PUMP SYSTEM, METHOD AND USES FOR TRANSPORTING INJECTION WATER TO AN UNDERWATER INJECTION WELL

Abstract

Pump system (2), method and use for transporting injection water (10) to an underwater injection well (12), wherein the pump system (2) comprises a pressure-tight enclosure (14) located underwater and containing: —a pump arrangement (18) for pumping the injection water (10); —a drive arrangement (20) connected to the pump arrangement (18) for operation of the latter; —a cooling arrangement (46) for removing heat from the interior of the enclosure (14); and —at least one control unit (48) for operating control of at least said drive arrangement (20); wherein the enclosure (14) also comprises: —an inlet (24), which is flow-connected to an upstream side of the pump arrangement (18); and —an outlet (28), which is flow-connected to a downstream side of the pump arrangement (18). The characteristic of the pump system (2) is that the inlet (24) of the enclosure (14) is flow-connected to a body of water (4) in which the enclosure (14) is located, water from this body of water (4) being used as injection water (10) to said underwater injection well (12); and —the outlet (28) of the enclosure (14) is flow-connected to the injection well (12).

Description

FIELD OF THE INVENTION

The invention relates to a pump system and a method for transporting injection water to an underwater injection well. The invention also relates to the use of the pump system and to the use of said method.

BACKGROUND OF THE INVENTION

A relatively common method for increasing the degree of extraction of hydrocarbons from an undersea reservoir is to pump water into the reservoir via an underwater injection well, so-called secondary extraction.

The most common method has been and still is to undertake such offshore water injection from a surface installation, for example from a moored platform or from a floating installation, such a floating installation consisting of a floating platform or a ship. On such a surface installation, injection pumps and various other injection-related equipment will usually be located above water. Use can thereby be made of so far well-known, well-tried and effectively functioning surface equipment, including known injection pumps and their drive arrangements, for such injection purposes. The major disadvantage with water injection from such a surface installation, however, is the scope, complexity and the associated costs of constructing and installing the surface installation offshore. Such surface installations are therefore largely used in connection with hydrocarbon extraction from large oil fields.

As underwater completion and underwater production have become more common, it has also become more common to inject water by means of underwater equipment located on or near a seabed, for example on the bottom of an ocean or lake. In this context, the injection water may also be subjected to various treatment underwater, for example filtering and/or chemical treatment, by means of associated equipment located on or near the seabed. The use of such underwater equipment is typically undertaken in connection with secondary extraction from smaller and/or complex oil fields, and/or in secondary extraction at greater water depths than is usual for surface installations. In the case of underwater completion, the well head of the injection well is located on the seabed, and said underwater equipment is flow-connected to the well head. This underwater equipment comprises at least an underwater injection pump, which will typically be specially adapted for operation underwater at the relevant water depth. For this reason, such an underwater injection pump will typically be of a design which, technically speaking, is substantially more complex, more extensive and more robust, and thereby substantially more costly than a corresponding well-known, well-tried and effectively functioning surface pump. In addition, such an underwater injection pump is often exposed to very demanding and harsh operating conditions underwater. Such operating conditions often reduce the operating reliability and service life of the underwater pump. This may therefore lead to shorter maintenance intervals and thereby more frequent intervention operations, and increased operating costs associated with operation of the underwater pump. In the worst case, such operating conditions and associated disadvantages may render seabed-based water injection into an injection well impossible.

It is thus desirable to avoid the use of such specially adapted, costly and sometimes unreliable underwater injection pumps for injecting water into an underwater-completed injection well. It is desirable to make the water injection more cost effective and reduce service intervals.

STATE OF THE ART

US 2008/0190291 A1 describes, in the form of a method and an apparatus, a submersible processing environment for diverse underwater processing of a hydrocarbon stream that is produced from an underwater well.

The submersible processing environment according to US 2008/0190291 A1, is used for the processing of a hydrocarbon stream from an underwater well.

In view of the prior art, there is a need to provide more cost efficient and reliable water injection equipment. There is a further need to provide a technical solution in which such equipment can be arranged on a deck of a floating vessel, and then be submerged in a body of water through a working aperture (“moon pool”) in the deck of the vessel. It is also desirable, at a later date, to retrieve the equipment via such a working aperture in the deck of the vessel, for example for maintenance and/or repair of the equipment, possibly for the replacement of various components etc.

SUMMARY

It is an object of the invention to remedy or to reduce at least one disadvantage of the state of the art, or at least to provide a useful alternative to the state of the art.

This object is achieved by the features of the independent claims. The dependent claims describe embodiments of the invention.

According to a first aspect of the invention, a pump system is provided for transporting injection water to an underwater injection well, wherein the pump system comprises a pressure-tight enclosure located underwater and containing:

• • a pump arrangement for pumping the injection water;
  • a drive arrangement connected to the pump arrangement for operation of the latter;
  • a cooling arrangement for removing heat from the interior of the enclosure; and
  • at least one control unit for operating control of at least said drive arrangement;
    wherein the enclosure also comprises:
  • an inlet which is flow-connected to an upstream side of the pump arrangement; and
  • an outlet which is flow-connected to a downstream side of the pump arrangement. In the pump system, the inlet of the enclosure is flow-connected to a body of water in which the enclosure is located, water from this body of water being used as injection water to said underwater injection well; and
  • the outlet of the enclosure is flow-connected to the injection well.

Using such a submerged pump system, it is possible for so far well-known, well-tried, effectively functioning and reliable surface pumps, and drive arrangements for these, to be located underwater in said body of water. Untreated water can then be drawn in more or less directly from the surrounding body of water, to be then pumped onwards down into the underwater-completed injection well. This avoids having to use specially adapted, costly and complicated underwater equipment for such water injection purposes.

