Patent Description:
Also, the invention relates to a method for manufacturing such an offshore water production facility.

Enhanced Oil Recovery (EOR) is a principle where oil is extracted from a reservoir or well by additional (mechanical) means. EOR increases the amount of oil that can be recovered from a field. EOR can be achieved by means of water injection. EOR comes into play during the latter stages of the field. Therefore, a water injection package is frequently added to a surface vessel after the vessel has been on station for a while. The surface vessel should have space available to locate this package, and should have (weight) capacity available. This may not always be the case. Alternatively, if there are accommodations for weight and space, the surface vessel is not operated at maximum payload capacity for a large part of its life.

It is an objective of the present application to overcome or mitigate these disadvantages. <CIT> discloses an offshore wind turbine and subsea well water injection system.

The objective is achieved by an offshore water production facility to be located on a body of water comprising a floating object, at least one wind turbine, a power generator that is coupled to the wind turbine and a water production system,.

wherein the water production system is configured for subsea well water-injection and comprises an ultra-filtration unit and a membrane de-aeration unit for water to be injected.

The invention provides an offshore water production facility that due to the fact that ultra-filtration and membrane de-aeration requires much less space, is lighter and consumes less power than prior art systems that use larger sized filtration towers (or filtration beds) and de-aeration units.

The invention provides enhanced oil recovery through inserting quality water into the hydrocarbon reservoir, in which the quality water is produced by renewable energy. Also, the offshore water production facility can be operated independently of oil or gas production facilities such as FPSO. The offshore water production facility can be located close to a water injection well at a substantial distance from the surface facility. This also reduces the costs for the water injection riser. Furthermore, the offshore water production facility is relocatable and can be positioned above a hydrocarbon reservoir on demand. The oil or gas production facilities do not require to reserve deck space for the water production system.

Additionally, the invention relates to a method for manufacturing an offshore water production facility, that comprises:.

wherein the water production system is configured for subsea well water-injection and comprises an ultra-filtration unit and a membrane de-aeration unit.

Moreover according to an embodiment, the method provides that the process equipment deck, the at least one wind turbine and the water production system are installed on the floating object at a quay side location of a floating object production facility. Advantageously, this embodiment allows installation of equipment with relatively low difficulty as the environmental conditions, wind and waves, are much more reduced at quayside than on site.

Advantageous embodiments are further defined by the dependent claims.

The invention will be explained in more detail below with reference to drawings in which illustrative embodiments thereof are shown. The drawings are intended exclusively for illustrative purposes and not as a restriction of the inventive concept. The scope of the invention is only limited by the definitions presented in the appended claims.

In the drawings elements with the same reference number refer to same or corresponding elements.

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto.

<FIG> shows schematically an offshore site <NUM> above a hydrocarbon reservoir including a wind powered offshore water production system <NUM> according to an embodiment.

At the offshore site a production vessel <NUM> such as a floating production and offloading facility FPO(or a floating production storage and offloading facility, FPSO) for hydrocarbons or an FPU i.e., a semi-submersible or a TLP (Tension Leg Platform), is located at sea <NUM> above a subsea hydrocarbon reservoir. The production vessel <NUM> may be any type of hydrocarbon production facility that is moored at the location. Any type of mooring system (not shown) such as spread mooring or turret mooring can be used to moor the production vessel. The production vessel is coupled by risers (not shown) to one or more production wells on the seabed from which hydrocarbons are collected. Over time, during the exploitation of the hydrocarbon reservoir the pressure of the wells will decrease which will complicate the hydrocarbons production. To enhance the hydrocarbons production water is injected into the hydrocarbons reservoir at an injection location <NUM> on the seabed. The injection location is typically at a substantial distance from the hydrocarbon well(s) and the location of the production vessel <NUM>.

According to an embodiment, the water injection is provided by an offshore water production facility <NUM> that is embodied by a floating object that is equipped with a water production system <NUM> and a power supply to operate the water production system. The power supply is based on a renewable energy source such a wind turbine driven power generator <NUM>, <NUM>.

According to such an embodiment, the floating object comprises a plurality of buoyancy assemblies <NUM> that support at least one column <NUM> on which a wind turbine <NUM> and power generator <NUM> are mounted.

As shown in <FIG>, the floating object consists of a truss-structure with a number of buoyancy assemblies <NUM> that support a central column <NUM> with at least one radial connecting element <NUM> to each buoyancy assembly. The buoyancy assemblies are interconnected by transverse connecting elements <NUM>.

The water production system <NUM> of which an embodiment will be described with reference to <FIG>, is arranged to take in seawater and after treatment of the seawater, to transport water to the subsea injection point(s) <NUM> through a water injection riser <NUM>. Also, an umbilical <NUM> may be running between the floating object and the subsea injection point(s) <NUM> for transporting electric power and/or control signals.

The floating object is positioned in the vicinity of, or at the location of, the subsea injection point(s) <NUM> by a mooring system <NUM>. In the seabed anchor points <NUM> are provided that are connected to the floating object by means of (taut) mooring lines or tendons <NUM>.

To provide remote control from the floating production vessel <NUM> to the offshore water production facility a communication system <NUM>, <NUM>, preferably a wireless communication system, is provided on the floating production vessel and the offshore water production facility.

<FIG> schematically shows a layout of a water production system <NUM> according to an embodiment.

