A network and network processing

Abstract

Apparatus and methods for modifying at least one performance parameter as a subsea location are disclosed. A method of modifying at least one performance parameter at a subsea location comprises the steps of, at a master subsea node (240), receiving respective input data from each of at least one sensor element (340) at a respective at least one slave subsea node (250); determining if the respective input data is associated with a respective performance parameter that satisfies a predetermined first characteristic; if the respective performance parameter does not satisfy the predetermined first characteristic, providing the respective input data to the topside node (210) or if the respective performance parameter satisfies the predetermined first characteristic, via a master processor element at the master subsea node, responsive to at least said input data, determining if a performance parameter associated with a selected slave subsea node should be modified; and responsive to determining if the performance parameter should be modified, providing a command signal indicating that the performance parameter should be modified from the master subsea node to at least said a selected subsea node.

Description

[0001] A NETWORK AND NETWORK PROCESSING

[0002] TECHNICAL FIELD

[0003] The present invention relates to a method and apparatus for modifying parameters in a subsea network. In particular, but not exclusively, the present invention relates to determining whether a performance parameter, such as an operating pressure or ratio of component parts in a mixture, should be modified at a slave subsea node, a master subsea node or a topside node and if the performance parameter should be modified, assessing how the performance parameter should be modified and actuating a local change in a mode of operation of subsea equipment thereby modifying the performance parameter.

[0004] BACKGROUND

[0005] In the oil and gas industry, from time to time subsea wells are used to extract petroleum and / or natural gas from a site such as an oil well or the like. Control and monitoring of one or more subsea wells is conventionally achieved through communication between a topside location such as a surface platform, a floating production storage and offloading (FPSO) or the like, and a subsea well, via an umbilical. The topside location usually contains a master control which provides monitoring and control of subsea wells topside. The master control is usually controlled by an operator. Conventionally an umbilical carries lines for electrical power, hydraulic supply and data communications between the topside location and a subsea distribution point. From the distribution point flying leads are conventionally utilised to connect the distribution point and thus the master control located topside to control modules associated with each of the subsea wells in a subsea field. Sometimes there may be more than one umbilical from the master control to more than one of various distribution points and thereby to one or more control modules associated with a subsea well. Nevertheless, data transmitted to and from a given control module to the master control passes through an umbilical.

[0006] At a subsea well such as an oil well, gas well, water injection well, or the like, a so-called Christmas tree (or ‘subsea tree’ in particular) regulates the flow of fluid out of the subsea well. The subsea tree is usually an assembly of sub-components including a control module among other things. The control module (commonly referred to as a ‘control pod’) provides an interface between control lines which usually supply hydraulic power, electric power, and signals from a host facility such as the distribution point and the subsea tree to be controlled. That is to say the control module acts as a control system for the subsea tree / manifold valves. The control module usually contains at least one component called an electronics module. The electronics module is a component of the control module which manages electrical systems on the control module, receives sensor information, processes sensor and other information, stores information and issues instructions to other components of the control module.

[0007] Among other things, the electronics module is provided with data values captured by sensors associated with the subsea tree such as temperature, pressure, and the like. Data values are regularly captured by a given sensor based on sensor readings of real-world variables associated with the subsea tree and then sent as transmitted data to the electronics module which monitors the data values and may log the data values or send all or some data values to the master control via the umbilical. Data values received by the master control are usually presented to and interpreted by the operator to diagnose issues. The operator may then choose to take positive action if required by issuing commands to the electronics module to affect the real world variables associated with the subsea tree.

[0008] Conventionally the umbilical has a limited bandwidth for transferring data between a subsea well associated with an electronics module and the master control. Therefore, the provision for sending data values captured by a sensor is somewhat limited. This can cause many problems. To give some examples, in the event of a fault, the amount of fault data logging that can be sent to the master control is limited. Often data is missed due to a lack of fidelity / resolution. This makes timely decision making and fault finding difficult. A lack of fidelity / resolution may mean that an operator has to be more proactive / experienced in what to look for to make educated guesses to diagnose the issues. Some faults in the subsea well might go unnoticed, or even if they are noticed, the retrospective operator action might have missed the issue, as the anomalous / fault behaviour is no longer occurring. In some situations, potentially helpful real world information was produced before the event was detected and the operator began monitoring the associated data values which means potentially relevant data in the build up to said event is lost. The delaying or missing of sensor data / information that can be used to diagnose or treat a problem can have significant consequences for a subsea well. In some instances, taking longer to treat a problem could reduce the efficiency of the subsea well operation, costing money. In some instances where a problem is missed due to a lack of fidelity / resolution of sensor data / information, the subsea well operation may have to be temporarily halted, a significant undesirable and expensive consequence for a subsea well operation. In current control systems, data values monitored by an electronics module in a subsea tree are transmitted, via an umbilical, to master control which is located topside. At a master control station instructions are determined to optimise operation of the subsea tree and then the instructions are transmitted back via the umbilical to the electronics module in the subsea tree to be executed. Many of the current control system solutions are often reliant on getting enough accurate data from subsea to topside to then analyse and make changes. The current systems are limited by the amount of data that can be sent topside: sometimes the bandwidth limitations from subsea to topside can limit those optimisations and stop the well from performing at its most efficient.

[0009] SUMMARY OF THE INVENTION

[0010] It is an aim of the present invention to at least partly mitigate one or more of the above- mentioned problems.

[0011] It is an aim of certain embodiments of the present invention to help a subsea field to operate more efficiently.

[0012] It is an aim of certain embodiments of the present invention to provide a method for modifying performance parameters that may be either a ‘local decision’ or a ‘network decision’.

[0013] It is an aim of certain embodiments of the present invention to provide a method for determining whether a performance parameter is a ‘local decision’; that is it does not affect other wells in a subsea field.

[0014] It is an aim of certain embodiments of the present invention to help reduce the time taken by an operator of a Master Control System (MCS) to diagnose and act upon an issue associated with a subsea well or a subsea tree.

[0015] It is an aim of certain embodiments of the present invention to provide apparatus for determining how to optimise the operation of a subsea tree at the subsea tree or other subsea infrastructure without referring to master control located topside.

[0016] It is an aim of certain embodiments of the present invention to provide a method for decentralising decision-making aspects of subsea field operation. It is an aim of certain embodiments of the present invention to introduce a hierarchy for decision making in a decentralised control system.

[0017] It is an aim of certain embodiments of the present invention to help reduce conflicts between modifying performance parameters of different subsea trees.

[0018] It is an aim of certain embodiments of the present invention to provide a method for reducing a workload of a human operator at a master control station (MCS).

[0019] It is an aim of certain embodiments of the present invention to provide a method for reducing human error in a subsea production system.

[0020] It is an aim of certain embodiments of the present invention to provide a method for increasing a speed of data analysis of input sensor data and optionally increase a speed of responding to said sensor input sensor data.

[0021] According to a first aspect of the present invention there is provided a method of modifying at least one performance parameter at a subsea location, comprising the steps of: at a first subsea node, receiving respective input data from each of at least one sensor element; via a processor element at the first subsea node, determining if the input data is associated with a respective performance parameter that satisfies a predetermined first condition; and if the respective performance parameter satisfies the predetermined first condition, via the processor element at the first subsea node, determining if the performance parameter should be modified and if so actuating a local change in a mode of operation thereby modifying the performance parameter.

[0022] Aptly, the method further comprises: if the respective performance parameter does not satisfy the predetermined first condition, designating the first subsea node as a first slave subsea node; providing the input data and / or analysis data, determined at the first slave subsea node and responsive to the input data, to a master processor element at a master subsea node, remote from said first slave subsea node, that is connected via a first communication link to the first slave subsea node and, via at least one respective further communication link, to a respective at least one further slave subsea node; and receiving a command signal indicating that the performance parameter should be modified via the first communication link at the first slave subsea node and, at the first slave subsea node in response to the command signal, actuating a local change in a mode of operation thereby modifying the performance parameter.

[0023] Aptly, the method further comprises: determining if the respective performance parameter satisfies the predetermined first condition by determining if the performance parameter is on an allowed local control list that identifies performance parameters that can be modified locally.

[0024] Aptly, the method further comprises: determining if the performance parameter should be modified by determining if a sensed value for the performance parameter in the input data reaches or falls below a respective threshold value.

[0025] Aptly, the method further comprises: determining if the performance parameter should be modified by determining if a trend in change of a value for the performance parameter in the input data indicates that the sensed value will reach or fall below a respective threshold value in a pre-set future time period and modifying the performance parameter prior to the sensed value reaching or falling below the respective threshold value.

[0026] Aptly, the method further comprises: actuating the local change by generating at least one command signal at the subsea node and, providing the command signal to at least one subsea auxiliary equipment element proximate to the slave subsea node and, responsive to the command signal, varying operation of the auxiliary equipment.