The pump system in question might therefore represent a substantial technical contribution in being able to undertake economically viable, secondary extraction from smaller and/or complex oil fields, and from oil fields at greater water depths than is usual for surface installations.

In an embodiment, at least one control unit of the pump system may comprise various electronic components, including electronic circuit boards, programs, transmitter units, receiver units, circuit breakers, couplings, power connections and the like, for controlling and possibly monitoring the operation of the pump system when installed in its position of use underwater. The scope of the components in the control unit is determined by the actual design of the pump system. The control unit may therefore at least comprise components/equipment enabling it to communicate signals with said drive arrangement, and possibly also with said cooling arrangement and/or other equipment in the pump system.

The pump system may also comprise various coupling equipment, for example valves, couplings, flanges, packings, connecting lines and hoses, for connecting various components which are included in or which are associated with the pressure-tight enclosure.

The pump system may furthermore comprise various regulating equipment for regulating and thereby controlling the operation of various components in the pump system.

In addition, the pump system may be designed for connection to various auxiliary equipment, which among other things is used to carry out servicing operations on the pump system, or on equipment which is associated with the pump system, possibly for coupling various equipment to the pump system. Such auxiliary equipment may therefore include ROV-based equipment, where an unmanned and remotely controlled underwater vessel (“ROV”) carries out the relevant servicing operations by means of remote control from a host vessel on the surface. In the latter case the equipment in question, which is connected to the pump system, must also be designed for interaction with the ROV-based equipment.

Said enclosure in the pump system may advantageously be located on or near the bottom of a body of water, for example on a seabed or on the bed of a lake, river or delta. In this context, the enclosure may possibly be located on a suitable foundation.

Furthermore, the pump arrangement in the enclosure may comprise or consist of any suitable pump arrangement, for example a centrifugal pump. In addition, the drive arrangement of the pump arrangement may comprise or consist of any suitable drive arrangement, for example an electric motor or a hydraulic motor.

The pressure-tight enclosure of the pump system may also contain a lubrication arrangement for lubricating at least one moving part in the pump arrangement or the drive arrangement.

In addition or alternatively, if the pump arrangement and/or the drive arrangement comprise rotating parts, the pump arrangement and/or the drive arrangement may be provided with magnetic bearings for the operating support of at least one rotating part in the pump arrangement and/or in the drive arrangement. In this context, the magnetic bearings may be connected to at least one control unit for operating control of the bearings. The magnetic bearings may also be connected to at least one source (e.g. electric power source) for supplying drive power to the bearings.

The pressure-tight enclosure may also contain monitoring equipment for operational monitoring of at least said pump arrangement, drive arrangement and cooling arrangement. In this context, the monitoring equipment is connected to at least one said control unit for operating control of the monitoring equipment and the transmission of monitoring data to a remote host device. The monitoring equipment is also connected to at least one source (e.g. electric power source) for supplying drive power to the monitoring equipment.

Furthermore, the pressure-tight enclosure may contain a gas, for example air, at atmospheric or virtually atmospheric pressure, that is to say an internal pressure of approximately 1 atmosphere. The pressure inside the enclosure may for example lie within a range of about 1 to about 2 bar. This assumes that the enclosure is designed to be capable of withstanding pressure differences between the water pressure that prevails outside the enclosure at the water depth in question, and the atmospheric or virtually atmospheric pressure inside the enclosure. Set to such an internal gas pressure, the enclosure can be raised to the surface and opened for servicing, modification or the like, without dangerous situations arising as a result of a pressure difference between the interior of the enclosure and the surrounding atmospheric pressure at the surface. If desired or necessary, the gas in the enclosure may also consist of an inert gas, for example nitrogen or argon. This may provide improved electric isolation and/or reduce corrosion.

In addition, the enclosure may be connected via a cabled connection to a remote host device for transferring contaminated gas from the enclosure and for returning uncontaminated gas to the enclosure. Such a solution may be appropriate, for example, if it is desirable to remove water vapor from the injection water and/or vapor for a coolant and/or a fluid lubricant, for example oil vapor, from the interior of the enclosure. The contaminated gas can thereby be transported from the enclosure and to the host device, where the contaminated gas is either cleaned or replaced. The uncontaminated gas may then be returned to the enclosure via the cabled connection.

In addition, equipment, modules and units that are to be located underwater offshore can often be large, heavy and bulky, possibly with a relatively large lateral extent. For this reason, it may be difficult to locate such equipment on a deck of a floating vessel, for example a boat, for transport from the shore to the relevant location offshore. If the vessel is also provided with a working aperture (“moon pool”) in the deck of the vessel, it may also be difficult to lower such equipment down through the working aperture in the deck, and possibly also to retrieve the equipment though this working aperture. In some cases, therefore, bulky equipment must be transported suspended under or behind the vessel during transport offshore.

Such transport of awkward equipment is shown, for example, in the publication WO 03/074353 A1, which corresponds to NO 316168 B1, and in publication WO 2009/070034 A2. Alternatively, such equipment may be located on a deck of a large transport vessel, for example a lighter, and transported to the relevant location offshore. The equipment is then hoisted over the side of the vessel and lowered down into the water. Such a working operation may also be awkward with an associated uncertainty and risk.

