SCADA-06-141

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Introduction As subsea processing and instrumentation is being added, traditional subsea controlsystems cannot accommodate the additional data throughput required. Subsea controlsystems will need to be able to deliver large amounts of data, and will need simpliedconnectivity so an increasing amount of sensors and production-boosting equipmentcan be added to the system.

e ability to use these large amounts of data in verifying the condition of the subsea production system is important. Systems will be provided that give assistance, eitheradvisory or automatic, to the operator. is assistance will help monitor the health of the subsea system or assist in optimising the overall subsea system performance.

is paper will present next generation subsea systems starting with the current status of subsea processing and boosting systems, including the level of benets that an operatorcan expect from these types of systems. e paper will also cover for electrical eld—ore-eld—solutions, both the use of data for condition monitoring and the optimisationof production. Specically, the paper will show how subsea data can be used to predictfailure or maintenance cycles.

e nal part of the paper will identify the changes that have occurred to the controlsystem that makes the delivery of good, timely data achievable. e use of bre opticsand open systems means that third-party devices are able to connect easily to the subsea production system and to deliver consistently the required amount of data so that deci-sions can be made.

e conclusion of this paper will propose a system built with subsea processing to im-prove recovery. Where the subsea system is closely monitored to ensure it is working

Subsea Architectures To Facilitate Increased Recovery from Reservoirs: Subsea Processing,

Condition Monitoring and Process Optimisationin a Modern Subsea Control SystemR Neri and K Falk Aker Kværner, Norway

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optimally. Large amounts of data are interpreted to optimise both the production fromthe well and the uptime of the system.

e infrastructure required to bring about this monitoring and control will allow the

easy connectivity to the subsea control system of devices, which will have the bandwidththey require to correctly monitor the well and subsea control system.

All of these areas together will facilitate an increased recovery from the subsea well.

Subsea Processing and Boosting Depending on the different needs for subsea processing, Aker Kværner Subsea has de-veloped different solutions that may be applied during the whole production lifetime orinserted at eld late life to increase oil recovery and to handle large amounts of produced

water. Relevant process solutions are listed below:

• MultiBooster™ system—subsea multiphase pumping e MultiBooster™ system consists of one or multiple MultiBooster units integrated

into a subsea process system. e multiphase pumps can either be arranged in parallelfor increasing capacity of well uid boosting, or serial for increasing differentialboosting pressure for well uid across the pumping process system.

• DeepBooster™ system—subsea separation and boosting e DeepBooster™ system is a subsea processing system for separation of the well

uid into a gas phase and a liquid phase followed by pressure boosting of the liquid

phase. Each of the phases is transported separately to topside dedicated risers. esystem will accommodate the lifetime changes in hydrocarbon and water productionand is especially well suited in applications from mid-deep to ultra-deep water.

• FlexSep™ system—subsea water separation and re-injectione FlexSep™ system is a subsea process system for separation of water from the well

uid and re-injection of the separated water into a subterranean formation. It con-sists of a hydrocarbon-water retrievable gravity separator module with solid removalarrangement and a retrievable liquid pump module.

• SeaBooster™ system—subsea raw seawater injectione SeaBooster™ system is the Aker Kværner Subsea Raw Seawater Injection System.e SeaBooster™ system operates by ltering the surrounding seawater before pumping

it, via an injection well, into a subterranean reservoir for maintaining reservoir pres-sure as oil is extracted from the reservoir.

Aker Kværner Subsea has successfully installed a MultiBooster™ pump at the Lyell Field(CNR) at 150 m in the North Sea. In addition Aker Kværner Subsea has been awardedthe contract for installing two MultiBooster™ subsea pumps at 1800-m water depth atthe King Field, Gulf of Mexico (BP). e pumps will be installed during 2007.

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All components in the MultiBooster system are qualied for subsea use. All of this work, combined with other initiatives, builds up into the Aker Kværner e-eld strategy.During the autumn of 2005 a major survey of our customers allowed us to build ane-eld strategy that is described in the following section.

