Data storage and provision

Abstract

A subsea module locatable at a subsea location, a method of storing data at the subsea module, and a method of providing performance related data to a topside node of a communication network are disclosed. The method of storing data at a subsea module comprises the steps of: determining that at least one predetermined event has occurred and a respective time of occurrence; at a first sampling rate and at least subsequent to said time of occurrence, repeatedly determining a value for each of at least one performance parameter associated with a subsea module at a subsea location; for each occurrence, storing key record values indicative of determined values for said performance parameters determined at the first sampling rate for a period of time, comprising a key event recording period; and determining said a value at the first sampling rate repeatedly at a greater frequency than an effective sampling rate of determining performance parameter values associated with uneventful record values that are stored and that are indicative of determined values outside of a key event recording period.

Description

[0001] DATA STORAGE AND PROVISION

[0002] The present invention relates to a method and apparatus for storing and providing data. In particular, but not exclusively, the present invention relates to controlling the monitoring and recording of data based on determining that one or more predetermined events have occurred to provide high information content around when key events occur and less content heavy data during uneventful periods.

[0003] 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.

[0004] 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. 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 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.

[0005] 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 or not captured. 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. With prior art solutions, debugging analysis is often retrospective and in some cases the anomalous behaviour is no longer visible.

[0006] It is an aim of the present invention to at least partly mitigate one or more of the above- mentioned problems. It is an aim of certain embodiments of the present invention to automatically provide a higher rate of measurement parameters at or around a time when a predetermined event is detected.

[0007] It is an aim of certain embodiments of the present invention to automatically provide a higher quantity of data when a predetermined event has occurred and / or to record said higher quantity of data for a preconfigured period of time.

[0008] It is an aim of certain embodiments of the present invention to automatically adjust a sampling rate associated with a performance parameter based on the occurrence of predetermined events.

[0009] It is an aim of certain embodiments of the present invention to automatically adjust a sampling rate at which data associated with a performance parameter is stored, based on the occurrence of predetermined events.

[0010] It is an aim of certain embodiments of the present invention to provide a method for optimising the provision of sensor data values of variable frequency and / or detail over a limited bandwidth.

[0011] It is an aim of certain embodiments of the present invention to provide a method for optimising the recording of sensor data values of variable frequency and / or detail to a limited data storage medium.

[0012] It is an aim of certain embodiments of the present invention to provide apparatus for determining the verbosity of data values to be stored on non-volatile storage.

[0013] 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 an issue associated with a subsea well or a subsea tree.

[0014] According to a first aspect of the present invention, there is provided a method of storing data at a subsea module, comprising the steps of: determining that at least one predetermined event has occurred and a respective time of occurrence; at a first sampling rate and at least subsequent to said time of occurrence, repeatedly determining a value for each of at least one performance parameter associated with a subsea module at a subsea location; for each occurrence, storing key record values indicative of determined values for said performance parameters determined at the first sampling rate for a period of time, comprising a key event recording period; and determining said a value at the first sampling rate repeatedly at a greater frequency than an effective sampling rate of determining performance parameter values associated with uneventful record values that are stored and that are indicative of determined values outside of a key event recording period.

[0015] Aptly, the method further comprises: determining said a value at the first sampling rate at all times and storing respective key record values for each determined value associated with a period of time before and after the time of occurrence.

[0016] Aptly, the method further comprises: repeatedly averaging a plurality of determined values and storing respective averaged values as uneventful record values during periods of time outside of a key event recording period.

[0017] Aptly, the method further comprises: determining each said a value at a normal sampling frequency less than the first sampling rate and corresponding to the effective sampling rate until a predetermined event is determined to have occurred and then determining each said a value at the first sampling rate until a predetermined threshold is satisfied.

[0018] Aptly, the method further comprises: the predetermined threshold is elapse of a predetermined time period or receipt of confirmation that an event has ceased or receipt of an indication that an operator has indicated that the first sampling rate determination is to cease and sampling at the normal sampling frequency is to resume.

[0019] Aptly, the method further comprises: determining that a predetermined event has occurred subsequent to a preceding uneventful period set apart in time by a predetermined period of time from said time of occurrence.

[0020] Aptly, the method further comprises: determining that the predetermined event has occurred at at least one subsea module that optionally comprises at least one SEM or at least one SCM.

[0021] Aptly, the method further comprises: repeatedly determining determined values immediately after said time of occurrence or immediately after a delay time has expired subsequent to said time of occurrence.

[0022] Aptly, the method further comprises: 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.

[0023] Aptly, the method further comprises: the one or more connections may be wired connections, wireless connections, or the like.

[0024] Aptly, the method further comprises: a node is a virtual point in a communication network.

[0025] Aptly, the method further comprises: a network master node is a node that is associated with a physical location on / at the surface of a body of water.

[0026] Aptly, the method further comprises: 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.

[0027] Aptly, the method further comprises: a subsea node is associated with a physical location that is vertically offset by 1 m, 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 1 m, 10m, 500m, 10km or more from the neighbouring subsea node.

[0028] Aptly, the method further comprises: a network master node is a node that is physically located on / at the surface of a body of water.

[0029] Aptly, the method further comprises: 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.

[0030] Aptly, the method further comprises: a network master node is an FPSO.

[0031] Aptly, the method further comprises: a network master node is a surface platform.

[0032] Aptly, the method further comprises: a network master node is a topside component.

[0033] Aptly, the method further comprises: a subsea node is an SCM, SEM, distribution unit, manifold, PCDM, OEM, subsea tree, or the like.

[0034] Aptly, the method further comprises: a key event recording period is a recording period where a verbose mode of an operating system is enabled.

[0035] Aptly, the method further comprises: a sampling rate is a polling rate.

[0036] Aptly, the method further comprises: a sampling rate is a rate at which values provided by a sensor are read. Aptly, the method further comprises: a sampling rate is a rate at which values of a performance parameter provided from a sensor are retrieved by a processor element.

[0037] According to a second aspect of the present invention there is provided a method of providing performance related data to a topside node of a communication network, comprising the steps of: at a subsea module disposed at a subsea location, storing key record values associated with occurrence of a key event and storing uneventful record values for each period of time not associated with occurrence of a key event; and providing key event record values and uneventful record values as performance related data from the subsea module to a topside node of a communication network thereby providing key record values associated with a more frequent sampling rate than the uneventful record values.

[0038] Aptly, the method further comprises: at the subsea module, determining a value for each of at least one performance parameter associated with the subsea module and storing key record values indicative of determined values determined at a first sampling rate for a period of time comprising a key event recording period.

[0039] Aptly, the method further comprises: at the subsea module, determining a value for each of at least one performance parameter at a first sampling rate repeatedly at a greater frequency than an effective sampling rate of determining performance parameter values associated with uneventful record values that are stored at the subsea module and that are indicative of determined values outside of a key event recording period.

[0040] Aptly, the method further comprises: providing performance related data to the topside node for each period of time, comprising a key event recording period, associated with each occurrence of a respective predetermined event.

[0041] Aptly, the method further comprises: providing an operator at a user interface (III) at a topside location associated with the topside node with the performance related data; and via the operator III, selecting an action and providing an instruction signal to the subsea module responsive thereto.

