore parts, within a pipeline or greater bore. Typical examples are available from Halliburton under their Otis (RTM) range. They can include locking keys, generally being retractable, and are used in installing in tubing strings. They may include one or more seals, and achieve positive location with minimum restriction, optionally with locking sleeves.

Spiral screw connections are also well known in the art, generally having one part with a male thread, and a second part or station with a female complementary threaded bore, which together can be spinal screwed together to locate and lock the submersible pump in the end fitting.

Hydraulic (operated) packers are also well known in the art of well completion to separate well production zones. These can be combined with the elements mentioned hereinabove to ensure that the pump is well secured, and that no or limited communication exists between the inlet and out of the pump.

Other apparatus or systems for locating and locking the submersible pump into an end fitting include ball-grab systems, externally operated screws or pins, claw mechanisms, mechanical packers and polymer systems (that can be activated using heat and/or chemicals).

The apparatus or system for locating and locking the submersible pump into the end fitting hold and maintain the submersible pump, optionally without any axial movement after installation.

The prior art methods of powering an electrical submersible pump in a pipeline use a separate or new power cable that is run along the inside of the pipeline, which must either be torque balanced or attached to another support, such as internal tubing, (i.e. the tubing using to support the ESP and transfer fluids therefrom along the pipeline). The need for a separate internal power cable still involves several failure modes, including possible internal damage, and limited tubing size. In the present invention, the submersible pump could be powered either through the flexible subsea hydrocarbon pipeline itself, or through one or more wall penetrators in the end fitting, thus maintaining the flexibility of the flexible subsea hydrocarbon pipeline and avoiding known prior art failure modes. Where the submersible pump is powered through the flexible subsea hydrocarbon pipeline itself, this can be by using one or more of power cables, gas lines and/or hydraulic lines or tubes provided as part of the flexible subsea hydrocarbon pipeline, either inherently, or one or more further added cables, lines or tubes added in the manufacturing of the flexible subsea hydrocarbon pipeline, and dedicated to powering a submersible pump.

For example, where the flexible subsea hydrocarbon pipeline is an Integrated Production Bundle, which includes one or more power cables or power lines, the submersible pump could be an electrical submersible pump, which can be connected to one or more of said power cables or power lines. In another example, where the flexible subsea hydrocarbon pipeline is an Integrated Production Bundle, which includes one or more tubes for gas lift, the submersible pump could be a gas powered submersible pump, which can be connected to one or more of gas tubes. The gas of the gas lift going down the IPB could also be used to power the pump, and once so-used, the gas could be released downstream of the pump to provide lift to hydrocarbons exiting the pump.

In this way, power for the submersible pump is conveniently part of the flexible subsea hydrocarbon pipeline itself, and can be attached as and when required in or within the end fitting using one or more electrical, gas or hydraulic connectors or connections. This avoids the need for a separate power cable to be extended along and within the core, i.e. the production core or bore of the flexible subsea

hydrocarbon pipeline from the power source, usually the sea level production vessel or platform.

Where the submersible pump is powered using one or more end fitting wall penetrators, such as selected from the group comprising: electrical penetrators, gas penetrators, and hydraulic penetrators, and combinations of same. The

penetrator(s) could be located axially, radially, or both, in or through a suitable part of the end fitting, and be powered by one or more external power cables, in a manner known in the art. This again avoids the need for a separate power cable to be extended along and within the core, i.e. the production core or bore of the flexible subsea hydrocarbon pipeline from the power source, usually the sea level production vessel or platform. The use, maintenance and replacement of external power cables are more controllable by the operator.

Wall penetrators may have a dry end and a wet end, and include various designs of plugs, caps, and receptacles, including 'ROV receptacles' which allow an ROV to connect an external electrical cable.

The present invention may include the use of one or more different types of penetrators, including an internal bore or core penetrator, tree cap penetrators, and known associated fittings including plugs, sockets, receptacles etc. used for subsea connector or connection systems. The electrical connection or connections required between the submersible pump and power supply can be any suitable apparatus, system or mechanism, such as but not limited to socket arrangements, screw connectors, etc. Other electrical connectors are known in the art, such as those provided by Zeitecs, in particular the Zeitecs Shuttle™ connector which exhibits plug and play connectivity.

Similarly, the connection or connections required between the submersible pump and any high pressure gas supply could be any suitable apparatus, system or mechanism, such as but not limited to socket arrangements, screw connectors, etc.

According to another embodiment of the present invention, the flexible subsea hydrocarbon pipeline assembly further comprises an IPB fitting around at least part of the end fitting and at least part of the pipeline.

