L08 - SUBSEA CONTROL SYSTEMS

L8 - SUBSEA CONTROL SYSTEMS & UMBILICALS •

SYSTEMS

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TYPES

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ELECTRO-HYDRAULIC MULTIPLEXED SYSTEMS

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TOPSIDES & SUBSEA COMPONENTS

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OPERATIONS

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UMBILICALS

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CHEMICAL INJECTION

PRINCIPAL COMPONENTS OF SUBSEA PRODUCTION CONTROL SYSTEM ARRANGEMENT FOR TIE_BACK TO HOST PLATFORM

CONTROL SYSTEMS FUNCTIONS The control of the components of a production system is managed by the subsea production control system. Control functions include : y Opening and closing subsea tree production, annulus and crossover valves. y Opening and closing the SCSSV. y Opening and closing subsea production manifold flowline valves and pigging valves. y Opening and closing chemical injection valves. y Adjusting subsea choke position. y Monitoring pressure, temperature and other data from treemounted, manifold mounted or downhole instrumentation.

CONTROL SYSTEM / DESIGN ISSUES Key design issues that must be considered when specifying or designing the subsea control system: y Offset distance. Distance affects signal strength, hydraulic pressure loss, response time and cost. y Valve control requirements: The number of valves, types of valves, types of actuators, size of valves, failure position of valves. y Chemical injection requirements. Valve operation, umbilical sharing. y Instrumentation requirements: Pressure or temperature monitoring, pig detection. y Installation and workover requirements and interface with the IWOC system. y Redundancy requirements / availability y Expandability. Future wells, future flowline tie-ins

CONTROL SYSTEMS TYPES Types of Control Systems There are four basic types of production control systems: y Direct Hydraulic Control System y Piloted Hydraulic Control System (Discrete and Sequential) y Electro-Hydraulic Piloted Control System y Electro-Hydraulic Multiplexed Control System Only 1 and 4 considered further here

Characteristics of Different Types of Control Systems Response Rate Features Systems Direct

Umbilical(s) Discrete Control

Complexity

Signal

Actuation

Subsea Functions

Data Readback

Type

Size

Length

Low

Slow

Slow

Yes

Separated if desired

Hydraulic

Large

Short

Discrete piloted hydraulic

Moderately low

Slow

Fast

Yes

Separated if desired

Hydraulic

Moderately Large

Moderate

Sequential piloted hydraulic

Moderate

Slow

Fast

No

Separated if desired

Hydraulic

Small

Moderate

Direct electro- Moderate hydraulic

Very fast

Fast

Yes

Separated if desired

Hydraulic and electric or composite

Moderate

Long

Moderate

Very fast

Fast

Yes

Integral

Hydraulic and Small electric or composite

hydraulic

Multiplexed

Long

Direct Hydraulic System

Electro-Hydraulic Multiplex System

Electro-Hydraulic Multiplex System HYDRAULIC POWER UNT

ELECTRONIC COOLING / DECODING CONTROL INPUTS

MODEM

TOPSIDE

DISPLAY

UMBILICALS

SEA LEVEL

SUBSEA

ELECTRONIC LOGIC SOLENOID CONTROL VALVE TO REMOTE SENSOR

POWER SIGNAL

TO ACTUATOR DISCHARGE TOSEA OR RETURN TO SUFACE (OPTIONAL)

SUBSEA UMBILICAL TERMINATION

VALVES TO BE ACTUATED

ROTARY CHOKE VALVE

LINEAR GATE VALVE

Topsides Equipment(Under Construction) TOPSIDES EQUIPMENT

PRODUCTION HYDRAULIC POWER UNIT

SURFACE CONTROL CABINET

TOPSIDES UMBILICAL TERMINATION UNIT

SUBSEA CONTROL UMBILICAL

SUBSEA CONTROL UMBILICAL

SUBSEA CONTROL MODULE (SCM) Control Module

Subsea Control Module (SCM)

Subsea Electronics Module

Directional Control Valve

Interface Cards

Optical Modems

Hydraulic HP Intensifier

SUBSEA EQUIPMENT

SCM MOUNTING BASE

ASSEMBLY SUBSEA CONTROL MODULE (SCM)

SUBSEA CONTROL MODULE

SUBSEA CONTROL MODULE (SCM) Lifting and Lock Down Connection Upper part “Computer Intelligence” Unit Lower Part Pilot Control Valves

SCM Housing

Alignment Pins Fluids & Electrics Connecting Pins Locking Pin DIVERLESS SCM CONNECTION SYSTEM – With Connection pins at the base

Platform Junction Box

Master Control Station

Typical Diver installed layout

Hydraulic Power Unit

Flexible jumper

Flexible jumper

Umbilical Termination Assembly (UTA)

Subsea Control Module

Temperature transducers

Flexible jumper

Choke cables

Pressure transducers

Hard piping

Typical ROV installed layout Umbilical Termination Assembly UTA

Xmas Tree

Xmas Tree

Subsea Control Pod Pod Base

Temperature transducers

Pressure transducers

Choke cables

SCM

SCMs are usually mounted on the each Tree, but Developments will require some Control Functions on the Manifold (for valves there).

CHEMICAL INJECTION REQUIREMENTS CORROSION INHIBITOR If the reservoir fluids contain Hydrogen Sulphide or Carbon Dioxide, then these could cause corrision in normal steel lines. Inhibitors can be continuously injected to avoid the consequence of a corroded flowline. HYDRATES INHIBITOR To avoid hydrate formation in Pipelines / Flowlines, Xmas trees, Risers and export headers liquids like methanol, ethanol, LDHI or MEG are injected. The quantities will be relatively large. WAX & ASPHALTENES INHIBITOR Wax deposition in pipelines and risers can have a significant effect on oil production efficiency. Build-up in pipelines can cause increased pressure drops, resulting in reduced throughput and thus reduced revenue. In more extreme cases, pipelines/processing facilities can plug, halting production and leading to potentially huge losses in earnings. Chemical Injection is one of the possible solutions SCALE INHIBITOR The precipitation of Scale and Salt is a serious problem and can block the flow path of hydrocarbons. Scale may be Barium Salts. Salt scaling is particularly severe in wells with high saline (>200 g/l) formation brines which may be near saturation with respect to sodium chloride. The phenomena occurs more frequently in gas wells than in oil wells, and can be caused by low pressures, decreasing temperatures reservoir water constituents. EMULSION INHIBITOR The reservoir fluids often contain soap like chemicals naturally. These can form emulsions between the oil and water molecules. These give rise to flow and separation problems.

CHEMICAL INJECTION REQUIREMENTS

DRILLING CONTROL SYSTEM