[0027] Aptly, the method further comprises: actuating the local change by receiving at least one command signal, from a master subsea node, at the slave subsea node and providing the command signal to at least one subsea auxiliary equipment element proximate to the slave subsea node and, responsive to the command signal, varying operation of the auxiliary equipment. Aptly, the method further comprises: the auxiliary equipment element comprises a subsea actuator, that optionally is a hydraulic or pneumatic or electric actuator, or a subsea valve that optionally is a control or isolation valve.

[0028] According to a second aspect of the present invention there is provided a method of modifying at least one performance parameter at a subsea location, comprising the steps of: at a master subsea node, receiving respective input data from each of at least one sensor element at a respective at least one slave subsea node; determining if the respective input data is associated with a respective performance parameter that satisfies a predetermined first characteristic; if the respective performance parameter does not satisfy the predetermined first characteristic, providing the respective input data to a topside node or if the respective performance parameter satisfies the predetermined first characteristic, via a master processor element at the master subsea node, responsive to at least the respective input data, determining if a performance parameter associated with a selected slave subsea node should be modified; and responsive to determining if the performance parameter should be modified, providing a command signal indicating that the performance parameter should be modified from the master subsea node to at least said a selected subsea node.

[0029] Aptly, the method further comprises: providing the input data to the master processor element via a first communication link between the master subsea node and said a selected slave subsea node; and providing the command signal via the first communication link.

[0030] Aptly, the method further comprises: at the master processor at the master subsea node, prior to generating the command signal, receiving input data from one or more sensors of a plurality of slave subsea nodes; determining how local changes in modes of operation at the plurality of slave subsea nodes are advisable to balance performance across multiple local sites of a field site; and responsive to determining advisable changes to balance performance, generating a plurality of command signals and respectively providing each of those generated command signals to a plurality of slave subsea nodes.

[0031] Aptly, the method further comprises: determining if the performance parameter should be modified by determining if a sensed value for the performance parameter in the input data reaches or falls below a respective threshold value.

[0032] Aptly, the method further comprises: determining if the performance parameter should be modified by determining if a trend in change of a value for the performance parameter in the input data indicates that the sensed value will reach or fall below a respective threshold value in a pre-set future time period and modifying the performance parameter prior to the sensed value reaching or falling below the respective threshold value.

[0033] Aptly, the method further comprises: at the master subsea node, receiving performance target data from a topside node and determining if the performance parameter associated with at least one slave subsea node should be modified responsive to the performance target data and said at least said input data.

[0034] Aptly, the method further comprises: receiving the performance target data at the master subsea node via a further communication link, comprising a communication link provided via an umbilical, between the master subsea node and a topside control station.

[0035] Aptly, the method further comprises: prior to providing said a command signal, providing aggregate data, comprising data responsive to respective input data received at the master subsea node from a plurality of slave subsea nodes, to the topside node; and responsive to an approval signal received at the master subsea node from the topside node, providing said a command signal to at least the selected slave subsea node.

[0036] Aptly, the method further comprises: repeatedly providing aggregate data to the topside node with proposal data that comprises data, determined at the master subsea node, indicating a proposed local change in a mode of operation at at least one subordinate slave subsea node subordinate to the master subsea node; receiving, at the master subsea node, one-by-one, a respective approval signal from the topside node; and modifying respective performance parameters at said at least one subordinate slave subsea node over a period of time responsive to the approval signals received one-by-one at the master subsea node.

[0037] According to a third aspect of the present invention there is provided apparatus for modifying at least one performance parameter at a subsea location, comprising: a plurality of slave subsea nodes each receiving respective input data from each of at least one sensor element and each comprising a respective at least one slave processor element for determining if the corresponding input data is associated with a respective performance parameter that satisfies a predetermined first condition; and at least one master subsea node each connected to a respective at least one subordinate slave subsea node and disposed to receive respective input data from each subordinate slave subsea node; wherein the master subsea node comprises a master processor element for determining if a respective performance parameter should be modified if the slave processor element determines that the input data is not associated with a respective performance parameter that satisfies the predetermined first condition.

[0038] Aptly, each slave subsea node is connected via a respective first communication link to a respective master subsea node to which said each slave subsea node is subordinate; and at least one master subsea node is connected to a topside node via a further communication link provided via an umbilical.

[0039] Aptly, each subsea node comprises an allowed local control list accessible to a respective slave processor element, said local control list comprising data indicating performance parameters that can be modified locally at an associated slave subsea node and / or each master subsea node comprises an allowed network control list accessible to a respective master processor element, said network control list comprising data indicating performance parameters that should be modified at the master subsea node. Aptly, a communication network is an interconnected group of nodes that can communicate with each other via one or more connections. A connection can be provided via a respective one or more communication link.

[0040] Aptly, the one or more connections may be wired connections, wireless connections, or the like.

[0041] Aptly, a node is a virtual point in a communication network.

[0042] Aptly, a topside node is a node that is associated with a physical location on / at the surface of a body of water.

[0043] Aptly, a subsea node is a node that is associated with a physical location under the surface of a body of water, at a depth of 1m, 10m, 500m, 10km or more below the surface of a sea, lake, or the like. Subsea thus indicates under a body of water rather than just under a sea surface.

[0044] Aptly, a subsea node is associated with a physical location that is vertically offset by 1m, 10m, 500m, 10km or more from the surface of a body of water and / or a neighbouring subsea node, and that is horizontally offset by 1m, 10m, 500m, 10km or more from the neighbouring subsea node.

[0045] Aptly, a topside node is a node that is physically located on / at the surface of a body of water.

[0046] Aptly, a subsea node is a node that is physically located under the surface of a body of water, at a depth of 1m, 10m, 500m, 10km or more below the surface of a sea, lake, or the like.

[0047] Aptly, a topside node is an FPSO.

[0048] Aptly, a topside node is a surface platform.

[0049] Aptly, a topside node is a topside component.

[0050] Aptly, a subsea node is an SCM, SEM, distribution unit, manifold, PCDM, OEM, subsea tree, or the like. Aptly, a subordinate slave subsea node is a slave subsea node associated with a respective master subsea node. So each master subsea node has one or more slave subsea nodes subordinate to it and thus associated with it.

[0051] Aptly, a selected slave subsea node is a slave subsea node that may have a performance parameter modified responsive to a decision / command signal issued by a master subsea node.

[0052] Aptly, aggregate data and proposal data are data that are compiled at a master subsea node and then sent to a network master node. The aggregate data and / or proposal data helps indicate a proposed change to be made at at least one slave subsea node. This makes it easier for a topside operator to approve the proposed change.

[0053] Aptly, a network master node is a topside node and may be aligned with a master control system (MCS).

[0054] Aptly, providing the input data to a master processor element includes input data from each of at least one sensor element and analysis data from analysing said input data.

[0055] Aptly, a performance parameter is a mean health status of a part.

[0056] Aptly, the network master is a topside node.

[0057] According to a fourth aspect of the present invention there is provided a method of modifying at least one performance parameter at a subsea location, comprising the steps of: at a master subsea node, receiving respective input data from each of at least one sensor element at a respective at least one slave subsea node; determining if the respective input data is associated with a respective performance parameter that satisfies a predetermined first characteristic; if the respective performance parameter does not satisfy the predetermined first characteristic, providing the respective input data to the topside node or if the respective performance parameter satisfies the predetermined first characteristic, via a master processor element at the master subsea node, responsive to at least the respective input data, determining if a performance parameter associated with a selected slave subsea node should be modified; and responsive to determining if the performance parameter should be modified, providing a command signal indicating that the performance parameter should be modified from the master subsea node to at least said a selected subsea node.

[0058] Certain embodiments of the present invention provide an operator with additional information that aids them to make better and quicker decisions around faults and production issues.

[0059] Certain embodiments of the present invention provide better use of available bandwidth whether possible, ensuring that the most pertinent data is sent topside for immediate analysis and rapid operator decision making.

[0060] Certain embodiments of the present invention provide a method of removing conflict between decision determining elements of a decentralised control system.

[0061] Certain embodiments of the present invention provide apparatus for automating subsea production tasks.

[0062] Certain embodiments of the present invention provide a method for optimisation of the whole oil field operation.

[0063] Certain embodiments of the present invention provide a method for optimisation of a subsea site associated with a master subsea node.

[0064] Certain embodiments of the present invention reduce the burden on an operator, allowing them to simply view the results of performance parameter analysis and then authorised the suggested performance parameter modification / s.

[0065] Certain embodiments of the present invention provide a method for helping to identify a nearoptimum performance parameter value.

[0066] Certain embodiments of the present invention provide apparatus for controlling a subsea electronics module (SEM) behaviour for specific tasks and then analyse the results and then suggest an optimisation that could be implemented. Certain embodiments of the present invention provide apparatus for automating modification of performance parameters that satisfy a predetermined condition. A report of local changes in a mode of operation that have been actuated are then provided to a master control station (MCS) and / or operator.