[0042] Aptly, the method further comprises: providing the key record values as detailed data that is more detailed per unit time than the uneventful record values.

[0043] Aptly, the method further comprises: transferring key record values from the subsea module to the topside node as transfer data having a greater information content than transfer data provided by uneventful record values transferred from the subsea module to the topside node.

[0044] Aptly, the method further comprises: 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.

[0045] Aptly, the method further comprises: the one or more connections may be wired connections, wireless connections, or the like.

[0046] Aptly, the method further comprises: a node is a virtual point in a communication network.

[0047] Aptly, the method further comprises: a network master node is a node that is associated with a physical location on / at the surface of a body of water.

[0048] Aptly, the method further comprises: 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. Aptly, the method further comprises: a subsea node is associated with a physical location that is vertically offset by 1 m, 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 1 m, 10m, 500m, 10km or more from the neighbouring subsea node.

[0049] Aptly, the method further comprises: a network master node is a node that is physically located on / at the surface of a body of water.

[0050] Aptly, the method further comprises: 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.

[0051] Aptly, the method further comprises: a network master node is an FPSO.

[0052] Aptly, the method further comprises: a network master node is a surface platform.

[0053] Aptly, the method further comprises: a network master node is a topside component.

[0054] Aptly, the method further comprises: a subsea node is an SCM, SEM, distribution unit, manifold, PCDM, OEM, subsea tree, or the like.

[0055] Aptly, the method further comprises: a key event recording period is a recording period where a verbose mode of an operating system is enabled.

[0056] Aptly, the method further comprises: a sampling rate is a polling rate.

[0057] Aptly, the method further comprises: a sampling rate is a rate at which values provided by a sensor are read.

[0058] Aptly, the method further comprises: a sampling rate is a rate at which values of a performance parameter provided from a sensor are retrieved by a processor element.

[0059] According to a third aspect of the present invention there is provided a subsea module locatable at a subsea location, comprising: a first processor element for receiving sensor data from at least one sensor and / or executing a test procedure at a subsea module; a further processor element responsive to a determination that at least one predetermined event has occurred, for storing the key record values in a first data store and uneventful record values in a further data store, said key record values indicative of determined values for at least one performance parameter determined at a first sampling rate that has a more frequent frequency than an effective sampling rate of determining performance parameter values associated with the uneventful record values.

[0060] Aptly, the subsea module further comprises: the first data store and the further data store are distinct and separate data stores or are respective partitioned areas of a common data store.

[0061] Aptly, the subsea module further comprises: the further processor element comprises an event detector that detects if a predetermined event has occurred and a respective time of occurrence for each event.

[0062] Aptly, the subsea module further comprises: the further processor element is spaced apart from a primary processor element of an SEM or SCM.

[0063] Aptly, the subsea module further comprises: the further processor element includes an initiation signal generator that generates an initiation signal to provide greater information content from the first processor element and is disposed to selectively provide the initiation signal to the further processor element. 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.

[0064] Aptly, the one or more connections may be wired connections, wireless connections, or the like.

[0065] Aptly, a node is a virtual point in a communication network.

[0066] Aptly, a topside node is a node that is associated with a physical location on / at the surface of a body of water.

[0067] 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.

[0068] 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.

[0069] Aptly, a topside node is a node that is physically located on / at the surface of a body of water.

[0070] 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.

[0071] Aptly, a topside node is an FPSO.

[0072] Aptly, a topside node is a surface platform.

[0073] Aptly, a topside node is a topside component.

[0074] Aptly, a subsea node is an SCM, SEM, distribution unit, manifold, PCDM, CEM, subsea tree, or the like. Aptly a key event recording period is a recording period where a verbose mode of an operating system is enabled.

[0075] Aptly a sampling rate is a polling rate.

[0076] Aptly a sampling rate is a rate at which values provided by a sensor are read.

[0077] Aptly a sampling rate is a rate at which values of a performance parameter provided from a sensor are retrieved by a processor element.

[0078] Aptly, a network master node is a topside node and may be aligned with a master control system (MCS).

[0079] Certain embodiments of the present invention provide apparatus that stores measurement parameters, where an associated resolution and time frequency of stored measurement parameters is selected according to the detection of a predetermined event. This has the advantage of preserving more information during times which are likely to be of most interest to an operator.

[0080] Certain embodiments of the present invention provide a method for automatically using a high information content mode to continuously log until a fault is cleared. The high information content mode can be a “verbose” mode.

[0081] Certain embodiments of the present invention provide a method for automatically using a high sampling rate mode to continuously log until an instruction to stop by the user.

[0082] Certain embodiments of the present invention provide a method for automatically using a high sampling rate mode to log for a specific period of time that can be configured by the user.

[0083] Certain embodiments of the present invention provide apparatus that logs only specific functions based on a Built In Test (BIT) failure I anomaly detection.

[0084] Certain embodiments of the present invention provide statistics of the individual faults / anomalies to provide how often said individual faults / anomalies occur and clear. Certain embodiments of the present invention provide, in a limited bandwidth environment, immediate operator consumption for only an increase in pertinent data distributed topside.

[0085] Certain embodiments of the present invention provide apparatus that stores values for measurement parameters in a high sampling rate mode for a predetermined period of time.

[0086] Certain embodiments of the present invention provide a method for recognising an event, eg periodical Built It Test (BIT) failure, anomaly detection, shock / vibration thresholds.

[0087] Certain embodiments of the present invention provide the ability to help maximise subsea processing power and to increase the fidelity of production and sensor data automatically on event detection. This may provide a benefit to the operator for fault finding / debugging situations as well as oil field maintenance. Not only can the present invention help increase the rate of data logged subsea, an increase in pertinent data could automatically be sent topside, to aid the operator to make better decisions regarding well management. At the same time the lower priority data in that situation is still being gathered locally subsea for use later if required.

[0088] Certain embodiments of the present invention provide apparatus that temporarily stores values for measurement parameters of a sensor in a verbose mode for a predetermined period of time before averaging verbose data (eg measurement parameters) over a number of time periods for long term storage. This has the advantage of reducing the data storage required for measurement parameters that are unlikely to be of interest by lowering the effective sampling rate of the sensor.

[0089] Certain embodiments of the present invention provide apparatus that temporarily stores values for measurement parameters in a verbose mode for a predetermined period of time before permanently storing verbose measurement parameters, if a predetermined event has recently since occurred. In other words, in certain embodiments, measurement parameters are monitored in a verbose mode by default and temporarily stored for recall if a predetermined event subsequently occurs.

[0090] Certain embodiments of the present invention monitor regular internal Built In Test (BIT) fault flags and identify a BIT fault as a predetermined event. Certain embodiments of the present invention provide a method for recalling values for frequently measured parameters captured by one or more sensors that occurred soon before a predetermined event.

[0091] Certain embodiments of the present invention provide a method for recalling verbose measurement parameters captured by one or more sensors that occurred soon before an anomaly was detected, so that measurement parameters leading up to the anomaly are available in verbose mode.

[0092] Certain embodiments of the present invention provide a method that varies a sampling rate of measurement parameters from one or more sensors based on the detection of one or more predetermined events.