The IPB fitting may have any suitable size, shape and design, and is generally able to provide a circumferential housing around at least part of the end fitting and at least part of the pipeline, optionally to provide a support or location for the or an electrical connection required to power the submersible pump.

In a particular embodiment of the present invention, the flexible subsea hydrocarbon pipeline is an Integrated Production Bundle, the flexible subsea hydrocarbon pipeline assembly further comprises a specific termination fitting around at least part of the end fitting and at least part of the Integrated Production Bundle, and the submersible pump is powered by one or more of power cables or gas lines extending from the Integrated Production Bundle and operable through the umbilical termination fitting and the end fitting.

In one embodiment, the IPB fitting comprises one or more circumferential housings, co-axially aligned with the pipeline and the end fitting, and having one or more chambers, optionally sealable chambers, through which one or more power connections can pass, optionally by the location of one or more passageways such as tubings or tubes able to carry a power connection. In another embodiment of the present invention, the IPB fitting includes one or more receptacles or sockets adapted to accept an external power connection, such as an external lead or jumper attachable by an ROV or the like. Suitable ROV wet mateable connectors are known in the art.

In another embodiment, the IPB fitting includes one or more internal tubes able to mate with one or more complementary passageways through the end fitting.

According to a third aspect of the present invention, there is provided a method of forming a flexible subsea hydrocarbon pipeline assembly as defined herein comprising at least the steps of:

(i) providing a submersible pump;

(ii) locating the submersible pump in the end fitting of the flexible subsea hydrocarbon pipeline;

(iii) locking the submersible pump into the end fitting: and

(iv) connecting the submersible pump to a power source.

In the method of the present invention, the submersible pump is optionally an electrical submersible pump, and the power source is one or more power cables.

Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying schematic drawings in which: Figure 1 is a perspective view showing the structure of a prior art flexible subsea hydrocarbon pipeline;

Figure 2 is a perspective view showing the structure of a prior art Integrated

Production Bundle (IPB);

Figure 3 is a side cross sectional view of the flexible subsea hydrocarbon pipeline of Figure 1 having an end fitting according to one embodiment of the present invention; Figure 4 is a side cross sectional view of another embodiment of the present invention comprising Figure 3 and an electrical submersible pump located and locked in the end fitting; Figure 5 is a side view of another embodiment of the present invention using a IPB and end fitting, with an electrical submersible pump located in the end fitting and powered by power cable from the IPB; and

Figure 6 is a schematic view of an embodiment of the present invention using a plurality of flexible subsea hydrocarbon pipeline assemblies between a floating vessel and a seabed.

Referring to the drawings, Figure 1 shows a typical flexible subsea hydrocarbon pipeline production structure 10, comprising a series of concentric and modular layers, being a first or inner or central spiralled carcass 1 1 , such as formed in stainless steel, and which is wholly of substantially hydrocarbon resistant. This is followed by a pressure resistant polymeric layer (e.g. polyamide layer 12), a single metallic layer resistant to hoop stress or pressure vault layer 13, a double layer of cross armouring 14, such as helically wound steel wires, followed by an outer or external sheath 15, generally formed of a polymer or suitable plastic. The flexible pipeline structure 10 can include one or more polymeric or metallic other layers, in particular reinforcement layers, but requires maintaining its flexibility and dynamic behaviour known in the art. Figure 2 shows an exploded view of the end of an Integrated Production Bundle (IPB) 20. The core of an IPB can be same or similar to that of the subsea hydrocarbon pipeline production structure 10 shown in Figure 1 , i.e. comprising a series of concentric and modular layers with a final plastic sheath 22. Around the sheath 22 are located a series of tubes or cables 24, which can also be helically wound or added in an SZ manner, with plastic spacers 28 thereinbetween to support and hold the location of the tubes or cables 24: all of which can then be surrounded by one or more further thermal insulation and/or protection layers or sheaths, such as the final layer 30 shown in Figure 2. IPBs are known in the art, and in particular, IPBs allow the integration of a production bore, such as the production structure 10 shown in Figure 1 , along with other tubes and lines, such as for gas lift and umbilical functionality, including power, electrical and fibre optic lines, signal cables, and the like, all provided in an integral form in multi-bore pipeline. Figure 3 shows a cross sectional view of a schematic flexible subsea hydrocarbon pipeline 31 , which can be any suitable pipeline including the basic production structure 10 shown in Figure 1 , or the IPB 20 shown in Figure 2, etc., attached to an end fitting 32. The end fitting 32 generally has a first end 33 mateable with the flexible subsea hydrocarbon pipeline 30, and a second or opposite end 34 having a flanged head portion 35, including a plurality of aligned bolt holes 36, though which suitable bolts (not shown) could be used to attach the flanged head 35 to a well production head or manifold etc. (not shown) on or near a seabed, in a manner known in the art. The end fitting 32 includes a central bore 38 intended for the passage of hydrocarbons from a well head (or manifold or intermediate structure, etc.) generally located on or near a seabed, into the pipeline 30 for passage to sea level, such as to a floating production vessel.