[0067] BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

[0069] Figure 1 illustrates a subsea field with multiple installation wells;

[0070] Figure 2 illustrates a schematic diagram of a subsea control system;

[0071] Figure 3 illustrates a subsea well configuration;

[0072] Figure 4 illustrates a master subsea node configuration;

[0073] Figure 5 illustrates a slave subsea node configuration;

[0074] Figure 6 illustrates a table for determining a local decision;

[0075] Figure 7 illustrates a table for determining a network decision;

[0076] Figure 8 illustrates a method of modifying performance parameters at a subsea node;

[0077] Figure 9 illustrates a method of modifying performance parameters at a master subsea node; and

[0078] Figure 10 illustrates a schematic diagram of an alternative subsea control system.

[0079] In the drawings like reference numerals refer to like parts.

[0080] DETAILED DESCRIPTION Figure 1 illustrates a subsea field 100 below a sea surface 110 where a first subsea site 115, a second subsea site 116 and a third subsea site 117 are located. It will be appreciated that there may alternatively be one, two, four or more subsea sites 115, 116, 117 in the subsea field 100. At the first subsea site 115 there are multiple wells 120i ,2 (two shown). The second and third subsea sites 116, 117 also have multiple subsea wells 120 (not shown). It will be appreciated that the subsea site 115, 116, 117 may alternatively have one, two, three, four or more subsea wells 120. The subsea site 115, 116, 117 therefore includes at least one wellhead and its respective Christmas (subsea) tree. Figure 1 thus illustrates a multiple well complex about a seabed 125.

[0081] A floating production storage and offloading (FPSO) vessel 130 is located above the field 100. It will be appreciated that alternatively, a floating platform, topside location or topside node may be provided instead of the FPSO 130. The FPSO 130 includes a topside controller 132 and an electrical power unit. The topside controller shown in Figure 1 is a master control station (MOS) 132. It will be appreciated that the MOS 132 is an example of a master controller. The MOS is an example of a topside control device. It will be appreciated that other master controllers or other topside control devices could be provided a network master node. The MCS 132 is used to generate and receive control communications to instruct operation of subsea components and to receive data indicative of the state of various components and sensor readings etc. It will be appreciated that whilst a floating structure is illustrated in Figure 1 the MCS 132 may be a shore-based control centre or a platform based node or the like. The FPSO is an example of a topside node.

[0082] The FPSO 130 is connected via a first umbilical 135i to a distribution unit 140 in the first subsea site 115. It will be appreciated that alternatively, a Remotely Operated Vehicle (ROV) may instead provide a connection between the FPSO 130 and the distribution unit 140. A topside node is a node that is physically located on / at the surface of a body of water. A subsea node is a node that is physically located under the surface of a body of water, eg at a depth of 1m, 10m, 500m, 10km or more below the surface of a sea, lake, or the like. The distribution unit 140 may be a subsea distribution unit (SDU), manifold or the like. The first umbilical 135i is terminated in a wet mating connector 145 which mates with a corresponding wet mating connector interface 150 of the distribution unit 140. It will be appreciated that alternative connectors may be used. A second umbilical 1352 connects the FPSO 130 and associated MCS to the second subsea site 116. The second subsea site 116 contains a distribution unit and subsea wells (not shown). A third umbilical 135a connects the FPSO 130 and associated MCS to the third subsea site 117. The third subsea site 117 contains a distribution unit and subsea wells (not shown). The second subsea site 116 is connected to the first subsea site 115 by a first cable 153i. The third subsea site 117 is connected to the first subsea site 115 by another first cable 1532. It will be appreciated that the distribution units in the first subsea site 115, second subsea site 116 and third subsea site 117 are interconnected by the first cables 153I,2. It will be appreciated that whilst three subsea sites 115, 116, 117 are illustrated in Figure 1 , there may alternatively be one, two, four, five, six or more subsea sites 115, 116, 117 located in the subsea field 100, operated by the single FPSO 130.

[0083] Respective second cables 16O1 ,2 connect the distribution unit 140 to each respective subsea well 120. The distribution unit 140 and subsea wells 120I,2 are arranged in a so-called star formation, where the distribution unit 140 is connected to each subsea well 120 individually. It will be appreciated that alternatively the distribution unit 140 may be connected to the subsea wells 120i ,2 in a mesh or chain formation, wherein the distribution unit 140 is connected to one subsea well 120i and each subsea well 120i is connected to a consecutive subsea well 1202. It will be appreciated that alternatively a multi-drop formation or any other formation may be used. It will be appreciated that there may alternatively be more than one distribution unit 140. It will be appreciated that the distribution unit 140 may alternatively not be a discrete element but may instead merely be a distribution point provided by a manifold or Christmas (subsea) tree or the like. In some embodiments the distribution unit 140 may be referred to as a distribution point or a distribution node.

[0084] Each subsea well 120 illustrated in Figure 1 is associated with a respective subsea control module (SCM) 170i ,2. It will be appreciated that the SCM 170 may be referred to as a control module. The SCM determines operation of hydraulic driven valves which can be opened and closed using electrical signals communicated from the FPSO 130 or other topside control centre. Each SCM 170I,2 is associated with two subsea electronics modules (SEMs) (not shown). It will be appreciated that an SCM 170 may alternatively be associated with one, three, four or more than four SEMs. It will be appreciated that the SEM may be referred to as an electronics module. It will be appreciated that alternatively, a Remotely Operated Vehicle (ROV) may instead provide a connection between the FPSO 130 and the SCM 170.

[0085] Figure 2 illustrates a schematic 200 of a subsea control system of the subsea sites 115, 116, 117 and FPSO 130. Whilst Figure 1 illustrates a physical system of topside and subsea apparatus, Figure 2 illustrates only a communication network of the physical system including a plurality of nodes. It will be appreciated that alternative subsea control system arrangements may be used instead. The communication network is an interconnected group of nodes that can communicate with each other directly or indirectly via one or more connections, whereby the one or more connections may be wired connections, wireless connections, or the like. A node is a uniquely addressable location in the communication network. The node may include one or more processing elements. A topside node is a node that is associated with a physical location on / at the surface of a body of water. A subsea node is a node that is associated with a physical location under the surface of a body of water, at a depth of 1m, 10m, 500m, 10km or more below the surface of a sea, lake, or the like. Alternatively the topside node is a node that is physically located on / at the surface of a body of water. Alternatively the subsea node is a node that is physically located under the surface of a body of water, eg at a depth of 1m, 10m, 500m, 10km or more below the surface of a sea, lake, or the like. Alternatively the topside node is an FPSO. Alternatively the subsea node is an SCM, SEM, distribution unit, manifold, PCDM, UTA, distribution node, subsea tree, or the like.

[0086] In Figure 2 there is illustrated use of a network master 210. The illustrated network master 210 is located topside. The network master 210 is associated with the FPSO 130. It will be appreciated that the topside node may alternatively be a floating platform, a land platform, or the like. It will be appreciated that the network master 210 is the node running on the Master Control Station 132 (MCS). In other words the network master 210 is a node of the MCS 132. As noted above the MCS 132 illustrated is a topside controller, so it will be appreciated that the network master node 210 may be associated with any topside controller. The network master node 210 communicates with three sub-networks 22O1-3. A first sub-network 220i corresponds to the first subsea site 115. A second sub-network 2202 corresponds to the second subsea site 116. A third sub-network 22O3 corresponds to the third subsea site 117. It will be appreciated that the network master node 210 could alternatively communicate with and / or manage one, two, four, or more sub-networks 220. Communication of data between the network master node 210 and any sub-network 220 is facilitated by the umbilical 135I-3. The umbilical 135 is a communication link. The umbilical 135I-3 contains a fibre optic connection for transferring information, although it will be appreciated that the umbilical 135i. 3 could alternatively or additionally contain a fast copper connection, a direct subscriber line (DSL) connection, 100BaseT connection, other wired connection, wireless connection or the like. The first umbilical 135i connects the network master node 210 to a first sub-network master 240i. The second umbilical 1352 connects the network master node 210 to a second sub-network master 2402. The third umbilical 135s connects the network master node 210 to a third sub-network master 240s. The first cable 153i ,2 connects one sub-network master 240i. 3 to another sub-network master 240I-3. The first cable 153I,2 is a fibre optic connection, although it will be appreciated that the first cable 153I,2 is of a first cable type and could alternatively be a fast copper connection, a direct subscriber line (DSL) connection, 100BaseT connection, other wired connection, wireless connection or the like. The first cable 153 is a communication link. The first sub-network master 240i is a node of the sub-network 220i. It will be appreciated that the first sub-network master 240i is the node running on the distribution unit 140. The second sub-network master 2402 is a node of the sub-network 2202. It will be appreciated that the second sub-network master 2402 is the node running on a second distribution unit. The third sub-network master 240s is a node of the sub-network 22O3. It will be appreciated that the third sub-network master 240s is the node running on a third distribution unit. It will be appreciated that alternatively, the sub-network masters 240 may be running on a manifold or a distribution unit or the like.