[0093] Certain embodiments of the present invention provide a method that varies a recording rate of measurement parameters from one or more sensors based on the detection of one or more predetermined events.

[0094] Certain embodiments of the present invention provide the operation with additional information that aids them to make better and quicker decisions around faults and production issues.

[0095] Certain embodiments of the present invention provide efficient use of subsea hardware storage by only logging at a higher fidelity when required, the rest of the time the hardware can log at a rate of 1 Hz.

[0096] 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.

[0097] Embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

[0098] Figure 1 illustrates a subsea field with multiple installation wells;

[0099] Figure 2 illustrates a schematic diagram of a subsea control system;

[0100] Figure 3 illustrates a subsea well configuration; Figure 4 illustrates a method of storing data using a data flow diagram;

[0101] Figure 5 illustrates a method of storing data using a timeline;

[0102] Figure 6 illustrates a method of storing data;

[0103] Figure 7 illustrates an alternative method of storing data using a data flow diagram;

[0104] Figure 8 illustrates an alternative method of storing data using a timeline;

[0105] Figure 9 illustrates an alternative method of storing data; and

[0106] Figure 10 illustrates an alternative subsea well configuration.

[0107] In the drawings like reference numerals refer to like parts.

[0108] 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 alternatively other field architectures may be used. 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.

[0109] 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.

[0110] The FPSO 130 is connected via a first umbilical 135i to a 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.

[0111] 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. 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.

[0112] Figure 2 illustrates a subsea control system diagram 200 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.

[0113] The communication network is an interconnected group of nodes that can communicate with each other 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 1 m, 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.

[0114] Figure 2 illustrates use of a network master 210. The illustrated network master 210 is located topside. The network master 210 is located on the FPSO 130. It will be appreciated that the FPSO 130 may alternatively be a floating platform, a land platform, or the like. It will be appreciated that the network master 210 is associated with 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 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 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 210 could alternatively communicate with and / or manage one, two, four, or more sub-networks 220. Communication of data between the network master 210 and any sub-network 220 is facilitated by the umbilical 135I-3. 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, DSL, other wired connection, wireless connection or the like. The first umbilical 135i connects the network master 210 to a first sub-network master 240i. The second umbilical 1352 connects the network master 210 to a second sub-network master 2402. The third umbilical 135s connects the network master 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, other wired connection, wireless connection or the like. 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.

[0115] 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 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 210 and sub-network masters 240I-3. Aptly there is a tree / star network between the network master 210 and sub-network masters 240I-3. There is a tree / star sub-network between a given subnetwork 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.

[0116] 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’. 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. 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 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.

[0117] 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 a performance parameter monitored by a sensor 340 as 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 sensor 3402 may be located inside the SCM 350. In some embodiments, a wired connection may be used to connect the sensors 340I,2 to 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 sensors 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 340 data. 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.

[0118] The SEM 360 includes a first processor 370 for executing one or more instructions, a nonvolatile storage medium 380 (e.g. a hard disk drive, flash storage, or the like), and a second processor 390 for executing one or more instructions. The second processor 390 may be an EDGE PC. Alternatively the first processor 370, storage 380 and second processor 390 may be combined into one unit. It will be appreciated that alternatively there may be at least two non-volatile storage media 380. The first processor 370 is a 32-bit microcontroller, although it will be appreciated that alternatively the first processor 370 could be a 16-bit, 32-bit, 64-bit, or the like microcontroller or microprocessor. The first processor 370 provides the control functionality of the SEM 360. In other words, based on information inputted into the SEM 360, the first processor 370 executes instructions which affect the functions of the subsea tree 320. The first processor 370 has access to volatile memory such as Random Access Memory (RAM) (not shown). Aptly the volatile memory is located in the first processor 370. The first processor 370 is connected to the storage media 380. Instructions may be recalled from the storage media 380 and executed on the first processor 370. The second processor 390 primarily manages sensor data from the sensors 340. The second processor 390 receives measurement data from the sensors 340 and other data such as Built In Test (BIT) status from the first processor 370. Sensor data from the sensors 340 are at times stored on the storage media 380, as will be explained in more detail in respect of the succeeding figures described below. It will be appreciated that in alternative embodiments, the SEM 360 has only the first processor 370, whereby the functions of the second processor 390 are carried out on the first processor 370. In other words, in some embodiments, the first processor 370 and second processor 390 are combined into one processor.

[0119] Figure 4 illustrates a function of the second processor 390 using a data flow diagram. As shown in Figure 4 and discussed with respect to Figure 3, there is a data link between the first processor 370 and the second processor 390. The data link between the first processor 370 and the second processor 390 is facilitated by an ethernet connection. Aptly, the data link between the first processor 370 and the second processor 390 is alternatively facilitated by a fibre connection, cable connection, wireless connection, RS485, I2C, internal connection or the like. Periodically, at predetermined time intervals, the first processor 370 runs a Built In Test (BIT). The BIT evaluates the normal functioning of the SEM 360, subsea tree 320 and associated components such as valves 330, sensors 340, network connections and the like. The BIT thereby checks that the subsea tree 320 is functioning correctly. The BIT returns a BIT error status of either TRUE (1 in binary) or FALSE (0 in binary). Aptly the BIT status is alternatively either FAIL, corresponding to a 0 in binary, or PASS, corresponding to a 1 in binary. It will be appreciated that in some embodiments the BIT may return more data including details of any problems identified during the test.

[0120] Periodically, at predetermined time intervals, the second processor 390 checks the BIT status and / or a predetermined event status at a first step S410. The predetermined event status may refer to the occurrence of a predetermined event at the present time, whereby if the predetermined event is occurring then the predetermined event status is set to TRUE. If the predetermined event is not occurring then the predetermined event status is set to FALSE. In some embodiments, if the predetermined event occurs then the predetermined event status is set TRUE and will remain TRUE until the predetermined event status is reset (ie manually set to FALSE). It will be appreciated that there may be multiple predetermined event statuses to be checked. The predetermined event may refer to a value of a measurement parameter of a performance parameter monitored by the sensor 340 exceeding a predetermined value. Aptly, the predetermined event may refer to a value of the performance parameter monitored by the sensor 340 falling below a predetermined value. Aptly, the predetermined event may refer to multiple values of performance parameters monitored by multiple sensors 340 falling below or exceeding predetermined values in any combination concurrently. Aptly, the predetermined event may refer to certain data received by the subsea tree 320 or associated SEMS 360.

[0121] If the BIT error status and / or predetermined event status is FALSE then a next step S420 follows the first step S410. In the step S420, a standard logging mode is maintained and a normal sampling rate at which the sensor 340 monitors the performance parameter and the determined value of the performance parameter is read by the first processor 370 is unchanged. In other words in the step S420 the sampling / polling rate of the sensor 340 is equal to a normal sampling frequency set prior to the BIT error statu s / p red etermined event check step S410. The normal sampling frequency of the sensor 340 is 1 Hz. Aptly the normal sampling frequency of the sensor 340 is less than 1 Hz. Aptly the normal sampling frequency of the sensor 340 is 2Hz, 3Hz, 4Hz or any other value greater than 1 Hz. It will be appreciated that alternatively, one or more of a total number of sensors 340 may have a sampling rate equal to the normal sampling frequency. In a next step S425 the determined value for the performance parameter at the sampling rate corresponding to the normal sampling frequency is stored in the storage medium 380. Aptly the determined value for said performance parameter is stored for 1 hour. Aptly the determined value for said performance parameter is stored for two, three, four, six, eight, ten, twelve, or more hours. Aptly the determined value for said performance parameter is stored for one, two, three, four, six, eight, ten, twelve, or more days. Aptly the determined value for said performance parameter is stored until a command is issued to delete the determined value. It will be appreciated that the normal sampling rate may be an effective sampling rate. The effective sampling rate may be associated with a rate of determining performance parameter values associated with uneventful record values.