Since the enclosure in the pump system in question may also be large, heavy and bulky, the pump arrangement and drive arrangement of the enclosure may advantageously be vertically aligned in relation to one another. Furthermore, the enclosure may be designed with an outer perimeter or circumference that fits inside or is specially adapted to such a working aperture in a deck of a floating vessel. In this context, and by means of suitable aids, the vessel is designed to be capable of lowering the enclosure down into the water, and where necessary retrieving the enclosure from the water through the working aperture in the deck of the vessel. It is thereby possible to transport the enclosure and its contents on the deck of the vessel when shipping the enclosure out to the relevant location offshore, following which the enclosure is lowered down into the water via said working aperture in the deck of the vessel.

Aligning the pump arrangement and its drive arrangement vertically in relation to one another affords a relatively narrow enclosure, which fits both on the deck of the vessel and inside the working aperture in the deck. For this reason the enclosure can advantageously have a height that is greater than the largest horizontal transverse dimension of the enclosure. The enclosure may for example comprise or consist of a vertically upright, cylindrical container of a height that is greater than the diameter of the container. In this context, the pump arrangement can be arranged vertically beneath the drive arrangement, or the pump arrangement can be arranged vertically above the drive arrangement.

In one embodiment, said control unit may comprise at least one remotely controlled control unit, which, via a cabled connection, is connected to a remote host device for transmitting at least control signals to the control unit. Such a cabled connection may consist, for example, of a control cable (“umbilical line”).

Alternatively or in addition, the enclosure may be connected via a cabled connection to a remote host device for transmitting drive power to powered equipment in the pump system. Such a cabled connection may consist, for example, of a suitable power transmission cable.

In another embodiment, the enclosure may be connected via a cabled connection to a remote host device for transmitting both control signals to the control unit and drive power to powered equipment in the pump system.

In addition, said control system may also comprise at least one remotely controlled backup control unit, which is connected via a wireless connection to a remote host device for transmitting at least control signals to the control unit. In this context, the backup control unit is connected to a transceiver for wireless communication with the remote host device. The wireless connection may consist, for example, of an acoustic connection or a radio frequency connection. Alternatively or in addition, the enclosure may be provided with a power supply for operation of the remotely controlled backup control unit. Said power supply may consist, for example, of at least one battery.

Furthermore, the cooling arrangement of the enclosure may comprise at least one closed flow circuit, for example a pipe loop, containing a coolant, where the closed flow circuit is connected to the internal atmosphere of the enclosure for absorbing heat therefrom, and where the closed flow circuit comprises a heat exchanger, which is connected to said body of water on the outside of the enclosure for removing heat transmitted from the internal atmosphere of the enclosure by way of the coolant of the flow circuit. This cooling arrangement also comprises a means of delivery for the coolant, for example a suitable pump. The heat exchanger may advantageously be arranged on the outside of the enclosure and may therefore be in direct contact with the cooling body of water. Alternatively, the heat exchanger may be arranged inside the enclosure and may comprise an open flow circuit, which via at least one liquid-tight bushing through the wall of the enclosure is in direct contact with the cooling body of water outside the enclosure.

Alternatively, the cooling arrangement of the enclosure may comprise an open flow circuit, for example a pipe connection/hose connection, including a control cable (“umbilical line”), containing a coolant, where the open flow circuit is connected to the internal atmosphere of the enclosure for absorbing heat therefrom, and where the open flow circuit is connected to a remote host device for at least the circulation and possibly also the replenishing of coolant, and for removing heat transmitted from the internal atmosphere of the enclosure by means of the coolant of the flow circuit.

Furthermore, the lubrication arrangement of the enclosure may comprise at least one closed flow circuit, for example a pipe loop, containing a fluid lubricant, where the closed flow circuit is connected to lubricated equipment in the pump system. This lubrication arrangement also comprises a means of delivery for the fluid lubricant, for example a suitable pump.

Alternatively, the lubrication arrangement of the enclosure may comprise an open flow circuit, for example a pipe connection/hose connection, including a control cable (“umbilical line”), containing a fluid lubricant, where the open flow circuit is connected to lubricated equipment in the pump system, and where the open flow circuit is connected to a remote host device for at least the circulation and possibly also the replenishing of fluid lubricant, and for lubricating the lubricated equipment in the pump system.

For transmitting at least control signals to the control unit, said control unit may be connected to at least one wet-mateable plug connection arranged in the wall of the enclosure and designed for coupling to a separate, cabled connection.

Alternatively or in addition, and for transmitting drive power to the powered equipment in the pump system, the wall of the enclosure may be provided with at least one wet-mateable plug connection designed for coupling to a separate, cabled connection.

As a further alternative or in addition, and for transmitting both control signals to the control unit and drive power to powered equipment in the pump system, the wall of the enclosure may be provided with at least one wet-mateable plug connection designed for coupling to a separate, cabled connection.

All of these plug connections may for example comprise or consist of a plug and a socket, which afford a mating fit when coupled together.

By means of such a wet-mateable plug connection, a cabled connection, for example a control cable and/or a power transmission cable, can be easily coupled to or uncoupled from the enclosure by means, for example, of a remotely controlled underwater vessel (“ROV”).

Said remote host device, moreover, may comprise or consist of a surface installation on land or offshore. On land the surface installation may comprise, for example, of a building or the like, in which an operator of the pump system is situated. Offshore the surface installation may comprise or consist of an anchored platform or a floating installation, for example a floating platform or a suitable vessel/ship.

The inlet of the enclosure may furthermore be designed to be closeable, for example by means of a suitable valve arrangement.