[0087] Figure 2 also shows a first sub-network node 250i. The first sub-network node 250i is a node associated with the first subsea well 120i . Similarly a second sub-network node 2502 is a node associated with the second subsea well 1202. The remaining subsea sub-network nodes 2503- 9 are associated with subsea wells 120. The sub-networks 22O1-3 are thus associated with numerous subsea wells 120. In other words, the subsea control system diagram 200 extends over nine subsea wells 120. The arrangement of the network master node 210, sub-network masters 240I-3 and sub-network nodes 250i.g shown in Figure 2 may be described as a ‘point- to-point hybrid’. That is to say there is a mesh network between the network master node 210 and sub-network masters 240I-3. Aptly there is a tree / star network between the network master node 210 and sub-network masters 240I-3. There is a tree / star sub-network between a given sub-network master 240I-3 and its sub-network nodes 250i.g. Aptly there is a mesh network between a given sub-network master 240I-3 and its sub-network nodes 250i.g. In the tree / star network the given sub-network master 240I-3 is a central hub that each sub-network node 240 is connected to via the second cable 160 (eight shown). The second cable 160 is of a second cable type and is a copper connection. It will be appreciated that alternatively the second cable 160 may be a fibre optic, fast copper, other wired or wireless connection. The second cable 160 is a communication link.

[0088] It will be appreciated that the sub-network master 240I-3 is also called a master subsea node 240I-3. Aptly the master subsea node is a hierarchical position in the communication network. Aptly the master subsea node is defined in the communication network depending on the task that is being performed. In some embodiments, the master subsea node may be a single subnetwork master 240i. In some embodiments the master subsea node may be a sub-network node 250I-9 running on a subsea tree. It will be appreciated that the sub-network node 250i.g is also called a slave subsea node 250i.g. Aptly the slave subsea node is a hierarchical position in the communication network. Aptly the slave subsea node is defined in the communication network depending on the task that is being performed. In some embodiments, the slave subsea node may be one or more sub-network masters 2402,3. In some embodiments the slave subsea node may be only one or more of the sub-network nodes 250i.g. It will be appreciated that the first and second sub-network nodes 250I,2 are subordinate slave subsea nodes associated with the first master subsea node 240i. Similarly, any subordinate slave subsea nodes are slave subsea nodes 250i.g associated with a respective master subsea node 240I,2,3. Communication links are provided between master subsea nodes 240 and slave subsea nodes 250.

[0089] Figure 3 illustrates the subsea well 120 location. At the subsea well 120 there is a wellhead 310 and a subsea tree 320. It will be appreciated that the subsea tree 320 is a type of Christmas tree, ‘XT’. Aptly the subsea tree 320 is a Christmas tree. The wellhead 310 is a structure placed on the seabed at the location of a previously-drilled subsea well 120. During normal operation, the subsea tree 320 is in fluid connection with the wellhead 310 using pipes so that fluid may flow from the wellhead 310 into the subsea tree 320. The subsea tree 320 thereby monitors and controls the flow of fluid at the well 120. The subsea tree 320 is a conventional vertical tree although it will be appreciated that a horizontal tree could be used alternatively. The subsea tree 320 includes a number of components for regulating the flow of fluid from the wellhead 310 such as valves 330, sensors 340I,2, and the like. It will be appreciated that there may be any number of valves 330 in the subsea tree 320 depending on configuration. Aptly the valves 330 may alternatively be located external to the subsea tree 320, or both internal and external to the subsea tree 320. Although two sensors are shown in Figure 3 it will be appreciated that the subsea tree 320 may alternatively have any number of sensors 340. The sensor 340 may communicate with the subsea tree 320 via an input / output (I / O) (not shown) for external sensors and / or optionally external valves. The sensor 340I,2, measures performance parameters such as wellhead 310 fluid pressure, external pressure, fluid temperature, flow rate, valve status, humidity, chemical composition, voltage, current, power, data rate, shock / impact, velocity, acceleration, magnetic field strength and the like thereby providing measurement parameters to the subsea tree 320. Aptly a performance parameter is a variable that can be measured. Aptly a performance parameter is a variable that can be modified and / or controlled. The subsea tree 320 also includes a subsea control module (SCM) 350. The SCM 350 operates and thereby controls the valves 330 of the subsea tree 320. In other words, the SCM 350 controls the subsea tree 320. The SCM 350 also receives sensor information monitored by the sensors 340I,2; sensor information may then be recorded on the SCM and / or transmitted topside to the MCS 132. That is to say, measurement data of the performance parameter monitored by a sensor 340as a measurement parameter is provided to the SCM 350. It will be appreciated that the sensor 3402 is located outside of the SCM 350, where it is connected to the SCM 350 and thereby communicates data such as measurement data back to the SCM 350. Alternatively, the sensors 340 may be located inside the SCM 350. In some embodiments, a wired connection may be used to connect the sensors 340i,2to the SCM 350 to transfer data. In other embodiments, a wireless connection (eg Bluetooth, radio telemetry, sonar, light or the like) may be used to connect the sensor 340 to the SCM 350 to transfer data. The SCM 350 includes two subsea electronics modules (SEMs) 360I,2 for redundancy. It will be appreciated that alternatively the SCM 350 may be a general control module that may include one, two, three, four, five, or more SEMs 360. The SEM 360 provides all or some of the processing capabilities of the SCM 350. In other words, the SEM 360 may use electrical signals to operate the SCM 350 thereby adjusting the flow of fluid in the subsea tree 320 based on commands from the MCS 132 and / or sensor 340i,2data. Sensor data from the sensors 340i,2,or valve data from the valves 330 are communicated to the SEM 360 via an SEM interface input / output (I / O) (not shown). The SEM 360 is a component of the SCM 350 which manages electrical systems on the SCM 350, receives sensor information, processes sensor and other information, stores information and issues instructions to other components of the SCM 350.

[0090] Figure 4 illustrates processing elements of the master subsea node 240. Aptly Figure 4 illustrates the processing elements of the distribution unit 140. It will be appreciated that the distribution unit 140 may include many other components. It will be appreciated that the distribution unit 140 may alternatively be a manifold 140. That is to say, alternatively, the processing elements shown in Figure 4 and their associated functions as described below may alternatively be located in the manifold. Aptly, the processing elements shown in Figure 4 may be located in the SEM 360I,2.

[0091] The master subsea node 240 includes a network switch 410. The network switch 410 acts as a common interface to all internal components of master subsea node 240. In other words the network switch 410 is connected and thereby in communication with all internal components of the master subsea node 240. The master subsea node 240 also includes a system controller 430. The system controller 430 manages the control of instrumentation and functions of the master subsea node 240. The system controller 430 thereby regulates operations of the master subsea node 240 including any number of: controlling processing tasks, setting performance parameters, receiving input data from associated master subsea node 240 sensors, receiving data, transmitting data, or the like. The performance parameters of the master subsea node 240 may include: temperature, humidity, chemical composition, voltage, current, power, data rate, shock / impact, pH, pressure, valve actuation, regulator actuation, system activation, water injection rates, gas injection rates, DCV states, choke positions or the like. The data received from the slave subsea node 250 includes input data, analytical data or the like. The data transmitted to the slave subsea node 250 includes a command signal or the like. Aptly the system controller 430 provides tree control and sensing function. Aptly the system controller 430 provides external interface management. Aptly the system controller 430 provides closed loop control function. Aptly the system controller 430 manages functions of the SEM 360I,2. The system controller 430 includes a processor 433 for executing one or more instructions and a non-volatile storage medium 436. The processor 433 is a 32-bit microcontroller. Aptly the processor 433 is a 16-bit, a 32-bit, a 64-bit, or the like microcontroller or a 16-bit, a 32-bit, a 64-bit, or the like microprocessor. The non-volatile storage medium 436 is a hard-disk drive. Aptly the non-volatile storage medium 436 is a flash storage, disc storage, or the like.

[0092] The master subsea node 240 includes a communication interface440. The communication interface 440 may be a subsea-to-topside (STS) modem. Alternatively the communication interface 440 may be a fibre optic interface or the like which does not require a modem. The communication interface 440 is in communication with the network master node 210. In other words the communication interface 440 is in communication with the MCS 132 via the umbilical 135. The communication interface 440 thus provides a communication interface to topside. It will be appreciated that in some embodiments, where the processing elements shown in Figure 4 are alternatively located on the SEM 360, the communication interface 440 may serve little or no function. The master subsea node 240 includes a subsea (S) modem 450. The S modem 450 is in communication with any combination of: at least one distribution unit 140, at least one SEM 360, at least one ROV, or the like. In other words the S modem 450 provides a communication interface to other subsea components including subordinate slave subsea nodes 250 and / or the master subsea nodes 240. The subordinate slave subsea nodes 250 are associated with the respective master subsea node 240. It will be appreciated that the communication interface 440 and / or modem 450 may include at least one processor for executing one or more instructions (not shown) and optionally at least one non-volatile storage medium (not shown).