[0122] If the BIT error status and / or predetermined event status is TRUE then a next step S430 follows the first step S410. In the next step S430 a verbose logging mode is initiated for a predetermined period of time and a time of occurrence is recorded. The predetermined period of time is 20 minutes, although it will be appreciated that alternatively the predetermined period of time may be 5 minutes, 10 minutes, 30 minutes, or the like. In some embodiments the verbose logging mode is deactivated by an instruction from the MCS 132. In some embodiments the verbose logging mode is deactivated when predetermined criteria are met. The predetermined criteria could include threshold sensor values or the like. In the next step S430 the second processor 390 instructs the first processor 370 to gather sensor data at an increased sampling frequency relative to the normal sampling frequency. In other words, the sampling rate at which the sensor 340 monitors the performance parameter and determined values of performance parameters are read by the first processor 370 is equal to the increased sampling frequency. The increased sampling frequency may be referred to as a first sampling rate. The increased sampling / polling frequency of the sensor 340 is 5Hz. Aptly the increased sampling frequency of the sensor 340 is less than 5Hz. Aptly the increased sampling frequency of the sensor 340 is 6Hz, 7Hz, 8Hz or any other value greater than 5Hz. It will be appreciated that alternatively, one or more of a total number of sensors 340 may have a sampling rate equal to the increased sampling frequency. In other words it is possible for one or more sensors 340 to be read at the increased sampling frequency whilst the remaining sensors 340 are read at the normal sampling frequency. Aptly, there may be more than one BIT status and / or predetermined event status check S410 whereby each status check S410 determines the sampling frequency of one sensor or a group of sensors only. Therefore, for example, if a predetermined high pressure event was detected in S410, the increased sampling frequency would only be set for sensors relating to the predetermined high pressure event. In a next step S435 determined values for performance parameters monitored by sensors 340 at the increased sampling frequency are stored in the storage medium 380 with an event marker. The event marker indicates that said values were determined during / after a predetermined event occurred. Aptly the determined values for said performance parameters are stored for 1 hour. Aptly the determined values for said performance parameters are stored for two, three, four, six, eight, ten, twelve, or more hours. Aptly the determined values for said performance parameters are stored for one, two, three, four, six, eight, ten, twelve, or more days. Aptly the determined values for said performance parameters are stored until a command is issued to delete the determined values.

[0123] Although Figure 4 generally refers to varying the sampling rate for a single sensor 340 according to the BIT status and / or predetermined event status check step S410, it will be appreciated that alternatively the sampling rate of multiple sensors 340 may be varied according to the BIT status and / or predetermined event status check step S410. It will also be appreciated that alternatively there may be multiple check steps S410 running on the second processor 390 each corresponding to a different BIT and / or predetermined event thereby each varying the sampling rate of one or more sensors 340. Also, during the operation of the second processor 390, statistics about individual faults identified from any BIT and / or anomalies identified from the occurrence of any predetermined event may be recorded onto the storage medium 380. Said statistics may be transmitted to the MCS 132 and thereby or otherwise used for analytical purposes to determine how often a fault or anomaly occurs and / or how a fault or anomaly may be resolved.

[0124] Figure 5 illustrates a timeline 500 including numerous occasions at which a value is determined from the sensor 340i or 3402 or the like for one performance parameter associated with the subsea tree 320. The timeline 500 shown in Figure 5 may correspond to the function of the second processor 390 described with respect of Figure 4. The performance parameter may be 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 or the like. It will be appreciated that alternatively, said numerous occasions on the timeline 500 may correspond to when multiple values are determined from multiple sensors 340I,2 for multiple performance parameters associated with the subsea tree 320. The timeline 500 has a horizontal time axis 510 measured in seconds, minutes, hours, or the like whereby the direction of time in Figure 5 is from left to right. It will be appreciated that alternatively, the horizontal axis 510 could represent processor cycles or another regularly occurring event. In Figure 5, at a vertical line 520, a current value for the measurement parameter is determined by the sensor 340i. The current value is recorded to the storage medium 380. Vertical lines 520 are separated on the horizontal axis 510 by a time period 5. In other words, the time delay from one vertical line 520 to the following vertical line 520 is equal to the time period 5. It will be appreciated that the time period 5 is equal to the sampling frequency of the sensor 340 at that period in time.

[0125] During normal operation (ie before a predetermined event has occurred), the time period 5 is set to a predetermined first time period 61. Ai is equal to 1 second. That is to say the time delay between each repeated determining of a value for the performance parameter measured by the sensor 340i is 1 second. Aptly the first time period <5i is equal to a value greater than 1 second. Aptly the time period <5i is equal to a value of 0.5 seconds, 0.33 seconds, 0.25 seconds or any other value less than 1 second. Once a value for the performance parameter is determined, the value is stored in the storage medium 380. Aptly the value may be transmitted to the MCS 132.

[0126] After a predetermined event, ‘EVENT’, first occurs at an event trigger, verbose logging mode is initiated for the sensor 340i. The time period 5 is set to a predetermined second time period 62 for a predetermined length of time Pi. A2 is equal to 0.2 seconds. That is to say the time delay between each repeated determining of a value for the performance parameter measured by the sensor 340i is 0.2 seconds from the event trigger until Pi units of time after the event trigger. Aptly the second time period 62 is equal to a value greater than 0.2 seconds. Aptly the second time period 62 is equal to 0.17 seconds, 0.14 seconds, 0.13 seconds, or any other value less than 0.2 seconds. Once a value for the performance parameter is determined, the value is stored in the storage medium 380. Aptly the value may be transmitted to the MCS 132. Aptly the value may be recorded on the storage medium 380 with an event marker. The event marker indicates that said value was determined during / after a predetermined event occurred.

[0127] After the time period Pi following the event trigger, standard logging mode is initiated for the sensor 340i. In other words, after a predetermined threshold is reached, normal operation (ie as before a predetermined event has occurred) recommences. The time period Pi is equal to twenty minutes although it will be appreciated that alternatively the predetermined period of time may be thirty seconds, one minute, five minutes, ten minutes, thirty minutes, one hour or the like. In some embodiments the predetermined threshold is receipt of an instruction from the MCS 132. The instruction from the MCS 132 may correspond to an operator instruction or when a fault associated with the predetermined event is cleared. After Pi , the time period 5 is set to the predetermined first time period 5i of one second. Therefore the time delay between each repeated determining of a value for the performance parameter measured by the sensor 340i is one second. Aptly the first time period <5i is equal to a value greater than one second. Aptly the time period <5i is equal to a value of 0.5 seconds, 0.33 seconds, 0.25 seconds or any other value less than one second. Once a value for the performance parameter is determined, the value is stored in the storage medium 380. Aptly the value may be transmitted to the MCS 132. It will be appreciated that alternatively, the time period 5 may be set to a third time period 63.