The water production system <NUM> comprises an ultra-filtration unit <NUM>, a membrane de-aeration unit <NUM>, a sulfate recovery unit <NUM>, a water lift pump <NUM>, a water feed pump <NUM>, and a water injection pump <NUM>.

The water lift pump <NUM> is arranged to take in seawater. An outlet of the water lift pump <NUM> is connected to an input of the ultra-filtration unit <NUM> via an inlet (coarse) filter <NUM>. The ultra-filtration unit <NUM> is arranged to produce high quality treated (fresh) water from the sea water received from the water lift pump <NUM>.

An outlet of the ultra-filtration unit <NUM> is connected to an inlet of the water feed pump <NUM>. An outlet of the water feed pump <NUM> is connected to an inlet of the sulfate recovery unit <NUM> which is arranged to remove sulfate ions from the water.

An outlet of the sulfate recovery unit <NUM> is connected to an inlet of the membrane de-aeration unit <NUM> which is arranged to remove dissolved gases from the water. An outlet of the membrane de-aeration unit <NUM> is finally arranged for coupling to a subsea well water-injection system (including a high pressure water pump <NUM>).

In some embodiments, the water production system <NUM> comprises a feed system (not shown) for feeding chemical additives to the water. Such chemical additives may be used to reduce detrimental reactions of produced water within the reservoir after injection.

The water production system <NUM> is powered by the wind turbine based power generator <NUM>, <NUM> located on the column <NUM> of the floating object.

<FIG> shows a side view of a floating object according to an embodiment.

According to an embodiment, the water production system <NUM> is installed on a process equipment deck <NUM>. The process equipment deck <NUM> is mounted on the column <NUM> that carries the wind turbine <NUM> (including the power generator <NUM>). The process equipment deck <NUM> is located between the operational area of the turbine (i.e. the area covered by the diameter of the rotor) and the level of the sea surface.

According to a further embodiment, an additional boat landing deck <NUM> is installed on the column <NUM> between the process equipment deck <NUM> and the sea surface level. The boat landing deck <NUM> is used for mooring service vessels that may deliver chemicals and other materials for use with the water production system <NUM>.

In an embodiment the boat landing deck <NUM> has an area that is substantially smaller than the area of the process equipment deck <NUM>.

<FIG> shows a top view layout of a process equipment deck <NUM> in accordance with an embodiment.

On the process equipment deck <NUM> components of the water production system <NUM> are mounted in a manner that the point of gravity (in horizontal directions) does not significantly change with respect to a column supporting only a wind turbine based power generator.

In the embodiment shown, the water production system <NUM> comprises as components a pair of ultra-filtration units <NUM>, a pair of membrane de-aeration units <NUM> and a pair of sulfate recovery units <NUM>. Also, the water injection pump <NUM> that feeds the produced water to the subsea water injection points <NUM> is shown in the layout.

An area of the process equipment deck <NUM> is reserved as lay-down area <NUM> for goods delivered by a service vessel. A crane <NUM> is positioned adjacent to the lay-down area <NUM> for moving the goods across the deck.

Optionally, a second crane can be provided on the process equipment deck outside of the lay-down area.

The layout of the water production system components on the process equipment deck <NUM> may be such that the lay-down area <NUM> is positioned in a sector of the process equipment deck <NUM> above and overlapping the boat landing deck <NUM>. The components of the water production system <NUM> may be arranged in a manner that high-risk equipment and the storage of chemicals is not in the lay-down area <NUM> of the process equipment deck that overlaps with the area of the boat landing deck <NUM> below it.

<FIG> schematically shows a diagram for a water production system <NUM> outside of the scope of the invention.

The water production system <NUM> and the wind-turbine based power generator <NUM>, <NUM> are arranged on or in a floating object <NUM>.

The water production system <NUM> processes a flow <NUM> of incoming sea water into a flow <NUM> of high quality water that is to be injected by a water injection pump <NUM> in a subsea hydrocarbon reservoir. The power generator <NUM> supplies power <NUM> to the components <NUM>, <NUM>, <NUM>, <NUM> of the water production system <NUM>. In this embodiment, optionally, a sulfate recovery <NUM> may be installed as well.

The floating object <NUM> can be embodied as a floating tower structure supported by a truss-structure of buoyancy assemblies as described above with reference to <FIG>, <FIG>. Alternatively, the floating object <NUM> may be embodied as a semi-submersible structure <NUM> which carries at least one column <NUM> on which a wind turbine <NUM> and power generator <NUM> are mounted. The submersible structure <NUM> may be arranged to carry two or more columns that each support a wind turbine and power generator.

According to an embodiment, the offshore water production facility is manufactured according to a method which comprises:.

Preferably, the at least one wind turbine <NUM>, the power generator <NUM> and the water production system <NUM> are installed on the floating object at a quayside location of a floating object production facility. Installing the wind turbine and power generator and the components of the water production system at the quayside location reduces the costs and effort significantly as working conditions at quayside are typically better than at an offshore location.

Claim 1:
An offshore water production facility to be located on a body of water and comprising a floating object, at least one wind turbine, a power generator that is coupled to the wind turbine and a water production system,
- the floating object comprising a plurality of buoyancy assemblies that support at least one column on which a wind turbine is mounted;
- on the at least one column further a process equipment deck being mounted below an operating area of the wind turbine and above a water surface level;
- the water production system being arranged on the process equipment deck, wherein the water production system is configured for subsea well water-injection and comprises an ultra-filtration unit and a membrane de-aeration unit for water to be injected.