Alternatively or in addition, the outlet of the enclosure may be designed to be closeable, for example by means of a suitable valve arrangement. In one embodiment the outlet of the enclosure may be connected to the injection well via an underwater line, for example a pipeline. In another embodiment, the outlet of the enclosure may be directly connected to the injection well, for example the outlet is connected to a well head for the injection well.

In addition, the enclosure may be flow-connected to at least one underwater installation for treatment of the injection water, where said underwater installation is located underwater in said body of water. The enclosure can therefore be connected to said underwater installation via an underwater line, for example a pipeline.

Said underwater installation may comprise at least one arrangement for removing solid particles from the injection water without filtering. In this context it is most advantageous if the inlet of the enclosure is connected to one or more such arrangements. At least some solid particles will thereby be removed from the injection water before this reaches the enclosure and its pump arrangement. An example of such an underwater arrangement is described in WO 2007/035106 A1, which is incorporated herein by reference in its entirety. This underwater arrangement comprises a closed chamber, which is designed to allow the feed water to be fed directly into a lower part of the closed chamber, and which is also designed to allow the treated water to be fed out of an upper part of the closed chamber. This closed chamber also has a cross sectional area which is designed to allow the water to flow from the lower part to the upper part with a rate of flow that is low enough for the unwanted solid particles to be precipitated out of the water under gravity. The closed chamber may furthermore be designed as a container or module that is located on a seabed or the like, for example.

Alternatively or in addition, said underwater installation may comprise at least one arrangement for chemical treatment of the injection water. In this context, at least one inlet and outlet of the enclosure may be flow-connected to one or more such arrangements for chemical treatment of the injection water. An example of such a chemical treatment arrangement is described in WO 2004/090284 A1, which is incorporated herein by reference in its entirety. This patent publication relates to a method and an apparatus for undersea chemical treatment of injection water, using a modular underwater apparatus that is connected to an injection well for injection of the water. The apparatus comprises at least one container, which is provided with at least one type of water-soluble solid chemical. The container can be changed, for example, by means of a remotely controlled underwater vessel (“ROV”). The water is then brought into contact with the solid chemical, in such a way that it is gradually dissolved and mixed with the water. The ready-treated water is then injected into a reservoir connected to the well. Chemical treatment and water injection can thereby be undertaken without having to use a directly superjacent surface installation or vessel. The water-soluble solid chemical may comprise chlorine and/or biocide, but also various other chemicals, such as said oxygen-removal agents, corrosion inhibitors and settlement inhibitors. This chemical treatment arrangement may consist of a separate unit or it may be incorporated into the aforesaid underwater arrangement for the removal of unwanted solid particles from the feed water without filtering.

As a further alternative or in addition, said underwater installation may comprise at least one arrangement for the destruction of organic material in the injection water. In this context also, at least one inlet and outlet of the enclosure may be flow-connected to one or more such arrangements for the destruction of organic material in the injection water. An example of such a destructive arrangement is described in WO 2007/073198 A1, which is incorporated herein by reference in its entirety. This patent publication relates to a method and an arrangement for destroying organic material in injection water for an injection well. The arrangement uses at least one electrochemical cell with associated operating means for the in situ electrolytic production from water of at least short-lived, free hydroxyl radicals. With the aid of the operating means, the electrochemical cell is designed to be capable of ducting the injection water through it as basic material for the in situ production of at least said free hydroxyl radicals from the injection water. Such free hydroxyl radicals will immediately destroy organic material with which they come into contact in the injection water. This destructive arrangement may consist of a separate unit or it may be incorporated into the aforesaid underwater arrangement for the removal of unwanted solid particles from the feed water without filtering. As a further alternative, the destructive arrangement may be combined with the aforementioned chemical treatment arrangement.

At least said one underwater installation for treatment of the injection water may, like the enclosure, advantageously be located on or near the bottom of a body of water, for example on a seabed or on the bed of a lake, river or delta. In this context, the underwater installation may, if necessary, be located on a suitable foundation.

According to a second aspect of the invention, a method is provided for transporting injection water to an underwater injection well, where the method uses a pump system comprising a pressure-tight enclosure which contains:

• • a pump arrangement for pumping the injection water;
  • a drive arrangement connected to the pump arrangement for operation of the latter;
  • a cooling arrangement for removing heat from the interior of the enclosure; and
  • at least one control unit for operating control of at least said drive arrangement;
    where the enclosure also comprises:
  • an inlet which is flow-connected to an upstream side of the pump arrangement; and
  • an outlet which is flow-connected to a downstream side of the pump arrangement;
    where the method comprises the following steps:

(A) lowering the pressure-tight enclosure down into the water and locating the enclosure underwater.

The characteristic of the method is that it also comprises the following steps:

(B) flow-connecting the inlet of the enclosure to a body of water in which the enclosure is located, water from this body of water being used as injection water to said underwater injection well;

(C) flow-connecting the outlet of the enclosure to the injection well; and

(D) starting said drive arrangement and thereby the pump arrangement in order thus to pump the injection water onwards to the injection well.

The same comments as were made in connection with the preceding description of the pump system according to the first aspect of the invention also apply to the method in question according to this second aspect of the invention.

In the embodiments, method may also comprise the following steps:

• • aligning the pump arrangement and the drive arrangement vertically in relation to one another;
  • designing the enclosure with an outer perimeter (circumference) that fits inside a working aperture (“moon pool”) in a deck of a floating vessel; and
  • lowering the enclosure down into the water via the working aperture in the deck of the vessel.