[0128] Figure 6 illustrates a method 600 of automatically storing data in the SCM 350 according to a flowchart. The method 600 is executed by the second processor 390. It will be appreciated that the method 600 may alternatively be executed by the first processor 370 of the SEM 360. The method 600 relates in particular to the data flow diagram of Figure 4 and the timeline 500 of Figure 5. At a starting position S605, the first processor 370 reads a value for the performance parameter that the sensor 340 is measuring at a sampling rate that corresponds to the normal sampling frequency. The value for the performance parameter is recorded in the storage medium 380 in the same detail and at the same regularity as is determined by the normal sampling / polling frequency of the sensor 340. The normal sampling frequency at which the sensor 340 is polled is 1 Hz. Aptly the normal sampling frequency at which the sensor 340 is polled is less than 1 Hz. Aptly the normal sampling frequency of the sensor 340 is 2Hz, 3Hz, 4Hz or any other value greater than 1 Hz. Aptly the value for the performance parameter is stored for 1 hour. Aptly the value for the performance parameter is stored for two, three, four, six, eight, ten, twelve, or more hours. Aptly the value for the performance parameter is stored for one, two, three, four, six, eight, ten, twelve, or more days. Aptly the value for the performance parameter is stored until a command is issued to delete the value.

[0129] A next step S610 involves determining, at the second processor 390, that a predetermined event has occurred. The predetermined event could be the BIT error status of TRUE (1 in binary) or the satisfaction of a certain predetermined criterion including a measurement parameter of a performance parameter monitored by the sensor 340 exceeding a predetermined value. Aptly, the predetermined event may refer to a measurement parameter monitored by the sensor 340 falling below a predetermined value. Aptly, the predetermined event may refer to multiple measurement parameters monitored by multiple sensors 340 falling below or exceeding predetermined values in any combination concurrently. Aptly, the predetermined event may refer to certain data received by the subsea tree 320 or associated SEMS 360. The BIT is discussed further in the detailed description of Figure 4. It will be appreciated that there may be more than one BIT, where each BIT may determine that one or more predetermined events has occurred. The moment at which the predetermined event begins to occur is considered a predetermined event trigger. It will be appreciated that in some embodiments the BIT may return more data including details of any problems identified during the test.

[0130] If the step S610 of determining is FALSE, the step S610 is repeated after a predetermined period of time. The predetermined period of time is equal to one millisecond. Aptly the predetermined period of time is equal to one micro second, ten milliseconds, one second, one minute, one hour, or the like.

[0131] If the step S610 of determining is TRUE, at an event trigger, a next step S615 involves initiating, at the first processor 370, a verbose logging mode for polling the sensor 340 by issuing instructions to enable verbose mode from the second processor 390. The verbose logging mode corresponds to a key event recording period that begins with the event trigger.

[0132] A next step S620 involves increasing, at the first processor 370, the polling rate at which a value for the performance parameter measured by the sensor 340 is determined. The sampling rate at which the sensor 340 monitors the performance parameter and determined values of performance parameters are read by the first processor 370 is equal to the increased sampling frequency. The increased sampling / polling frequency of the sensor 340 is 5Hz. Aptly the increased sampling frequency of the sensor 340 is less than 5Hz. Aptly the increased sampling frequency of the sensor 340 is 6Hz, 7Hz, 8Hz or any other value greater than 5Hz. It will be appreciated that alternatively, one or more of a total number of sensors 340 may have a sampling rate equal to the increased sampling frequency. In other words it is possible for one or more sensors 340 to be polled for determined values for performance parameters at the increased sampling frequency whilst the remaining sensors 340 are polled for determined values for performance parameters at the normal sampling frequency.

[0133] A next step S625 involves storing, on the storage medium 380, each value determined by the sensor 340 for the performance parameter. The value for the performance parameter is recorded in the storage medium 380 in the same detail and at the same regularity as is determined by the increased sampling frequency of the sensor 340 in verbose logging mode. Aptly each value for the performance parameter is stored for one hour. Aptly each value for the performance parameter is stored for two, three, four, six, eight, ten, twelve, or more hours. Aptly each value for the performance parameter is stored for one, two, three, four, six, eight, ten, twelve, or more days. Aptly each value for the performance parameter is stored until a command is issued to delete the value. During the key event recording period, the values are stored with an event marker which signifies that the values correspond to the key event recording period. Aptly, statistics about individual faults identified from any BIT and / or anomalies identified from the occurrence of any predetermined event may be recorded onto the storage medium 380. Said statistics may be transmitted to the MCS 132 and thereby or otherwise used for analytical purposes to determine how often a fault or anomaly occurs and / or how a fault or anomaly may be resolved.

[0134] A next step S630 involves detecting a predetermined threshold is satisfied and initiating a standard logging mode. In standard logging mode the sampling rate of the sensor 340 is equal to the normal sampling frequency. In standard logging mode the values determined by the sensor 340 are not verbose. The predetermined threshold is satisfied by the end of the time period Pi, where the time period Pi begins from the event trigger. In other words, the verbose logging mode of steps S615 to S625 is enabled from when the predetermined event is detected to the period of time Pi after the predetermined event trigger. Aptly the predetermined threshold is satisfied when the fault of the predetermined event is cleared. Aptly the predetermined threshold is satisfied when an instruction to end verbose logging mode is issued by an operator of the MCS 132. After the next step S630 when verbose logging is ended, in a next stage 635, the step S610 is repeated after a predetermined period of time. The predetermined period of time is equal to one millisecond. Aptly the predetermined period of time is equal to one microsecond, ten milliseconds, one second, one minute, one hour, or the like.

[0135] Although Figure 6 generally refers to varying the sampling / polling rate for a single sensor 340 according to the BIT status and / or predetermined event status check step S410, it will be appreciated that alternatively the rate of multiple sensors 340 may be varied according to the BIT status and / or predetermined event status check step S410. It will also be appreciated that alternatively there may be multiple check steps S410 running on the second processor 390 each corresponding to a different BIT and / or predetermined event thereby each varying the sampling rate of one or more sensors 340.

[0136] Figure 7 illustrates a function of the second processor 390 using a data flow diagram, according to an alternative embodiment. It will be appreciated that the data flow diagram illustrated in Figure 7 is similar to the data flow diagram illustrated in Figure 4, including the first processor 370, storage medium 380 and second processor 390. The data flow diagram in Figure 7 also includes a second non-volatile storage medium 710. The second storage medium 710 is used to temporarily store data. The second storage medium 710 is located in the SEM 360 but is physically distinct from the storage medium 380. Alternatively, in some embodiments the second storage medium 710 may be the storage medium 380. Alternatively, in some embodiments the second storage medium 710 may be located outside the SEM 360. The data link between the first processor 370 and the second processor 390 is facilitated by an ethernet connection. Aptly, the data link between the first processor 370 and the second processor 390 is alternatively facilitated by a fibre connection, cable connection, wireless connection or the like. Periodically, at predetermined time intervals, the first processor 370 runs a Built In Test (BIT). The BIT evaluates the normal functioning of the SEM 360, subsea tree 320 and associated components such as valves 330, sensors 340, network connections and the like. The BIT thereby checks that the subsea tree 320 is functioning correctly. The BIT returns a BIT error status of either TRUE or FALSE. Aptly the BIT status is alternatively either FAIL, corresponding to a 0 in binary, or PASS, corresponding to a 1 in binary. It will be appreciated that in some embodiments the BIT may return more data including details of any problems identified during the test. It will be appreciated that there may be more than one BIT running periodically.