E-Field Modele Aker Kværner e-eld products are developed in four consecutive steps: surveillance,

analysis, optimisation and advanced control, and remote operations. ese four steps aredirectly linked to the e-eld stage model commonly used by operators in the industry.

1. Surveillance—instrumentation

• Obtain real-time data to improve day-to-day asset management

• Install the right data infrastructure and instrumentation to collect sufficient data inreal time or near real time

2. Analysis—information in real-time

• Validate and visualise data

• Analyse data in (near) real time to move from data to information

3. Optimisation and advanced control—intervention in real-time

• Closed loop or man-in-the-loop implementation of optimal operational actionsbased on data or processed data

4. Remote operations—innovative business solutions

• Transform the way we operate

• Use of innovative technologies, new processes and virtual teams

e logic behind the above classication is that in the rst stage, measurements areviewed directly.

In the second stage the measurements are used intellectually (e.g. in a model) to pro-vide new pieces of information. is stage includes for instance soft-sensoring, whichspans from estimating the performance of a single piece of equipment to online eld-

wide multiphase ow simulations. e widely used terms condition/performance/assetmonitoring typically fall into the rst and second category. Solutions that give adviceon set-point values, or that give set-point values in a closed loop, fall into the thirdcategory.

Typical for e-eld solutions is that the information and the access to systems need to bemade available remotely since there is a strong drive towards less manning and expertiseat the actual plant. Solutions that enable this fall into the fourth category.

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Figure 1: MultiBooster System

Figure 2: E-Field Solutions Applications

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Solutions in all categories require interaction with the control system, and Aker KværnerSubsea has strong subsea control system solutions that allow interaction with a variety of e-eld solutions.

Cost-Saving Potential e main driver behind most e-eld solutions is to increase production to make the eldmore protable. With an increased production rate the eld stays protable for a longertime and hence the recovery factor can be increased. E-eld solutions may increaseproduction directly, for instance by optimising well rates, or indirectly, for instance by monitoring equipment to prevent downtime.

Health, Safety and Environment (HSE) Improvements In terms of environmental impact, several e-eld solutions are contributing to a moreenvironmentally friendly development of oil and gas elds. Typical examples are hydrateestimation, which enables less use of chemicals, and leakage detection, which preventsleakages of environmentally unfriendly gases and liquids to the sea.

Example with Condition Monitoring for Subsea Boosting As pumps and other rotating equipment are being installed subsea, new challenges oc-cur that are related to diagnostics, residual life prediction and early fault detection.

Figure 3:Operation Condition Monitoring at Aker Kværner Offices via DM2000

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Traditionally, operators have inspected topside rotating equipment by looking, feeling and, in other ways, observing the pumps and other equipment. Subsea, there is a needfor alternative means for observing the equipment, for example through vibration meas-urements. ere are huge costs, especially related to downtime, if a booster breaks downat an inconvenient point in time. For instance, rough waters during winter time may make maintenance impossible, whereas a booster can be replaced at a relatively low costif done as part of a planned shut-down.

Aker Kværner Subsea has already installed vibration sensors on a subsea booster, andhas keyed the competence for analysing the measurements. is expertise comes via the use of the DM2000 system at the facility in Tranby. is system allows an expert toaccess remotely data from a number of surface pumps in the Norwegian sector of theNorth Sea. is is an excellent example of the use of expertise onshore to solve problemsoffshore.

Aker Kværner is currently involved in research and development (R&D) activities withStatoil, ABB, SKF and IBM through the ASTI project ‘Concepts for Safe and Cost-Efficient Operations of Facilities’. One of the focus areas in this project is conditionand performance monitoring, and Aker Kværner is specically targeting monitoring of subsea pumps, in addition to conventional subsea equipment. e goal is to do early fault detection, diagnostics and residual life estimation. Within the ASTI project, thequestion of whether there is enough information in the signals to enable residual life-time estimates will be investigated.

Subsea Control System Architecturee architecture of the subsea control system needs to change to be able to accommo-

date the update rate and levels of data that will be required from a subsea control systemif the full benets of subsea processing and e-eld are to be realised.