[0093] Figure 4 also illustrates a decision controller 460 of the master subsea node 240. The decision controller 460 receives data from the processor 433 of the system controller 430. Said data may relate to sensor data determined by at least one sensor associated with the master subsea node 240. The decision controller 460 also, via the system controller 430, receives input data, analysis data, or the like from at least one selected slave subsea node 250 and transmits a command signal, instruction data, or the like to said at least one selected slave subsea node 250. The selected slave subsea node 250 is the slave subsea node that is going to have its performance parameter modified in response to the command signal transmitted by the master subsea node 240. Aptly the decision controller 460, via the system controller 430 receives input data, analysis data, or the like from at least one master subsea node 240 and transmits instruction data to said at least one master subsea node 240. Alternatively the decision controller 460 may receive data directly without the system controller 430. The decision controller 460 determines whether a ’network decision’ or a ‘local decision’ performance parameter should be modified and if so generates a command signal that is transmitted via the system controller 430 to the selected slave subsea node / s 250. In other words the decision controller 460 coordinates the functions of at least one slave subsea node 250. The decision controller 460 evaluates the impact of varying a ‘network decision’ performance parameter of the slave subsea node 250 on the first subsea site 115, or alternatively on the second subsea site 116, on the third subsea site 117, or the like. The decision controller 460 proposes instructions and / or issues instructions to the processor 433 of the system controller. Said instructions may relate to operations carried out by the master subsea node 240 and / or operations carried out by any slave subsea node 250 connected to the master subsea node 240. The decision controller 460 may recognise and / or learn patterns in data it is provided with and create instructions accordingly. The operations of the decision controller 460 are described in more detail below. Aptly the decision controller 460 provides machine learning for its own local functionality. Aptly the decision controller 460 provides machine learning on all data from any networked subordinate unit (eg slave subsea node 250 or the like). Aptly the decision controller 460 supports in parameterisation of closed loop control. Aptly the decision controller 460 supports automated shutdown procedure. Aptly the decision controller 460 supports maintenance monitoring. The decision controller 460 includes a processor 463 for executing one or more instructions and a non-volatile storage medium 466. The processor 463 is a 32-bit microcontroller. Aptly the processor 463 is a 16-bit, a 32- bit, a 64-bit, or the like microcontroller or a 16-bit, a 32-bit, a 64-bit, or the like microprocessor. The non-volatile storage medium 466 is a flash storage. Aptly the non-volatile storage medium 466 is a disc storage, cloud storage, or the like.

[0094] It will be appreciated that the network switch 410 is in communication with the system controller 430, the communication interface 440, the subsea modem 450 and the decision controller 460. It will be appreciated that alternatively the instructions executed by the decision controller 460 may be executed by the system controller 430. It will be appreciated that in any embodiment the functions of the decision controller 460 may instead be functions of the system controller 430.

[0095] Figure 5 illustrates processing elements of the slave subsea node 250. It will be appreciated that Figure 5 is a simplified diagram and that the slave subsea node 250 may include many other components. It will be appreciated that the processing elements shown in Figure 5 are located in the SEM 360. Aptly the processing elements shown in Figure 5 may be located in the distribution unit 140. Aptly the processing elements shown in Figure 5 may be located in the manifold.

[0096] The slave subsea node 250 includes a network switch 510. The network switch 510 acts as a common interface to all internal components of the slave subsea node 250. In other words the network switch 510 is connected and thereby in communication with all internal components of the slave subsea node 250. Aptly the network switch 510 corresponds to the network switch 410. The slave subsea node 250 also includes a system controller 530. The system controller 530 manages functions of the slave subsea node 250. The system controller 530 thereby regulates operations of the subsea tree 320 and associated well 120 including any number of: controlling processing tasks, receiving instruction data, setting performance parameters, receiving input data from associated slave subsea node 250 sensors such as the SEM 360 sensors 340i ,2, transmitting input data, or the like. The performance parameters of the slave subsea node 250 may include: temperature, humidity, chemical composition, voltage, current, power, data rate, shock / impact, pH, pressure, valve actuation, regulator actuation, system activation, water injection rates, gas injection rates, DCV states, choke positions or the like. The data received from the master subsea node 240 includes a command signal or the like. Aptly the system controller 530 provides tree control and sensing function. Aptly the system controller 530 provides external interface management. Aptly the system controller 530 provides closed loop control function. Aptly the system controller 530 corresponds to the system controller 430. Aptly the system controller 530 manages functions of the distribution unit 140. The system controller 530 includes a processor 533 for executing one or more instructions and a non-volatile storage medium 536. The processor 533 is a 32-bit microcontroller. Aptly the processor 533 is a 16-bit, a 32-bit, a 64-bit, or the like microcontroller or a 16-bit, a 32-bit, a 64-bit, or the like microprocessor. The non-volatile storage medium 536 is a hard-disk drive. Aptly the non-volatile storage medium 536 is a flash storage, disc storage, or the like.

[0097] The slave subsea node 250 includes a subsea (S) modem 550. The S modem 550 is in communication with any combination of: at least one distribution unit 140, at least one SEM 360, at least one ROV, or the like. In other words the S modem 550 provides a communication link to other subsea components including the subordinate slave subsea node 250 and / or the master subsea node 240. The subordinate slave subsea nodes 250 are associated with the respective master subsea node 240. Aptly the S modem 550 corresponds to the S modem 450. It will be appreciated that the modem 550 includes at least one processor for executing one or more instructions (not shown) and optionally at least one non-volatile storage medium (not shown).

[0098] Figure 5 also illustrates a decision controller 560 of the slave subsea node 250. The decision controller 560 receives data from the processor 533 of the system controller 530. Said data may relate to sensor data determined by a sensor on the slave subsea node 250. Aptly the decision controller 560 corresponds to the decision controller 460. The system controller 530 also receives data from at least one master subsea node 240 and transmits data to said at least one master subsea node 240. Alternatively the decision controller 560 may receive and / or transmit data from / to at least one master subsea node 240. The decision controller 560 determines whether a ‘local decision’ performance parameter should be modified and if so generates a command signal that is transmitted to the system controller 530. The decision controller 560 may also receive a command signal from the master subsea node 240 that has been transmitted to the system controller 530. In other words the decision controller 560 coordinates the functions of the slave subsea node 250. The decision controller 560 proposes instructions and / or issues instructions to the processor 533 of the system controller. Said instructions may relate to operations carried out by the slave subsea node 250. The decision controller 560 may recognise and / or learn patterns in data it is provided with and create instructions accordingly. Aptly the decision controller 560 provides machine learning for its own local functionality. Aptly the decision controller 560 supports in parameterisation of closed loop control. Aptly the decision controller 560 supports automated shutdown procedure. Aptly the decision controller 560 supports maintenance monitoring. The decision controller 560 includes a processor 563 for executing one or more instructions and a non-volatile storage medium 566. The processor 563 is a 32-bit microcontroller. Aptly the processor 563 is a 16- bit, 32-bit, 64-bit, or the like microcontroller or microprocessor. The non-volatile storage medium 566 is a flash storage. Aptly the non-volatile storage medium 566 is a disc storage, cloud storage, or the like.

[0099] It will be appreciated that the network switch 510 is in communication with the system controller 530, the subsea modem 550 and the decision controller 560. It will be appreciated that alternatively the instructions executed by the decision controller 560 may be executed by the system controller 530. It will be appreciated that in any embodiment the functions of the decision controller 560 may instead be functions of the system controller 530.

[0100] Figure 6 illustrates a table 600 for determining whether the performance parameter is a local decision based on a predetermined condition. It will be appreciated that a local decision relates to a performance parameter that when modified only affects the subsea tree 320 associated with the SEM 360 (or only weakly effects other trees / equipment). In other words a local decision, where the performance parameter is varied at a given subsea tree 320, does not affect (or significantly affect) other subsea trees 320. In the table 600 the performance parameters are determined to make a local decision depending on the type of performance parameter that they are.

[0101] It will be appreciated that alternatively the predetermined condition may be a value limit or percentage limit of a performance parameter, whereby remaining under the value limit or percentage limit of the performance parameter corresponds to a local decision. In other words, where analysis data suggests that the performance parameter would be modified by at least the value limit or percentage limit, the performance parameter corresponds to a network decision. It will be appreciated that alternatively the predetermined condition may be a plurality of predetermined conditions whereby each of the conditions must be met for the performance parameter to be a local decision. Aptly a value limit or percentage limit is alternatively a value threshold or percentage threshold of a performance parameter.

[0102] Aptly, the Network decision may help determine a parameter that is going to change at a local level. For example, if Choke Position is going to be changed at local level, the decision and the value for the choke position will be done from the master at a “network decision”.