[0137] Unlike in Figure 4, at a first step S720, a verbose logging mode is already initiated for the sensor 340. In other words, the sampling rate at which the sensor 340 monitors the performance parameter and determined values of the performance parameter are read by the first processor 370 is equal to the increased sampling frequency. It will be appreciated that the increased sampling frequency may be referred to as a first sampling rate. The increased sampling / polling frequency of the sensor 340 is 5Hz. Aptly the increased sampling frequency of the sensor 340 is less than 5Hz. Aptly the increased sampling frequency of the sensor 340 is 6Hz, 7Hz, 8Hz or any other value greater than 5Hz. It will be appreciated that alternatively, one or more of a total number of sensors 340 may have a sampling rate equal to the increased sampling frequency. In other words it is possible for one or more sensors 340 to determine values for performance parameters at the increased sampling frequency whilst the remaining sensors 340 determine values for performance parameters at the normal sampling frequency discussed with respect to Figure 4.

[0138] Periodically, at predetermined time intervals, the second processor 390 checks the BIT status and / or a predetermined event status at a next step S730. The predetermined event status may refer to the occurrence of a predetermined event at the present time, whereby if the predetermined event is occurring then the predetermined event status is set to TRUE If the predetermined event is not occurring then the predetermined event status is set to FALSE. In some embodiments, if the predetermined event occurs then the predetermined event status is set TRUE and will remain TRUE until the predetermined event status is reset (ie manually set to FALSE). It will be appreciated that there may be multiple predetermined event statuses to be checked. The predetermined event may refer to a measurement parameter of a performance parameter monitored by the sensor 340 exceeding a predetermined value. Aptly, the predetermined event may refer to a measurement parameter monitored by the sensor 340 falling below a predetermined value. Aptly, the predetermined event may refer to multiple measurement parameters monitored by sensors 340 falling below or exceeding predetermined values in any combination concurrently. Aptly, the predetermined event may refer to certain data received by the subsea tree 320 or associated SEMS 360. In either outcome of the step S730, in a next step S740 the values for the performance parameters determined by the sensors 340 are stored in the second storage medium 710 at the increased sampling frequency. That is to say the values for the performance parameters determined by the sensors 340 are recorded in verbose mode in the second storage medium 710 for a predetermined period of time. After a value has been stored in the second storage medium 710 for the predetermined period of time it is then deleted.

[0139] If the BIT error status and / or predetermined event status from the earlier step S730 is FALSE then a next step S750 follows the previous step S740. A predetermined number of sequential values (n) for the performance parameter determined by the sensor 340 are averaged to produce an averaged value for the performance parameter, thereby reducing the increased sampling rate (i) of the sensor 340 to a lower effective sampling rate (e) of the sensor 340 according to a formula 1 : e = i / n 1

[0140] The average used in the next step S750 is a median. Aptly, the average used in the next step S750 is a mode. Aptly, the average used in the next step S750 is a mean. Aptly more advanced statistics such as outlier identification or the like could be used to produce the averaged value. In Figure 7, the predetermined number of sequential values (n) is 5, the increased sampling rate is 5Hz and the effective sampling rate is 1 Hz. It will be appreciated that alternatively a higher or lower number of sequential values could be used thereby increasing or reducing the effective sampling / polling rate of the sensor 340. It will be appreciated that the effective sampling rate may be a normal sampling rate. The normal sampling rate may be associated with a rate of determining performance parameter values associated with uneventful record values. The average value for the performance parameter determined by the sensor 340 is recorded in the storage medium 380. Aptly the average value for said performance parameter is stored for one hour. Aptly the average value for said performance parameter is stored for two, three, four, six, eight, ten, twelve, or more hours. Aptly the average value for said performance parameter is stored for one, two, three, four, six, eight, ten, twelve, or more days. Aptly the average value for said performance parameter is stored until a command is issued to delete the average value.

[0141] If the BIT error status and / or predetermined event status from the earlier step S730 is TRUE (1 in binary) then a next step S760 follows the previous step S740 and an event trigger occurs. All of the values for the performance parameter monitored by the sensor 340 stored in the second storage medium 710 before and after the event trigger are stored in the storage medium 380. In other words, the values for the performance parameter monitored by the sensor 340 at the increased sampling / polling frequency immediately prior and following the event trigger are recorded verbosely in the storage medium 380. Aptly the determined value for said performance parameter is stored for one hour. Aptly the determined value for said performance parameter is stored for two, three, four, six, eight, ten, twelve, or more hours. Aptly the determined value for said performance parameter is stored for one, two, three, four, six, eight, ten, twelve, or more days. Aptly the determined value for said performance parameter is stored until a command is issued to delete the determined value. Therefore in the next step S760, verbose data on the performance parameter relevant to the BIT error and / or predetermined event which has occurred is stored and can be reviewed when required.

[0142] Although Figure 7 generally refers to varying the sampling rate for a sensor 340 according to the BIT status and / or predetermined event status check step S730, it will be appreciated that alternatively the sampling rate of multiple sensors 340 may be varied according to the BIT status and / or predetermined event status check step S730. It will also be appreciated that alternatively there may be multiple check steps S730 running on the second processor 390 each corresponding to a different BIT and / or predetermined event thereby each varying the sampling rate of one or more sensors 340. Also, during the operation of the second processor 390, statistics about individual faults identified from any BIT and / or anomalies identified from the occurrence of any predetermined event may be recorded onto the storage medium 380. Said statistics may be transmitted to the MCS 132 and thereby or otherwise used for analytical purposes to determine how often a fault or anomaly occurs and / or how a fault or anomaly may be resolved. Figure 8 illustrates the timeline 500 according to an alternative embodiment including numerous occasions at which a value is determined from the sensor 340i or 3402 or the like for one performance parameter associated with the subsea tree 320. The timeline 500 shown in Figure 8 may correspond to the function of the second processor 390 described with respect of Figure 7. The performance parameter may be 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 or the like. It will be appreciated that alternatively, said numerous occasions on the timeline 500 may correspond to when multiple values are determined from multiple sensors 340I,2 for multiple performance parameters associated with the subsea tree 320. The timeline 500 includes the horizontal time axis 510 measured in seconds, minutes, hours, or the like whereby the direction of time in Figure 8 is from left to right. It will be appreciated that alternatively, the horizontal axis 510 could represent processor cycles or another regularly occurring event. In Figure 8, at any vertical line 520, a current value for the measurement parameter is determined by the sensor 340i. The current value is recorded to the storage medium 380. Vertical lines 520 are separated on the horizontal axis 510 by a time period 5. In other words, the time delay from one vertical line 520 to the following vertical line 520 is equal to the time period 5. It will be appreciated that the time period 5 is equal to the sampling frequency of the sensor 340 at that period in time.