The enclosure and its contents, which may be large, heavy and bulky, can thereby be transported on the deck of a vessel when shipping the enclosure out to a location offshore, following which the enclosure is lowered down into the water via a working aperture (“moon pool”) in the deck of the vessel. At a later date the enclosure can thereby be retrieved from the water via this working aperture. Aligning the pump arrangement and its drive arrangement vertically in relation to one another affords a relatively narrow enclosure, which fits both on the deck of the vessel and inside the working aperture in the deck. This obviates the need, for example, to transport such an enclosure with contents suspended beneath or behind the vessel when it is transported offshore, and possibly hoisting the equipment over the side of a vessel before lowering the equipment down into the water.

Furthermore, the method may also comprise the following steps:

• • locating at least one underwater installation for treatment of the injection water underwater in said body of water; and
  • flow-connecting the enclosure to said underwater installation for treatment of the injection water.

As stated in connection with the first aspect of the invention, said underwater installation may comprise at least one of the following types of underwater installations:

• • an arrangement for removing solid particles from the injection water without filtering, as described, for example, in WO 2007/035106 A1;
  • an arrangement for chemical treatment of the injection water, as described, for example, in WO 2004/090284 A1; and
  • an arrangement for the destruction of organic material in the injection water, as described, for example, in WO 2007/073198 A1.

According to a third aspect of the invention, the use of a pump system according to the first aspect of the invention is for transporting injection water to an underwater injection well.

According to a fourth aspect of the invention, the use of a method according to the second aspect of the invention is for transporting injection water to an underwater injection well.

The features of the embodiments described above and further below can be combined with each other unless noted to the contrary. Any of the described configurations of the pump system may be employed within the method of the second aspect of the invention, and the pump system may be configured so as to be capable of being employed or of implementing any of the method steps described above and further below.

BRIEF DESCRIPTION OF DRAWINGS

Some non-limiting examples of embodiments according to the invention are described below with reference to the accompanying drawing, in which

FIG. 1 shows a highly schematic vertical plan view, partly in section, of a pump system according to an embodiment of the invention, comprising, among other things, a pressure-tight enclosure, which contains a pump arrangement, etc., where the enclosure is located underwater on a seabed, and the enclosure is flow-connected to, among other things, a remote underwater injection well;

FIG. 2, also highly schematic and to a smaller scale, shows a first embodiment of a pump system in question, comprising the enclosure according to FIG. 1, where the upstream side of the enclosure is flow-connected to an underwater installation for treatment of the injection water that is drawn directly from the sea which surrounds the enclosure and the underwater installation, and where both the enclosure and the underwater installation are each connected to a remote and floating platform offshore for transmitting various signals, including control signals and monitoring data, and drive power to powered equipment in the enclosure and the underwater installation; and

FIG. 3, also highly schematic, shows a second embodiment of a pump system in question and the underwater installation according to FIG. 2, where, however, both the enclosure and the underwater installation are each connected to a remote location offshore or on land for transmitting said signals and drive power to the enclosure and the underwater installation.

The figures, as stated, are highly schematic and show only parts and equipment for the purpose of a better understanding of the invention. Furthermore, the figures are highly distorted with regard to the relative dimensions of parts and components shown in the figures i.e. the objects are not to scale with each other. In addition, the figures are highly simplified with regard to the shape and amount of detail of such parts and components. Identical, equivalent or corresponding parts in the figures have largely been quoted below with the same reference numerals.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a pump system 2 according to an embodiment of the invention located in a body of water in the form of seawater 4, where the pump system 2 is situated on a seabed 6 beneath a sea surface 8 (shown only in FIGS. 2 and 3). The pump system is designed for transporting injection water 10 to a remote injection well 12 on the seabed 6 (see FIGS. 2 and 3). In this context, seawater 4 is used as untreated water for the injection water 10 to the injection well 12.

The injection water can consist of water/untreated water that is drawn from a body of water in which the pump system in question is located when the system is in its position of use underwater. This body of water may consist of salt seawater, for example, or, when installed at a different location, of water from a lake, river, spring or groundwater deposit.

The pump system in question can furthermore be controlled and possibly monitored from a remote host device via one or more cabled and/or wireless communications connections. The pump system may also be supplied with power from a remote host device via at least one cabled power transmission connection. Such a host device may include a surface installation on land or offshore. Alternatively or in addition, the pump system in question may be linked to one or more underwater installations for various treatment of the injection water, for example filtering and/or various chemical treatment of the injection water.

The pump system 2 comprises a pressure-tight enclosure 14, which is located on a foundation 16 on the seabed 6. In this embodiment, the enclosure 14 consists of a vertically upright, cylindrical container of a height which is greater than the diameter of the container. The enclosure 14 contains an inert gas 17, for example nitrogen or argon, which is set to an atmospheric or virtually atmospheric pressure. The enclosure 14 also contains a pump arrangement for pumping the injection water 10, and a drive arrangement connected to the pump arrangement for operating the latter. In this embodiment, the pump arrangement is of a centrifugal pump 18, whilst the drive arrangement comprises an electric motor 20, which is rotatably connected to the centrifugal pump 18 via a rotatable shaft 22. In this connection, the centrifugal pump 18 and the electric motor 20 are vertically aligned in relation to one another, and the centrifugal pump 18 is arranged vertically below the electric motor 20.

The enclosure 14 further comprises an inlet in the form of an external, first flange coupling 24, which via a first connecting pipe 26 is flow-connected to an upstream side of the centrifugal pump 18. The enclosure 14 also comprises an outlet in the form of an external, second flange coupling 28, which via a second connecting pipe 30 is flow-connected to a downstream side of the centrifugal pump 18. The inlet and outlet of the enclosure 14 are also of closeable design, in that the first flange coupling 24 is coupled to a first valve 32, whilst the second flange coupling 28 is coupled to a second valve 34. Furthermore, the valves 32, 34 can be opened or closed via associated actuator arrangements (not shown), which are connected to and driven and controlled by a remotely controlled control unit 48 in the enclosure 14. Alternatively, the valves 32, 34 may be opened or closed by means of a remotely controlled underwater vessel (“ROV”).