[0103] Aptly, a subsea node includes the local control list 600. Figure 7 illustrates a table 700 for determining whether the performance parameter is a network decision based on a predetermined characteristic. It will be appreciated that a network decision relates to a performance parameter that when modified at the subsea tree 320 associated with the SEM 360 affects other subsea trees 320. In the table 700 the performance parameters are determined to make a network decision depending on the type of performance parameter that they are.

[0104] Aptly, the Network decision may help determine a parameter that is going to change at a local level. For example, if Choke Position is going to be changed at local level, the decision and the value for the choke position will be done from the master at a “network decision”.

[0105] Aptly, a master subsea node includes the network control list 700.

[0106] In “manned” operation, a network decision may be a minor network decision or a major network decision. Aptly a minor network decision is a change to a performance parameter that is decided at the master subsea node 240. Aptly, a major network decision is a change to a performance parameter that is decided at the network master 210. If a network decision is not a minor network decision, then the decision may be classified as a major network decision. In other words when “minor network decision?” in table 700 is TRUE then changing a performance parameter may be characterised as a “minor decision”. When “minor network decision?” in table 700 is FALSE then changing a performance parameter may be characterised as a “major decision”. It will be appreciated that there may be other performance parameters not shown in Figure 7 that are network-level decisions.

[0107] It will be appreciated that alternatively the predetermined condition may be a value threshold or percentage threshold of a performance parameter, whereby exceeding the value threshold or percentage threshold of the performance parameter corresponds to a network decision. In other words, where analysis data suggests that the performance parameter would vary by at least the value limit or percentage limit, the performance parameter corresponds to a network decision. Aptly the predetermined condition may be a combination of performance parameters whereby the combination of performance parameters corresponds to a network decision. Aptly determining whether a performance parameter is a network decision may correspond to the opposite of the outcome of determining whether a performance parameter is a local decision. In other words in some embodiments a network decision performance parameter may be the opposite of a local decision performance parameter. Aptly a value threshold or percentage threshold is alternatively a value limit or percentage limit of a performance parameter. Figure 8 illustrates a method 800 of modifying performance parameters at a subsea node. The slave subsea node 250 is an example of the subsea node. The master subsea node 240 is also an example of the subsea node. It will be appreciated that the slave subsea node 250 may correspond to the SEM 360. That is to say that the method executed on the slave subsea node 250 is executed on the SEM 360. Alternatively the method executed by the slave subsea node 250 may be executed by a different physical device. A start step S805 represents normal operation of the slave subsea node 250 whereby the slave subsea node 250 is receiving input data from the sensor elements 340I,2 and / or input data associated with local performance of the subsea tree 320. In normal operation the performance parameters of the slave subsea node 250 have not yet been modified. The performance parameter is temperature, humidity, chemical composition, voltage, current, power, data rate, shock / impact, pH, pressure, valve actuation, regulator actuation, system activation, water injection rates, gas injection rates, DCV states, choke positions, valve positions, or the like.

[0108] A first receiving step S810 involves receiving, at the subsea node, respective input data from each sensor element. Input data are measured values of the at least one performance parameter by the at least one sensor 340I,2. That is to say each sensor 340I,2 provides values for each performance parameter that is measured.

[0109] A second receiving step S815 involves receiving, at the subsea node, a performance target. The performance target may be received from the network master node 210. The performance target is a preconfigured desired value of the performance parameter. It will be appreciated that the subsea node may receive more than one performance target.

[0110] An analysing step S820 involves analysing performance of the subsea node based on the at least one performance target and input data. The analysing step S820 thereby provides first analysis data. The first analysis data are determined at the subsea node in response to the input data from each of at least one sensor element. The analysing step S820 involves comparing the input data from the first receiving step S810 representing at least one real performance parameter with the one or more performance targets provided by the network master node 210. The analysing step S820 therefore provides how the one or more performance parameters should be modified. Aptly the analysing step S820 provides how well the subsea node is adhering to the one or more performance targets.

[0111] A determining step S825 involves determining whether the performance parameter satisfies a predetermined condition. In other words the determining step S825 involves determining whether modifying the performance parameter is a local decision. The predetermined condition is outlined in the table 600. Aptly the predetermined condition may be a value limit or percentage limit of a performance parameter, whereby remaining under the value limit or percentage limit of the performance parameter corresponds to a local decision. In other words, where the first analysis data suggests that the performance parameter would be modified by at least the value limit or percentage limit, the performance parameter corresponds to a network decision. It will be appreciated that alternatively the predetermined condition may be a plurality of predetermined conditions whereby each of the conditions must be met for the performance parameter to be a local decision. Aptly the determining step S825 involves determining whether adjusting the performance parameter is NOT a network decision. In other words the determining table illustrated in Figure 7 could be used alternatively, to determine whether adjusting the performance parameter is a network decision and therefore the opposite outcome to that determined by the determining step S825.

[0112] If the determining step S825 is TRUE - that is to say modifying the performance parameter is a local decision - then an actuating step S830 involves actuating a local change in a mode of operation thereby modifying the performance parameter. Modifying the performance parameter affects only the subsea node and corresponding subsea well 120 itself. Aptly, modifying the performance parameter does not affect other wells 120 in the subsea field 100. The actuating step S830 also involves reporting successful completion of actuating the local change in the mode of operation to the master subsea node 240. After the actuating step S830 is completed a finish stage 835 involves the method 800 ending.

[0113] If the determining step S825 is FALSE - that is to say adjusting the performance parameter is a network decision - then a providing step S840 involves providing, by the subsea node, data to the master subsea node 240. Aptly, the subsea node is determined as a slave subsea node 250. Aptly, a subordinate slave subsea node 250 associated with a respective master subsea node 240 provides data to the respective master subsea node 240. Aptly, modifying the performance parameter affects not just the slave subsea node 250 and corresponding subsea well 120 itself. That is to say modifying the performance parameter affects other wells 120 in the subsea field 100. Data provided by the slave subsea node 250 are analysis data from the analysing step S820. Aptly data provided by the slave subsea node 250 are alternatively input data from the receiving step S810. Aptly data provided by the slave subsea node 250 are alternatively both input data and analysis data. In effect there are at least three options: providing only input data from the slave subsea node 250 to the master subsea node 240; providing only first analysis data from the slave subsea node 250 to the master subsea node 240; or providing both input data and analysis data to the master subsea node 240.

[0114] It will be appreciated that such operation, whereby the master subsea node 240 determines, analyses and changes all network performance parameters, may occur during “unmanned” operation. Aptly, in “unmanned” operation all decisions regarding changing performance parameters are made subsea. Aptly, in unmanned operation the network master 210 may be a topside node that does not function as a network master. Either at the slave subsea node 250 if the decision is a local decision or at the master subsea node 240 if it is not a local decision. It will be appreciated that alternatively during so-called “manned” operation, in some embodiments data may be provided by the slave subsea node 250 to the network master 210 via the master subsea node 240, whereby performance parameters are determined topside at the network master 210, eg by a user, automated system or the like. In some embodiments during “manned” operation, analysis for how performance parameters may be changed is undertaken at the master subsea node 240, but the decision to enact the results of the analysis may only be issued topside eg by the network master 210.

[0115] A third receiving step S845 involves receiving, from the master subsea node 240, a command signal. The command signal is a change in a mode of operation provided by the master subsea node 240 to a selected slave subsea node. The selected slave subsea node is the slave subsea node that will have a performance parameter modified responsive to a decision / command signal issued by a master subsea node.

[0116] An actuating step S850 involves actuating a local change in a mode of operation thereby modifying the performance parameter in response to the command signal. Modifying the performance parameter here affects the slave subsea node 250 and corresponding subsea well 120 as well as other wells 120 in the subsea field 100. The actuating step S850 also involves reporting successful completion of actuating the local change in the mode of operation to the master subsea node 240. After the actuating step S850 is completed a finish stage 855 involves the method 800 ending.

[0117] It will be appreciated that the first receiving step S810 may be initiated by manual instruction from the network master node 210. Aptly the first receiving step S810 may be configured by the network master node 210 to be initiated upon receiving respective input data from at least one sensor element. Aptly the method 800 is repeated by manual instruction from the network master node 210. Aptly the method 800 is repeated a predetermined time period after the finish stage 835, 845. Aptly the method 800 is repeated upon occurrence of a predetermined event.

[0118] Figure 9 illustrates a method 900 of modifying performance parameters at the master subsea node 240. It will be appreciated that the master subsea node 240 may correspond to the distribution unit 140. Aptly, the method executed on the master subsea node 240 is executed at the distribution unit 140. Alternatively the method executed by the master subsea node 240 may be executed by a different physical device. It will be appreciated that the distribution unit 140 may be the manifold 140.