[0143] During normal operation (ie before a predetermined event has occurred), the time period 5 is set to a predetermined third time period 63. 63 is equal to 0.2 seconds. That is to say the time delay between each repeated determining of a value for the performance parameter measured by the sensor 340i is 0.2 seconds. Aptly the third time period 62 is equal to a value greater than 0.2 seconds. Aptly the third time period 63 is equal to a value of 0.17 seconds, 0.14 seconds, 0.13 seconds or any other value less than 0.2 seconds. Aptly the third time period 63 is equal to the second time period 62. Once numerous sequential values for the performance parameter are determined, the values are averaged according to step S650 and the average value is stored in the storage medium 380. Aptly the average value may be transmitted to the MCS 132.

[0144] If a predetermined event, ‘EVENT’ occurs, at an event trigger, values for the performance parameter measured by the sensor 340i preceding the event trigger within a predetermined time period P2 are recorded in the storage medium 380. Additionally values for the performance parameter measured by the sensor 340i following the event trigger within a predetermined time period P3 are also recorded in the storage medium 380. Aptly the values measured within the time periods P2 and / or P3 may be transmitted to the MCS 132. Aptly the values measured within the time periods P2 and / or P3 may be recorded on the storage medium 380 with an event marker. The event marker indicates that said values were determined during / after a predetermined event occurred. The recording of values for the performance parameter preceding the event trigger within the time period P2 is facilitated by temporarily storing all values in verbose mode in the second storage medium 710 to be transferred to the storage medium 380 if required, as described in step S750. The time period P3 is equal to ten minutes. Aptly the time period P3 is equal to fifteen seconds, one minute, two minutes, five minutes, thirty minutes, one hour or the like. Aptly the time period P3 is equal to the time period P2. Aptly the time period P3 is not equal to the time period P2. Alternatively the time period P3 may instead be defined by a predetermined threshold. In some embodiments the predetermined threshold is receipt of an instruction from the MCS 132. The instruction from the MCS 132 may correspond to an operator instruction or when a fault associated with the predetermined event is cleared.

[0145] Figure 9 illustrates a method 900 of storing data in the SCM 350 according to an alternative embodiment. The method 900 is executed by the second processor 390. It will be appreciated that the method 900 may alternatively be executed by the first processor 370 of the SEM 360. The method 900 relates in particular to the data flow diagram of Figure 7 and the timeline 500 of Figure 8. At a starting position S905, the first processor 370 reads a value for the performance parameter that the sensor 340 is measuring at a sampling / polling rate that corresponds to the increased sampling frequency. The increased frequency at which the sensor 340 is polled is 5Hz. Aptly the increased frequency at which the sensor 340 is polled is less than 5Hz. Aptly the increased sampling frequency of the sensor 340 is 6Hz, 7Hz, 8Hz or any other value greater than 5Hz.

[0146] A next step S910 involves storing temporarily, on the second storage medium 710, each value determined by the sensor 340 for the performance parameter. The value for the performance parameter is recorded in the second storage medium 710 in the same detail and at the same regularity as is determined by the increased sampling / polling frequency of the sensor 340 in verbose logging mode. A given value is stored for the predetermined period of time P2 after the given value is first determined by the sensor 340 before the given value is then deleted. The time period P2 is equal to ten minutes. Aptly the time period P2 is equal to fifteen seconds, one minute, two minutes, five minutes, thirty minutes, one hour or the like. A next step S915 involves determining, at the second processor 390, that a predetermined event has occurred. The predetermined event could be the BIT error status of TRUE or the satisfaction of a certain predetermined criterion including a measurement parameter of a performance parameter monitored by the sensor 340 exceeding a predetermined value. Aptly, the predetermined event may refer to a measurement parameter monitored by the sensor 340 falling below a predetermined value. Aptly, the predetermined event may refer to multiple measurement parameters monitored by multiple sensors 340 falling below or exceeding predetermined values in any combination concurrently. Aptly, the predetermined event may refer to certain data received by the subsea tree 320 or associated SEMS 360. The BIT is discussed further in the detailed description of Figure 7. It will be appreciated that there may be more than one BIT, where each BIT may determine that one or more predetermined events has occurred. The moment at which the predetermined event begins to occur is considered a predetermined event trigger. It will be appreciated that in some embodiments the BIT may return more data including details of any problems identified during the test.

[0147] If the step S915 of determining is FALSE, a next step S920 involves averaging a plurality of determined values of the performance parameter. A predetermined number of sequential values (n) for the performance parameter determined by the sensor 340 are averaged to produce an averaged value for the performance parameter, thereby reducing the increased sampling rate (i) of the sensor 340 to a lower effective sampling rate (e) of the sensor 340 according to the formula 1 : e = i / n 1

[0148] The average used in the step S920 is a median. Aptly, the average used in the step S920 is a mode. Aptly, the average used in the step S915 is a mean. Aptly more advanced statistics such as outlier identification or the like could be used to produce the averaged value. The predetermined number of sequential values (n) is 5. The increased sampling rate is 5Hz. The effective sampling rate is 1 Hz. It will be appreciated that alternatively a higher or lower number of sequential values could be used thereby increasing or reducing the effective sampling / polling rate of the sensor 340.

[0149] A next step S925 involves storing respective averaged values as uneventful record values during periods of time outside a key recording period. The average value for the performance parameter determined by the sensor 340 is recorded in the storage medium 380. Aptly the average value for said performance parameter is stored for one hour. Aptly the average value for said performance parameter is stored for two, three, four, six, eight, ten, twelve, or more hours. Aptly the average value for said performance parameter is stored for one, two, three, four, six, eight, ten, twelve, or more days. Aptly the average value for said performance parameter is stored until a command is issued to delete the average value. After the step S925, in a stage 926, the step S910 is repeated after a predetermined period of time. The predetermined period of time is equal to one millisecond. Aptly the predetermined period of time is equal to one microsecond, 10 milliseconds, one second, one minute, one hour, or the like.

[0150] If the step S915 of determining is TRUE, after an event trigger, a next step S930 involves continuing to determine and store temporarily, on the second storage medium 710, each value determined by the sensor 340 for the performance parameter. The value for the performance parameter is recorded in the second storage medium 710 in the verbose logging mode and at the same regularity as the sampling rate that corresponds to the increased sampling frequency for the predetermined period of time P3 after the event trigger.

[0151] A next step S935 involves storing, on the storage medium 380, the values stored temporarily on the second storage medium 710. In other words, the values for the performance parameter measured by the sensor 340i preceding the event trigger within the predetermined time period P2 are recorded in the storage medium 380. Additionally values for the performance parameter measured by the sensor 340i following the event trigger within the predetermined time period P3 are also recorded in the storage medium 380. Aptly the values measured within the time periods P2 and / or P3 may be transmitted to the MCS 132. Aptly the values measured within the time periods P2 and / or P3 may be recorded on the storage medium 380 with an event marker. The event marker indicates that said values were determined during / after a predetermined event occurred. After the step S935, in a next stage 936, the step S910 is repeated after a predetermined period of time. The predetermined period of time is equal to one millisecond. Aptly the predetermined period of time is equal to one microsecond, ten milliseconds, one second, one minute, one hour, or the like.