Each valve 32, 34 is also flow-connected to an injection pipeline 36 for transporting the injection water 10. An upstream end of the injection pipeline 36 is connected to an underwater installation 38 located on the seabed 6 and is designed for various treatment of the seawater 4, whilst a downstream end of the injection pipeline 36 is connected to a well head 40 coupled to said injection well 12 on the seabed 6 (see FIGS. 2 and 3). The seawater 4 surrounding the underwater installation 38 is used as untreated water for the injection water 10. The untreated water is drawn from a layer of water situated just above the seabed 6, and is introduced into the underwater installation 38 via an intake pipe 42 coupled thereto. The intake pipe 42 may also be provided with or connected to one or more suitable intake filters.

The enclosure 14 further contains a lubrication arrangement for lubricating various moving parts in the centrifugal pump 18 and the electric motor 20. The enclosure 14 moreover contains a cooling arrangement for removing heat that is generated by equipment inside the enclosure 14 when in operation. The enclosure 14 then also contains said remotely controlled control unit 48, which in addition to controlling said valves 32, 34 is designed for operating control of, among other things, the electric motor 20 and said lubrication arrangement and cooling arrangement. In this embodiment, the lubrication arrangement, the cooling arrangement and the control unit comprise respective units (or modules), which are vertically aligned in relation to one another, and which are also arranged side by side with the centrifugal pump 18 and the electric motor 20 (see FIG. 1). The enclosure 14 therefore contains a lower lubrication unit 44, a middle cooling unit 46 and an upper, remotely controlled control unit 48, which has already been mentioned in connection with control of said valves 32, 34. By aligning said equipment 18, 20, 44, 46, 48 vertically inside the vertically upright, cylindrical and relatively narrow enclosure 14 it is also possible to design the enclosure 14 with an outer circumference which fits inside a working aperture (“moon pool”) in a deck of a floating vessel (not shown). The enclosure 14 and its contents can thereby be transported on the deck of the vessel when shipping out to the relevant offshore location, following which the enclosure 14 can be lowered down into the seawater 4, and if necessary also retrieved from the seawater 4 via the working aperture in the deck of the vessel.

The lower lubrication unit 44 contains, among other things, a fluid lubricant (not shown) and a suitable pump (not shown) for the lubricant. Drive power and control signals to the lubricant pump are transmitted from the upper control unit 48 via a first connecting line 50. Said lubrication arrangement also comprises a first lubricant pipe loop 52 and a second lubricant pipe loop 54, which connect the lubrication unit 44 to lubricated components of the centrifugal pump 18 and the electric motor 20 respectively. In operation, the lubrication unit 44 is thereby capable of supplying such components with fluid lubricant. The direction of flow of the lubricant is moreover indicated by black arrows in FIG. 1.

The middle cooling unit 46 furthermore contains, among other things, a suitable coolant (not shown) and a suitable compressor/pump (not shown) for the coolant. Drive power and control signals to the coolant pump are transmitted from the upper control unit 48 via a second connecting line 56. Said cooling arrangement also comprises a coolant pipe loop 58, which via liquid-tight bushings (not shown) through the wall of the enclosure 14 connect the cooling unit 46 to a heat exchanger 60 arranged on the outside of the enclosure 14. In operation, the cooling unit 46 is thereby able to absorb heat that is generated by equipment inside the enclosure 14 and to transmit this heat to the heat exchanger 60 on the outside of the enclosure 14. The heat exchanger 60 exchanges the transmitted heat with colder seawater 4, which surrounds the enclosure 14. A cooled coolant can thereby be returned to the cooling unit 46 for fresh absorption of heat generated in the enclosure 14. The direction of flow of the coolant is also indicated by black arrows in FIG. 1.

In this embodiment, the enclosure 14 also contains various monitoring equipment (not shown), for example one or more cameras, associated light sources, various detectors including gas detectors, for operational monitoring of the centrifugal pump 18, the electric motor 20 and said cooling arrangement and lubrication arrangement. Drive power, control signals and monitoring data to/from such monitoring equipment are also transmitted from/to the upper control unit 48.

The upper, remotely controlled control unit 48 furthermore contains various electronic components and equipment to the extent necessary in order to achieve the required functionality of the pump system 2 in question. The control unit 48 may therefore contain various electronic processors and circuit boards, data programs, electronic circuit breakers and couplings, but also various data communications equipment, including transceivers and signal converters, and any smaller energy sources for the operation, control and/or signal transmission to/from various equipment and components in the enclosure 14, for example one or more batteries for the operation of monitoring equipment in the enclosure 14. The equipment is as such generally known, however, and will therefore not be discussed in more detail here. The control unit 48 also transmits control signals to the electric motor 20 via a third connecting line 62.