The end fitting 32 may be adapted to wholly or partly house a separable submersible pump (not shown) into the central bore 38, using the steps of providing the pump

(either simultaneously with or after manufacture of the pipeline), locating and locking the pump into the end fitting, and connecting the pump to a power source (not shown). Thus, Figure 3 shows an example of a flexible subsea hydrocarbon pipeline of the present invention comprising a flexible subsea hydrocarbon pipeline 31 and end fitting 32 adapted to wholly or partly house a separable submersible pump.

Figure 6 shows a typical arrangement for a flexible subsea hydrocarbon pipeline 46 between a seabed 40 and a floating production vessel 44 at sea level 42. Figure 6 is discussed in more detail hereinafter.

Figure 4 shows a first embodiment of the present invention, comprising a flexible subsea hydrocarbon pipeline assembly 50 comprising a flexible subsea hydrocarbon pipeline 52, having an end fitting 54, and an electrical submersible pump 56 partly located and locked in the end fitting 54.

In more detail, the flexible subsea hydrocarbon pipeline 52 shown in Figure 4 may be the same as or different to the flexible pipeline production structure 10 shown in Figure 1 , and may extend some metres, hundreds of metres, or even thousands of metres to a floating production vessel of the like. The flexible pipeline 52 is mated to one end of the end fitting 54 using any suitable mechanism inside cover 53, as known in the art.

The electrical submersible pump (ESP) 56 shown in Figure 4 comprises an electrical penetrator 58, a motor 60, a pump 62, a landing nipple 64 and a locking mandrel 66. One end of the pump 62 is connected to the motor 60, and the another end 68 is connected to tubing 70 passing up the flexible pipeline 52.

The electrical penetrator 58 is connected to an electrical dock 72 located on the inner surface of the end fitting 54, and designed to provide the drive to the motor 60. The electrical dock 72 is connected via an external electrical connection 74 which passes through a wall of the end fitting 54.

The ESP 56 partly extends into the flexible pipeline 52, and is located and locked into the end fitting 54 by use of a landing nipple 64 which is similar to that used in the oil and gas completions industry, and which can be integrated into the internal surface of the end fitting 54. This machined internal surface of the end fitting 54 provides a seal area and a locking profile. The casing of the ESP 56 meanwhile incorporates a locking mandrel 66 (also used in the completions industry) to lock the ESP 56 in place in the end fitting 54.

In use, fluids such as hydrocarbons enter the end fitting 54 through the end opening 76, past an electrical dock 72 located within the end fitting 54, past motor 60, and into the pump 62 which increases its pressure for passage subsequently up the flexible pipeline 52.

An advantage of the present invention is that the flexible pipeline 52 and end fitting 54 can be provided without the ESP 56, which can be added thereafter when additional in line pressure is required.

Figure 4 shows the end fitting 54 having an external electrical connection 74. This may have one end attached to or being a suitable electrical connector 82 that is accessible externally from the end fitting 54, such as by a ROV receptacle arm, and a tree cap penetrator 80 at least partly housed in the wall of the end fitting 54. The tree cap penetrator 80 can connect to an internal penetrator 78, said penetrator 78 having its opposite end penetrating into the electrical dock 72. Such electrical arrangements and connectors are well known in the art, and include those available under the brand SpecTRON available from Siemens Subsea in the UK and elsewhere. An external connection with a suitable power cable can be provided using an ROV or the like.

Figure 5 shows a second flexible subsea hydrocarbon pipeline assembly 100 according to another embodiment of the present invention. Figure 5 shows a flexible subsea hydrocarbon pipeline 102 having an end fitting 104, and an electrical submersible pump (ESP) 106 partly located and locked in the end fitting 104.

The flexible subsea hydrocarbon pipeline 102 is an IPB, such as that shown in Figure 2, and having a central core 108 optionally being the same or similar to that shown in Figure 1 , and a series of outer gas tubes 1 10 and/or power cables 1 12 bundled around the core 108, to provide known end of pipeline ancillary functionality and provisions, such as power cables, fibre optics, signal cables and the like.