[0119] The present invention generally relates to two modes of operation “manned” and “unmanned”. Aptly, the two modes of operation are configurations of the network. “Manned” operation refers to operation of the subsea control system (such as illustrated by the schematic 200 of figure 2) including a network master / topside node. During “manned” operation some decisions regarding changing performance parameters are made topside. These decisions may be termed “major network decisions”. Other decisions regarding changing performance parameters are made at the master subsea node 240. These decisions may be termed “minor network decisions”. In “unmanned” operation, the subsea control system (such as illustrated by the schematic 200 of figure 2) may not include a network master. Aptly, during “unmanned” operation, all decisions regarding changing performance parameters are made subsea, eg by a slave subsea node, master subsea node, or the like.

[0120] A start step S905 represents normal operation of the master subsea node 240 whereby the master subsea node 240 is receiving input data from the sensor elements and / or input data associated with local performance of the distribution unit 140. In normal operation the performance parameters of the master subsea node 240 have not yet been modified. The performance parameter is temperature, humidity, chemical composition, voltage, current, power, data rate, shock / impact, pH, pressure, valve actuation, regulator actuation, system activation, water injection rates, gas injection rates, DCV states, choke positions, valve positions, or the like. Aptly the master subsea node 240 also performs a plurality of steps S805, S810, S815, S820 shown in Figure 8. In other words the master subsea node 240 may receive respective input data from each of at least one sensor element, analyse input data and actuate a local change in a mode of operation thereby modifying the performance parameter. A first receiving step S910 involves receiving, from at least one subordinate slave subsea node 250, respective data. Subordinate slave subsea nodes are nodes associated with a respective master subsea node. The respective data are analysis data provided by the analysing step S820 on the slave subsea node 250. That is to say analysis data are received by the master subsea node 240 from each of the slave subsea nodes 250 connected and managed by the master subsea node 240. The analysis data are determined at the slave subsea node 250 in response to the input data from each of at least one sensor element. Aptly the respective data are respective input data from each sensor element associated with the slave subsea node 250. Aptly, input data are measured values of the at least one performance parameter by the at least one sensor 340I,2 associated with the slave subsea node 250. That is to say each sensor 340I,2 provides values for each performance parameter that is measured.

[0121] A second receiving step S915 involves receiving, at the master subsea node 240, a performance target. The performance target may be received from the network master node 210. The performance target is a preconfigured desired value of the performance parameter. It will be appreciated that the master subsea node 240 may receive more than one performance target. It will be appreciated that the master subsea node 240 may receive a respective performance target from each slave subsea node 250 managed by the master subsea node 240.

[0122] A determining step S916 involves determining whether the performance parameter satisfies a predetermined characteristic. In other words the determining step S916 involves determining whether modifying the performance parameter is a minor network decision or a major network decision. The predetermined characteristic may be outlined in the table 700. Aptly the predetermined characteristic may be a value limit or percentage limit of a performance parameter, whereby remaining under the value limit or percentage limit of the performance parameter corresponds to a minor network decision. In some embodiments where the analysis data suggest that the performance parameter would be modified by at least the value limit or percentage limit, the performance parameter corresponds to a major network decision. It will be appreciated that alternatively the predetermined characteristic may be a plurality of predetermined characteristics whereby each of the characteristics must be met for the performance parameter to be a minor network decision.

[0123] If the determining step S916 is FALSE - that is to say changing the performance parameter is a major network decision and the master subsea node 250 is operating under “manned” operation, then a next step S917 involves providing, to the network master 210, data. The data may include input data from the master subsea node 240 and / or analysis data from the master subsea node 240 and / or input data from subordinate slave subsea nodes 250 and / or analysis data from subordinate slave subsea nodes 250. Responsive to instructions received from the network master 210, a next step S935 is initiated. It will be appreciated that in “unmanned” operation minor network decisions and major network decisions are both analysed and determined at the master subsea node 240. Aptly, in “unmanned” operation the outcome of the determining step S916 is in effect always TRUE.

[0124] If the determining step S916 is TRUE - that is to say changing the performance parameter is a minor network decision, then a next step is an analysing step S920 involving analysing performance of the slave subsea nodes 250 based on the at least one performance target and analysis data provided by each slave subsea node 250. The analysing step S920 thereby provides a second analysis data. That is to say the analysing step S920 involves comparing first analysis data from each slave subsea node 250 to consider the impact of actuating a local change in mode of operation of one slave subsea node 2503 on other slave subsea nodes 2504,5 or the like. Aptly, the analysing step S920 also involves comparing the outcome of first analysis data of each slave subsea node 250 on the one or more performance targets provided by the network master node 210.

[0125] An optional first reporting step S925 involves reporting the second analysis data to a lead master subsea node 240i. Where there is more than one master subsea node 240 in the communication network, one master subsea node 240i is delegated lead master subsea node 240i by the network master node 210. The remaining master subsea nodes 2402,3 are delegated second master subsea node 2402, third master subsea node 240s and so on. The master subsea nodes 240 are therefore in an order of hierarchy. The first reporting step S925 also involves the lead master subsea node 240i analysing the second analysis data of each master subsea node 240I,2,3, providing aggregate data and instructing all master subsea nodes 240 and their corresponding slave subsea nodes 250i.g accordingly.

[0126] An optional second reporting step S930 involves reporting aggregate data to the network master node 210 for approval. Aggregate data are compiled at a master subsea node 240 and then sent to the network master node 210. Usually aggregate data are transmitted by the lead master subsea node. That is to say the second reporting step S930 involves transmitting the second analysis data to the network master node 210 and waiting for a change in a mode of operation proposed by the second analysis data to be manually approved by the operator associated with the network master node 210. Aptly approval by the network master node 210 is automatic. It will be appreciated that aggregate data are data that are compiled at a master subsea node and then sent to a network master node. The network master node is usually the topside node and may be aligned with an MCS. The aggregate data indicate a proposed change to be made at at least one slave subsea node. This makes it easier for a topside operator to approve the proposed change. It will be appreciated that the second reporting step S930 may not occur in “unmanned” mode.

[0127] A providing step S935 involves providing, from the master subsea node 240, a command signal to a selected slave subsea node 250. The command signal is a change in a mode of operation. Aptly, the change in a mode of operation is proposed by the second analysis data. The selected slave subsea node is the slave subsea node that will have a performance parameter modified responsive to a decision / command signal issued by the master subsea node. That is to say the providing step S935 relates to commanding corresponding slave subsea nodes 250 according to the second analysis data thereby coordinating modifying the performance parameters of the slave subsea nodes 250. Aptly, the providing step S935 involves providing one or more command signals to the slave subsea node 250. Aptly, the providing step S935 involves providing one or more command signals to one or more slave subsea nodes 250 concurrently. It will be appreciated that in some embodiments, the providing step S935 may follow the providing step S917 involving receiving data from the network master 210. The data may include instructions that are received from the network master 210 relating to a “major” network decision that was determined in the determining step S916.

[0128] Alternatively, the providing step S935 may involve providing one or more command signals to one or more slave subsea nodes 250 sequentially. Sequentially here means providing one or more command signals to the first slave subsea node 250i, then after a first predetermined threshold providing one or more command signals to the second slave subsea node 2502, then after a second predetermined threshold providing one or more command signals to the third slave subsea node 250a and so on. The first predetermined threshold corresponds to a predetermined delay after receiving, from the first slave subsea node 250i, verification that the one or more command signals provided to the first slave subsea node 250i have been successfully implemented. Similarly, the second predetermined threshold corresponds to a predetermined delay after receiving, from the second slave subsea node 2502, a verification that the one or more command signals provided to the second slave subsea node 2502 have been successfully implemented, and so on for a third, fourth or greater predetermined threshold. The verification may include confirming that the new performance parameter values broadly or exactly match predicted performance parameter values. Therefore the alternative providing step S935 provides a slow phased change across the communication network.

[0129] An optional third reporting step S940 involves reporting, to the network master node 210, that the command signal has been provided to the respective slave subsea nodes 250. In other words the third reporting step S940 includes transmitting data via the umbilical 135 to the MCS 132 where the data confirms that the command signal has been provided by the distribution unit 140.

[0130] After the providing step S935 and optional third reporting step S940, a finish stage 945 involves the method 900 ending.

[0131] It will be appreciated that the first receiving step S910 may be initiated by manual instruction from the network master node 210. Aptly the first receiving step S910 may be configured by the network master node 210 to be initiated upon receiving respective data from at least one slave subsea node. Aptly the first receiving step S910 may be configured by the network master node 210 to be initiated upon receiving respective data from at least one sensor element. Aptly the method 900 is repeated by manual instruction from the network master node 210. Aptly the method 900 is repeated a predetermined time period after the finish step S945. Aptly the method 900 is repeated upon occurrence of a predetermined event. Aptly the method 900 is repeated upon. It will be appreciated that alternatively the method 800 and the method 900 may be implemented by any subsea node 240, 250.

[0132] Figure 10 illustrates a schematic 1000 of an alternative subsea control system including three subsea sites 1010, 1011 , 1012, the network master node 210 and umbilicals 1354-6. It will be appreciated that each subsea site 1010, 1011 , 1012 is a geographical region below the surface 110 of a body of water (eg a sea, lake, river, or the like). It will be appreciated that the network master node 210 is a node that corresponds to the MCS 132.