The wall of an upper part of the enclosure 14 is moreover provided with a releasable and wet-mateable plug connection 64 of the plug 64a and socket 64b type. The socket 64b is situated on the outside of the enclosure 14 and is connected to a liquid-tight bushing (not shown) through the wall of the enclosure 14, whilst the plug 64a is coupled to a separate control cable (“umbilical line”) 66, which is connected to a remote host device. The plug 64a can thereby be coupled to or uncoupled from the socket 64b by means, for example of an unmanned and remotely controlled underwater vessel (“ROV”). The control cable 66 is further designed to be capable of transmitting control signals and monitoring data between the host device and the control unit 48, and designed to be capable of transmitting drive power from the host device to powered equipment in the pump system 2. The control cable 66 therefore constitutes both a signal transmission cable and a power transmission cable. Since the electric motor 20 requires a lot of electrical drive power, a power transmission cable 68 is arranged between the electric motor 20 and a power outlet (not shown) in the socket 64b. A fourth connecting line 70 is also arranged between the socket 64b and the upper control unit 48 for transmitting control signals, monitoring data and any drive power between the remote host device and the control unit 48.

FIG. 2 shows an embodiment in which the control cable 66 is connected to a remote host device in the form of a floating platform 72 situated offshore. FIG. 3 shows another embodiment in which the control cable 66 is connected to a remote surface installation on land (not shown).

As stated, FIGS. 2 and 3 also show that the upstream end of the injection pipeline 36 is connected to said underwater installation 38, which is located on the seabed 6 for various treatment of the untreated injection water, that is to say the seawater 4, which surrounds the underwater installation 38. The seawater 4 is drawn from a layer of water situated just above the seabed 6 and is introduced into the underwater installation 38 via its intake pipe 42. This underwater installation 38 comprises, among other things, at least one arrangement (not shown) for removing solid particles from the seawater 4 without filtering. An example of such an underwater arrangement is described in said WO 2007/035106 A1, in which solid particles are precipitated out of the seawater 4 under gravity, so-called sedimentation.

In addition, the underwater installation 38 may comprise at least one arrangement (not shown) for chemical treatment of the water which runs out from the first aforementioned arrangement for the sedimentation of solid particles. The water running out is brought into contact with at least one type of water-soluble solid chemical for gradually dissolving and mixing with the water. Such water-soluble solid chemicals may consist of chlorine, biocide, oxygen-removal agents, corrosion inhibitors and/or settlement inhibitors. An example of such a chemical treatment arrangement is described in the aforementioned WO 2004/090284 A1. In this embodiment, the underwater installation 38 comprises a discharge point for the injection water 10. Following said water treatment in the underwater installation 38 and with the aid of the centrifugal pump 18 in the enclosure 14, the treated injection water 10 is pumped through said underwater pipeline 36 and onwards to the well head 40 of the injection well 12. The injection water 10 is then pumped down into the injection well 12 and into an underground oil reservoir 74 in a subsurface 76 for the secondary extraction of crude oil therefrom. The direction of flow of the injection water 10 is indicated by black arrows in all figures.

FIG. 2 also shows that the underwater installation 38 is connected to the floating platform 72 via a further control cable (“umbilical line”) for transmitting control signals, drive power and/or monitoring signals. FIG. 3, on the other hand, shows that the further control cable 78 is connected to said remote surface installation on land (not shown).

Note that the features of the above embodiments can be combined, and that the pump system 2 of FIGS. 2 and 3 may be configured as described with respect to FIG. 1.

Claims

1. A pump system (2) for transporting injection water (10) to an underwater injection well (12), where the pump system (2) comprises a pressure-tight enclosure (14) located underwater and containing: where the enclosure (14) also comprises: characterized in that the inlet (24) of the enclosure (14) is flow-connected to a body of water (4), in which the enclosure (14) is located, water from this body of water (4) being used as injection water (10) to said underwater injection well (12); and

a pump arrangement (18) for pumping the injection water (10);

a drive arrangement (20) connected to the pump arrangement (18) for operation of the latter;

a cooling arrangement (46) for removing heat from the interior of the enclosure (14); and

at least one control unit (48) for operating control of at least said drive arrangement (20);

an inlet (24) which is flow-connected to an upstream side of the pump arrangement (18); and

an outlet (28) which is flow-connected to a downstream side of the pump arrangement (18),

the outlet (28) of the enclosure (14) is flow-connected to the injection well (12).

2. The pump system (2) as claimed in claim 1, characterized in that the pressure-tight enclosure (14) contains a lubrication arrangement (44) for lubricating at least one moving part in the pump arrangement (18) and the drive arrangement (20).

3. The pump system (2) as claimed in claim 1, characterized in that the pump arrangement (18) and the drive arrangement (20) are provided with magnetic bearings for the operating support of at least one rotating part in the pump arrangement (18) and the drive arrangement (20);

the magnetic bearings are connected to at least one control unit (48) for operating control of the bearings; and

the magnetic bearings are connected to at least one source for supplying drive power to the bearings.

4. The pump system (2) as claimed in claim 1, characterized in that the pressure-tight enclosure (14) contains monitoring equipment for operational monitoring of at least said pump arrangement (18), drive arrangement (20) and cooling arrangement (46);

the monitoring equipment is connected to at least one said control unit (48) for operating control of the monitoring equipment and the transmission of monitoring data to a remote host device (72); and

the monitoring equipment is also connected to at least one source for supplying drive power to the monitoring equipment.

5. The pump system (2) as claimed in claim 1, characterized in that the pressure-tight enclosure (14) contains a gas (17) at atmospheric or virtually atmospheric pressure, preferably at a pressure between about 1 bar and about 2 bar.

6. The pump system (2) as claimed in claim 5, characterized in that the enclosure (14) is connected via a cabled connection (66) to a remote host device (72) for transferring contaminated gas (17) from the enclosure (14) and for returning uncontaminated gas (17) to the enclosure (14).

7. The pump system (2) as claimed in claim 1, characterized in that the pump arrangement (18) and drive arrangement (20) are vertically aligned in relation to one another.