[0152] Although Figure 9 generally refers to varying the sampling rate that is recorded (the actual sampling / polling rate) for a single sensor 340 according to the occurrence of a predetermined event, it will be appreciated that alternatively the actual rate at which multiple sensors 340 are sampled may be varied according to the occurrence of a predetermined event. It will also be appreciated that alternatively there may be multiple determining steps S915 running on the second processor 390 each corresponding to a different occurrence of a predetermined event thereby each varying the polling rate of one or more sensors 340. It will also be appreciated that a second predetermined event may occur during the predetermined time period P3 after a first predetermined event trigger. The second predetermined event will also be recorded as outlined in step S935.

[0153] Figure 10 illustrates an alternative embodiment of Figure 3 whereby the second processor 390 is located on a Remotely Operated Vehicle (ROV) 1010. Figure 10 illustrates the wellhead 310 and subsea tree 320 shown in Figure 3. The subsea tree 320 includes the valves 330, sensors 340 SCM 350 and SEMs 350 shown in Figure 3. The sensors 340 may be connected to the SCM 350 by a wired connection or a wireless connection. The SEMs 360I,2 shown in Figure 10 include the first processor 370 and the non-volatile storage medium 380. The second processor 390 previously shown in Figure 3 as being located in the SEMs 360I,2 is now located in the ROV 1010.

[0154] The ROV 1010 is connected via a cable 1020 to the MOS 132. The cable 1020 is an umbilical 1020. The umbilical 1020 contains a fibre optic connection for transferring information, although it will be appreciated that the umbilical 1020 could alternatively contain a fast copper connection, other wired connection, wireless connection or the like. The ROV 1010 includes a processor 1030, a non-volatile storage medium 1040 and the second processor 390. The processor 1030 executes one or more instructions from the storage medium 1040. The ROV 1010 is connected to the subsea tree 320 via a wet mate connector 1050. Therefore data may be transferred between the ROV 1010 and the SCM 350. It will be appreciated that alternatively the ROV 1010 may be connected to the subsea tree 320 to transfer data using any wired connection such as ethernet, optical fibre, copper cable or the like, or any wireless connection such as radio telemetry, Bluetooth, sonar, light, or the like.

[0155] 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.

[0156] 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. 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 storing data at a subsea module, comprising the steps of: determining that at least one predetermined event has occurred and a respective time of occurrence; at a first sampling rate and at least subsequent to said time of occurrence, repeatedly determining a value for each of at least one performance parameter associated with a subsea module at a subsea location; for each occurrence, storing key record values indicative of determined values for said performance parameters determined at the first sampling rate for a period of time, comprising a key event recording period; and determining said a value at the first sampling rate repeatedly at a greater frequency than an effective sampling rate of determining performance parameter values associated with uneventful record values that are stored and that are indicative of determined values outside of a key event recording period.

2. The method as claimed in any preceding claim, further comprising: determining said a value at the first sampling rate at all times and storing respective key record values for each determined value associated with a period of time before and after the time of occurrence.

3. The method as claimed in claim 2, further comprising: repeatedly averaging a plurality of determined values and storing respective averaged values as uneventful record values during periods of time outside of a key event recording period.

4. The method as claimed in claim 1 , further comprising: determining each said a value at a normal sampling frequency less than the first sampling rate and corresponding to the effective sampling rate until a predetermined event is determined to have occurred and then determining each said a value at the first sampling rate until a predetermined threshold is satisfied.

5. The method as claimed in claim 4, further comprising: the predetermined threshold is elapse of a predetermined time period or receipt of confirmation that an event has ceased or receipt of an indication that an operatorhas indicated that the first sampling rate determination is to cease and sampling at the normal sampling frequency is to resume.

6. The method as claimed in claim 1 , comprising: determining that a predetermined event has occurred subsequent to a preceding uneventful period set apart in time by a predetermined period of time from said time of occurrence.

7. The method as claimed in any preceding claim, further comprising: determining that the predetermined event has occurred at at least one subsea module that optionally comprises at least one SEM or at least one SCM.

8. The method as claimed in any preceding claim, further comprising: repeatedly determining determined values immediately after said time of occurrence or immediately after a delay time has expired subsequent to said time of occurrence.

9. A method of providing performance related data to a topside node of a communication network, comprising the steps of: at a subsea module disposed at a subsea location, storing key record values associated with occurrence of a key event and storing uneventful record values for each period of time not associated with occurrence of a key event; and providing key event record values and uneventful record values as performance related data from the subsea module to a topside node of a communication network thereby providing key record values associated with a more frequent sampling rate than the uneventful record values.

10. The method as claimed in claim 9, further comprising: at the subsea module, determining a value for each of at least one performance parameter associated with the subsea module and storing key record values indicative of determined values determined at a first sampling rate for a period of time comprising a key event recording period.

11. The method as claimed in claim 9 or claim 10, further comprising: at the subsea module, determining a value for each of at least one performance parameter at a first sampling rate repeatedly at a greater frequency than an effective sampling rate of determining performance parameter values associated with uneventful record values that are stored at the subsea module and that are indicative of determined values outside of a key event recording period.

12. The method as claimed in any one of claims 9 to 11 , further comprising: providing performance related data to the topside node for each period of time, comprising a key event recording period, associated with each occurrence of a respective predetermined event.

13. The method as claimed in any one of claims 9 to 12, further comprising: providing an operator at a user interface (III) at a topside location associated with the topside node with the performance related data; and via the operator III, selecting an action and providing an instruction signal to the subsea module responsive thereto.

14. The method as claimed in any one of claims 9 to 13, further comprising: providing the key record values as detailed data that is more detailed per unit time than the uneventful record values.

15. The method as claimed in any one of claims 9 to 14, further comprising: transferring key record values from the subsea module to the topside node as transfer data having a greater information content than transfer data provided by uneventful record values transferred from the subsea module to the topside node.

16. A subsea module locatable at a subsea location, comprising: a first processor element for receiving sensor data from at least one sensor and / or executing a test procedure at a subsea module; a further processor element responsive to a determination that at least one predetermined event has occurred, for storing the key record values in a first data store and uneventful record values in a further data store, said key record values indicative of determined values for at least one performance parameter determined at a first sampling rate that has a more frequent frequency than an effective sampling rate ofdetermining performance parameter values associated with the uneventful record values.

17. The subsea module as claimed in claim 16, further comprising: the first data store and the further data store are distinct and separate data stores or are respective partitioned areas of a common data store.

18. The subsea module as claimed in claim 16 or claim 17, further comprising: the further processor element comprises an event detector that detects if a predetermined event has occurred and a respective time of occurrence for each event.

19. The subsea module as claimed in any one of claims 16 to 18, further comprising: the further processor element is spaced apart from a primary processor element of an SEM or SCM.

20. The subsea module as claimed in any one of claims 16 to 19, further comprising: the further processor element includes an initiation signal generator that generates an initiation signal to provide greater information content from the first processor element and is disposed to selectively provide the initiation signal to the further processor element.

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