Current Subsea Control Systems e current subsea control system architectures do not allow for a large amount of data

to be transferred on a routine basis.

e majority of the subsea communications bandwidth is used for operation and moni-toring of traditional subsea equipment such, as tree valves and tree sensors. ird-party sensors, such as sand detectors or downhole gauges, are also monitored by the subsea control system. e data must be coded into the proprietary control system language tobe sent to the surface. e data rate to these devices is typically at a baud rate of 9600and must be shared along with the process data.

Facilitating Increased Recovery from Reservoirs Requirements In order to facilitate increased recovery from reservoir the subsea control system archi-tecture needs to full new requirements.

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e subsea control systemneeds to be able to interfaceto new devices subsea. esemay range from for example‘intelligent well’ comple-tion, leak detection sensors,seismic data or distributedtemperature systems. Anability to add these devices asquickly and cheaply as possi-ble will be needed. is willallow decisions on the bestdevices to be made as late aspossible in a project.

e simplicity of connec-tion and interface of thesedevices is also crucial, allow-ing a ‘plug and play’ connec-tion to the subsea controlsystem. e use of intelligent

well interface standardisation(IWIS) will greatly simplify

the connection of devicesand for any other systemsthat are to be connected. e removal of any decoding of messages within the subsea control system will lead to the easy connection of devices any time during the project.Reliability is also improved as the interfaces across vendors become standardised.

A move towards fastercommunications speed

with the use of bre op-tic systems is required

to allow larger amountsof data to be returnedin a timely manner.Successful installationand operation of -bre optic controls onthe Canyon Expressproject have increasedcondence in suchtechnology.

Figure 5: IWIS Implementation

Figure 4: Current Control System Architecture

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Devices such as leak detection sensors based on sonar technology (e.g. Aquadyne) willrequire le transfer across the umbilical with sizes reaching 5 MB per image. e subsea control system will improve HSE and increased uptime by providing better and morereliable condition monitoring.

Increased recovery from the reservoir may also be achieved through automated processoptimisation. In order to achieve this, the placement and accuracy of subsea sensors arecrucial as both will directly affect the performance of the optimisation tools. Well placedsensors may result in very good outcomes, whereas poorly placed sensors may disablethe possibility of estimating certain quantities with the required accuracy.

Condition monitoring and validation of the sensors is benecial in achieving reliableresults. It is a great benet if drifting sensors can be identied, and if possible, an esti-mate for the correct value can be provided. Estimation of physical properties in areas

where there is no physical sensor is often referred to as soft sensoring, and this kind of technique is typically what will be used for sensor validation.

Solution Subsea Control Systems Architecture Subsea control system architecture may encapsulate all the above requirements in orderto achieve increased recovery from the reservoir. Standard interfaces to subsea device,

Figure 6:SolutionSubsea ControlSystems

Architecture

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faster communications through the use of bre optic, automated optimisation of theprocess and condition monitoring of the subsea installation and sensors will be part of such an architecture.

Conclusion A subsea control system that will help to increase recovery from subsea wells will needmany more features than the current traditional system. e use of subsea processing and boosting will provide an ability to either extend the normal life of a eld or increasethe production in the early stages. e placing of more complex machinery subsea willrequire condition monitoring to ensure that the systems are working correctly.

e retrieval of evermore data from the subsea well will allow both more complex con-dition monitoring of other parts of the system, as well as the possibility to optimise

production to retrieve the maximum recovery from the well. is optimisation couldbe in the form of manual assistance to an operator or automatic where the optimisationsystem will make quick decision on the best way to produce.

e transfer of data from the subsea eld to experts back onshore will facilitate the fastresolution of problems as and when they occur. e control system that will be neededto make the above requirements possible must to allow for the easy connection of subsea devices, the ability to mix different protocols on the umbilical, the use of subsea processcontrol and the ability to transfer large amounts of data to the surface.

A subsea production system that has all of these elements will allow the recovery fromthe subsea wells to begin to approach the recovery from surface wells.

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SCADA-06-141