The second flexible subsea hydrocarbon pipeline assembly 100 includes an IPB fitting 120 extending from the end fitting 104 to a sealing assembly 121 at the end of the outer part of the IPB pipeline 102.

The IPB fitting 120 comprises a co-axial series of shells able to form two longitudinal chambers 122, 124. In the first chamber 122, Figure 5 shows one of the power cables 1 12 extending from the IPB pipeline 102 into a tubing 126 that passes through a first radial wall 128 into the second chamber 124. In the second chamber 124 is a second tubing 130 able to provide a passageway to a passageway 132 in the end fitting 104. Within the bore 134 of the end fitting 104, there is located an internal penetrator 136 able to connect with a docking station 138 which then connects with the motor 140 and pump 142 at one end of the electrical submersible pump 106 in a manner shown in Figure 4.

In Figure 5, it is shown that electrical power can be provided to the electrical submersible pump 106 by electrical connection from the power cable 1 12 through the first and second chambers 122, 124 and radial wall 128 of the IPB fitting 120, and through the end fitting 104 to reach the internal penetrator 136, etc. In an alternative embodiment, gas power can be provided to a suitable gas powered submersible pump in the end fitting 104 from or by one or more of the gas tubes 1 10 at the end of the IPB pipeline 102. The gas power can be routed to the end fitting 104 through the first and second chambers 122, 124 and the radial wall 128 of the IPB fitting 120 (partly shown in Figure 5), in the same way as electrical power from power cable 1 12. Hydraulic power can be similarly provided to power a suitable submersible pump from the IPB pipeline 102. Figure 5 shows examples of how power to the submersible pump can be provided by an internal connection from the end of the pipeline to the end fitting, (and then, through the end fitting to the submersible pump). The IPB fitting 120 provides a suitable and optionally sealed housing around the end of the pipeline 102 and the end fitting 104, which can safely house the required electrical, gas etc. connection all the way to the end fitting without any external connection required. As such, the arrangement shown in Figure 5 forms an integral termination assembly for a flexible subsea hydrocarbon pipeline, within which, either integrally or added separately, a submersible pump can be located and operated. Figure 6 shows a schematic view of a flexible pipeline 46 extending between a seabed 40 and a floating production vessel 44 on a sea level 42. Figure 6 shows the possibility of using three separate flexible pipelines 48a, 48b and 48c, each having complimentary end fittings 49 between which are located electrical submersible pumps 43 in mid-line arrangements, such that the overall pipeline 46 has two sets of pressure increasing stations along its length, to assist and boost flow of

hydrocarbons from a seabed installation (not shown) to the floating production vessel 44. It is clear to the skilled man that the present invention can provide any number of submersible pumps along an overall flexible pipeline, by introducing any number of mid-line arrangements as shown in figure 6.

Whilst the use of submersible pumps are known in the art for boosting the pressure and flow in a producing well, the present invention provides dramatic increase in flexibility of the use of submersible pumps, and in particular with use of flexible hydrocarbon pipelines. Submersible pumps can now be added at short notice and retrospectively into suitable end fittings, to allow an operator to improve oil recovery generally at the end of a production fuel life, or should a drop in production happen. That is, subsea boosting is possible in existing flexible pipelines by the addition of submersible pumps using the present invention. Further, 'plug and play' can be used so that where a flexible pipeline is supplied with a 'plug in ready' ESP, then it is a simple matter to install a submersible pumps with minimal change to the system.

Thus, a well or field producer can select options required, particularly for

emergencies or sudden pressure drops, or for long term assistance where 'end of field' can be seen possible and the well pressure is decreasing, without increased up front costs in increasing the pressure required to bring the hydrocarbons to sea level.

In particular, for complex and difficult fields to be developed, the use of an IPB may already be involved for flow-assurance reasons. The electrical cables or gas lines or hydraulic tubes required to power a submersible pump can be available and used 'on-demand'. This reduces the need for laying a separate gas line, or the use on internal tubing to power the submersible pump.

The present invention is possible with relatively minor changes to the manufacture of known or 'standard' end fittings and flexible subsea hydrocarbon pipelines, with the ability to machine in an electrical or gas fitting, install landing nipples and replace certain armour wires with electrical cables (if full IPB functionality is not required). This means the operator can purchase this option as a contingency, or as an option to use in the future without increased upfront cost. Furthermore, fitting a submersible pump in the end fitting allows for fitting a larger diameter pump, and as the end-fitting is made of steel, the heat generated from the pump operation can be discharged to the environment without the possible adverse effect that could be brought to a flexible pipe should the pump be located inside the pipe itself.