8. The pump system (2) as claimed in claim 7, characterized in that the drive arrangement (20) is mounted vertically above the pump arrangement (18).

9. The pump system (2) as claimed in claim 1, characterized in that the enclosure (14) is designed with an outer perimeter that fits inside a working aperture in a deck of a floating vessel, the vessel being designed to be capable of lowering the enclosure (14) down into the water via said working aperture in the deck of the vessel.

10. The pump system (2) as claimed in claim 1, characterized in that the enclosure (14) has a height that is greater than the largest horizontal transverse dimension of the enclosure (14).

11. The pump system (2) as claimed in claim 1, characterized in that the enclosure (14) is connected via a cabled connection (66) to a remote host device (72) for transmitting both control signals to the control unit (48) and drive power to powered equipment in the pump system (2).

12. The pump system (2) as claimed in claim 1, characterized in that said cooling arrangement (46) comprises:

at least one closed flow circuit (58) containing a coolant, where the closed flow circuit (58) is connected to the internal atmosphere of the enclosure (14) for absorbing heat therefrom, and where the closed flow circuit (58) comprises a heat exchanger (60), which is connected to said body of water (4) on the outside of the enclosure (14) for removing heat transmitted from the internal atmosphere of the enclosure (14) via the coolant of the flow circuit (58); and

a means of delivery for the coolant.

13. The pump system (2) as claimed in claim 1, characterized in that said cooling arrangement (46) comprises an open flow circuit containing a coolant, where the open flow circuit is connected to the internal atmosphere of the enclosure (14) for absorbing heat therefrom, and wherein the open flow circuit is connected to a remote host device (72) for at least the circulation of the coolant, and for removing heat transmitted from the internal atmosphere of the enclosure (14) by means of the coolant of the flow circuit.

14. The pump system (2) as claimed in claim 2, characterized in that said lubrication arrangement (44) comprises:

at least one closed flow circuit (52, 54) containing a fluid lubricant, where the closed flow circuit (52, 54) is connected to lubricated equipment in the pump system (2); and

a means of delivery for the fluid lubricant.

15. The pump system (2) as claimed in claim 2, characterized in that said lubrication arrangement (44) comprises an open flow circuit containing a fluid lubricant, where the open flow circuit is connected to lubricated equipment in the pump system (2), and where the open flow circuit is connected to a remote host device (72) for at least the circulation of the fluid lubricant, and for lubricating the lubricated equipment in the pump system (2).

16. The pump system (2) as claimed in claim 1, characterized in that the wall of the enclosure (14) is provided with at least one wet-mateable plug connection (64) designed for coupling to a separate, cabled connection (66) for transmitting both control signals to the control unit (48) and drive power to powered equipment in the pump system (2).

17. The pump system (2) as claimed in claim 4, characterized in that said remote host device (72) is a surface installation on land or offshore.

18. The pump system (2) as claimed in claim 1, characterized in that the enclosure (14) is flow-connected to at least one underwater installation (38) for treatment of the injection water (10); and

said underwater installation (38) is located underwater in said body of water (4).

19. The pump system (2) as claimed in claim 18, characterized in that said underwater installation (38) comprises at least one arrangement for removing solid particles from the injection water (10) without filtering.

20. The pump system (2) as claimed in claim 17, characterized in that said underwater installation (38) comprises at least one arrangement for chemical treatment of the injection water (10).

21. The pump system (2) as claimed in claim 18, characterized in that said underwater installation (38) comprises at least one arrangement for the destruction of organic material in the injection water (10).

22. A method for transporting injection water (10) to an underwater injection well (12), where the method uses a pump system (2) comprising a pressure-tight enclosure (14), which includes: wherein the enclosure (14) also comprises: wherein the method comprises the following steps: (A) lowering the pressure-tight enclosure (14) down into the water and locating the enclosure (14) underwater, characterized in that the method also comprises the following steps: (B) flow-connecting the inlet (24) of enclosure (14) to a body of water (4) in which the enclosure (14) is located, water from this body of water (4) being used as injection water (10) to said underwater injection well (12); (C) flow-connecting the outlet (28) of the enclosure (14) to the injection well (12); and (D) starting said drive arrangement (20) and thereby the pump arrangement (18) in order thus to pump the injection water (10) onwards to the injection well (12).

a pump arrangement (18) for pumping the injection water (10);

a drive arrangement (20) connected to the pump arrangement (18) for operation of the latter;

a cooling arrangement (46) for removing heat from the interior of the enclosure (14); and

at least one control unit (48) for operating control of at least said drive arrangement (20);

an inlet (24), which is flow-connected to an upstream side of the pump arrangement (18); and

an outlet (28), which is flow-connected to a downstream side of the pump arrangement (18);

23. The method as claimed in claim 22, characterized in that the method also comprises the following steps:

aligning the pump arrangement (18) and the drive arrangement (20) vertically in relation to one another;

designing the enclosure (14) with an outer perimeter that fits inside a working aperture in a deck of a floating vessel; and

lowering the enclosure (14) down into the water via the working aperture in the deck of the vessel.

24. The method as claimed in claim 22, characterized in that the method also comprises the following steps:

locating at least one underwater installation (38) for treatment of the injection water (10) underwater in said body of water (4); and

flow-connecting the enclosure (14) to said underwater installation (38) for treatment of the injection water (10).

25. The use of a pump system (2) as claimed in claim 21 for transporting injection water (10) to an underwater injection well (12).

26. The use of a method as claimed in claim 22 for transporting injection water (10) to an underwater injection well (12).