[0133] A fourth subsea site 1010 includes a fourth master subsea node 2404 and five subordinate slave subsea nodes 250 -i4. The fourth master subsea node 2404 includes a fourth decision controller 4604. A fifth subsea site 1012 includes a fifth master subsea node 240s. The fifth master subsea node 240s includes a fifth decision controller 460s. A sixth subsea site 1012 includes a sixth master subsea node 240e and five subordinate slave subsea nodes 250IS-22. The sixth master subsea node 240e includes a sixth decision controller 460e.The master subsea nodes 2404-6 correspond to respective distribution units 140. It will be appreciated that the distribution unit 140 may be a manifold 140. The slave subsea nodes 250 -22 correspond to respective subsea trees 320. It will be appreciated that the subsea tree 320 may be a Christmas tree.

[0134] During operation, the master subsea nodes 2404-6 implement the method 900 outlined in Figure 9. The slave subsea nodes 250 -22 implement the method 800 outlined in Figure 8. The fourth master subsea node 2404 shown in Figure 10 is delegated ‘lead’ master subsea node 2404. The sixth master subsea node 240e is delegated ‘secondary’ master subsea node 240e. The fifth master subsea node 240s is delegated ‘tertiary’ master subsea node 240s. Therefore, when the method 900 is implemented by the master subsea nodes 2404-6, the first reporting step S925 involves first analysis data from the secondary master subsea node 240e and the tertiary master subsea node 240s being reported to the lead master subsea node 2404. According to the optional second reporting step S930, aggregate data compiled at the lead master subsea node from the lead, secondary, and tertiary master subsea nodes 240, are reported to the network master node 210 for approval. After approval is received from the network master node 210, one or more command signals are generated by the master subsea nodes 2404-6, the one or more command signals are provided to the subordinate slave subsea nodes 240 -22 sequentially as outlined in the alternative providing step S935.

[0135] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to” and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0136] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and / or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel one, or novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0137] The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS:

1. A method of modifying at least one performance parameter at a subsea location, comprising the steps of: at a first subsea node, receiving respective input data from each of at least one sensor element; via a processor element at the first subsea node, determining if the input data is associated with a respective performance parameter that satisfies a predetermined first condition; and if the respective performance parameter satisfies the predetermined first condition, via the processor element at the first subsea node, determining if the performance parameter should be modified and if so actuating a local change in a mode of operation thereby modifying the performance parameter.

2. The method as claimed in claim 1 , further comprising: if the respective performance parameter does not satisfy the predetermined first condition, designating the first subsea node as a first slave subsea node; providing the input data and / or analysis data, determined at the first slave subsea node and responsive to the input data, to a master processor element at a master subsea node, remote from said first slave subsea node, that is connected via a first communication link to the first slave subsea node and, via at least one respective further communication link, to a respective at least one further slave subsea node; and receiving a command signal indicating that the performance parameter should be modified via the first communication link at the first slave subsea node and, at the first slave subsea node in response to the command signal, actuating a local change in a mode of operation thereby modifying the performance parameter.

3. The method as claimed in any preceding claim, further comprising: determining if the respective performance parameter satisfies the predetermined first condition by determining if the performance parameter is on an allowed local control list that identifies performance parameters that can be modified locally.

4. The method as claimed in any preceding claim, further comprising:determining if the performance parameter should be modified by determining if a sensed value for the performance parameter in the input data reaches or falls below a respective threshold value.

5. The method as claimed in any one of claims 1 to 3, further comprising: determining if the performance parameter should be modified by determining if a trend in change of a value for the performance parameter in the input data indicates that the sensed value will reach or fall below a respective threshold value in a pre-set future time period and modifying the performance parameter prior to the sensed value reaching or falling below the respective threshold value.

6. The method as claimed in any preceding claim, further comprising: actuating the local change by generating at least one command signal at the subsea node and, providing the command signal to at least one subsea auxiliary equipment element proximate to the slave subsea node and, responsive to the command signal, varying operation of the auxiliary equipment.

7. The method as claimed in claim 2 or any one of claims 3 to 5, when dependent upon claim 2, further comprising: actuating the local change by receiving at least one command signal, from a master subsea node, at the slave subsea node and providing the command signal to at least one subsea auxiliary equipment element proximate to the slave subsea node and, responsive to the command signal, varying operation of the auxiliary equipment.

8. The method as claimed in claim 6 or claim 7, further comprising: the auxiliary equipment element comprises a subsea actuator, that optionally is a hydraulic or pneumatic or electric actuator, or a subsea valve that optionally is a control or isolation valve.

9. A method of modifying at least one performance parameter at a subsea location, comprising the steps of: at a master subsea node, receiving respective input data from each of at least one sensor element at a respective at least one slave subsea node; determining if the respective input data is associated with a respective performance parameter that satisfies a predetermined first characteristic;if the respective performance parameter does not satisfy the predetermined first characteristic, providing the respective input data to a topside node or if the respective performance parameter satisfies the predetermined first characteristic, via a master processor element at the master subsea node, responsive to at least the respective input data, determining if a performance parameter associated with a selected slave subsea node should be modified; and responsive to determining if the performance parameter should be modified, providing a command signal indicating that the performance parameter should be modified from the master subsea node to at least said a selected subsea node.

10. The method as claimed in claim 9, further comprising: providing the input data to the master processor element via a first communication link between the master subsea node and said a selected slave subsea node; and providing the command signal via the first communication link.

11. The method as claimed in claim 9 or claim 10, further comprising: at the master processor at the master subsea node, prior to generating the command signal, receiving input data from one or more sensors of a plurality of slave subsea nodes; determining how local changes in modes of operation at the plurality of slave subsea nodes are advisable to balance performance across multiple local sites of a field site; and responsive to determining advisable changes to balance performance, generating a plurality of command signals and respectively providing each of those generated command signals to a plurality of slave subsea nodes.

12. The method as claimed in any one of claims 9 to 11 , further comprising: determining if the performance parameter should be modified by determining if a sensed value for the performance parameter in the input data reaches or falls below a respective threshold value.

13. The method as claimed in any one of claims 9 to 11 , further comprising: determining if the performance parameter should be modified by determining if a trend in change of a value for the performance parameter in the input data indicatesthat the sensed value will reach or fall below a respective threshold value in a pre-set future time period and modifying the performance parameter prior to the sensed value reaching or falling below the respective threshold value.

14. The method as claimed in any one of claims 9 to 13, further comprising: at the master subsea node, receiving performance target data from a topside node and determining if the performance parameter associated with at least one slave subsea node should be modified responsive to the performance target data and said at least said input data.

15. The method as claimed in claim 14, further comprising: receiving the performance target data at the master subsea node via a further communication link, comprising a communication link provided via an umbilical, between the master subsea node and a topside control station.

16. The method as claimed in claim 14 or claim 15, further comprising: prior to providing said a command signal, providing aggregate data, comprising data responsive to respective input data received at the master subsea node from a plurality of slave subsea nodes, to the topside node; and responsive to an approval signal received at the master subsea node from the topside node, providing said a command signal to at least the selected slave subsea node.

17. The method as claimed in claim 16, further comprising: repeatedly providing aggregate data to the topside node with proposal data that comprises data, determined at the master subsea node, indicating a proposed local change in a mode of operation at at least one subordinate slave subsea node subordinate to the master subsea node; receiving, at the master subsea node, one-by-one, a respective approval signal from the topside node; and modifying respective performance parameters at said at least one subordinate slave subsea node over a period of time responsive to the approval signals received one-by-one at the master subsea node.

18. Apparatus for modifying at least one performance parameter at a subsea location, comprising: a plurality of slave subsea nodes each receiving respective input data from each of at least one sensor element and each comprising a respective at least one slave processor element for determining if the corresponding input data is associated with a respective performance parameter that satisfies a predetermined first condition; and at least one master subsea node each connected to a respective at least one subordinate slave subsea node and disposed to receive respective input data from each subordinate slave subsea node; wherein the master subsea node comprises a master processor element for determining if a respective performance parameter should be modified if the slave processor element determines that the input data is not associated with a respective performance parameter that satisfies the predetermined first condition.

19. The apparatus as claimed in claim 18, further comprising: each slave subsea node is connected via a respective first communication link to a respective master subsea node to which said each slave subsea node is subordinate; and at least one master subsea node is connected to a topside node via a further communication link provided via an umbilical.

20. The apparatus as claimed in claim 18 or claim 19, further comprising: each subsea node comprises an allowed local control list accessible to a respective slave processor element, said local control list comprising data indicating performance parameters that can be modified locally at an associated slave subsea node and / or each master subsea node comprises an allowed network control list accessible to a respective master processor element, said network control list comprising data indicating performance parameters that should be modified at the master subsea node.

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