Subsea High-speed Control System - Closing the Control ... - Zlatan Kobslic.pdf · Subsea...

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© 2008 Aker Solutions

Subsea High-speed Control System - Closing the Control Loop Subsea

04.06.2008Zlatan Kobaslic

© 2008 Aker Solutions part of Aker

DeepBoosterTM

■ Highly effective booster in deep water ■ Remove / reduces slugging problems■ Improves hydrate prevention■ Enables split flow to different hosts

(Deep water) gas/liquid separation and liquid pumping


Deep Booster field


Deep Booster Qualification Program

Deep Booster general arrangement drawing

Deep Booster Process Flow Diagram

Qualified previously– Separator (CCD)– Liquid Booster (LB)– Recycle valve– Subsea computer (SEM):

standard AS SEM

Qualification through Deep Booster– DB control system– DB system solution including all

sub-components


High-speed Control System – Main Components

treetree

Sea Level

Multiphase Flowline

GasRiser

Gas- LiquidSeparator

ProductionManifold

X-masX- mas

X-mastree

X- mastree

LiquidRiser

Topsides

Gas – Liquid Separator

Re- cycle valveSEM

MCS

Liquid PumpSubsea

Instrumentation

Process HPU VSD

Lube oil / Hydraulic power

Power supply


Power supply

Control signal

HPU Hidraulic Power UnitMCS Master Control StationVSD Variable Speed DriveSEM Subsea Electronic Module

1. High-speed Control Valve (stepless)Operation time 0-100% <2sec

LT

2. Subsea Electronic Module with implemented software: PID controllers with logic / DeadBand / GainSchedulig

3. Level Transmitter (DPT) with low response time <1 sec

Deep Booster Layout


Control System: Conventional vs. Deep Booster solution

Conventional solutionControl logic implemented and closed topside. System requirements: >3 sec

Deep Booster solutionControl logic implemented and closed subsea. System requirements: <3 sec


Control Loop Closed Topside (Conventional Solution)

Control logic implemented and closed topside (MCS)Separator Level Control acting on pump speed from topside controller via VSDLB Min Flow Control acting on recycle valve from topside controller


Well fluid

Liquid Booster

Recirculationcontrol valve (closed)

FT

Control Loop Implemented & Closed Topside (Conventional Solution)

Gas Liquid

Liquid

Large Volume Separator

LT SEM

Slugging Entering Separator

1. Separator Level Control

3. Process Dynamics: 1-20min

VSDMCS

2. Controller is adjusting pump speed in order to hold the separator level close to the setpoint


Well fluid

Liquid Booster

Recirculationcontrol valve

Control Loop Implemented and Closed Topside (Conventional Solution)

Gas Liquid

Liquid

Large Volume Separator

LT

VSD

1. LB Min Flow Control

3. Process Dynamics: 5-15secFT

MCS

Reducing of separator inflow or slugging SEM

2. Controller is opening recyclevalve in order to increasepump flow over the pump min flow limit


Control Loop Implemented and Closed Subsea (DB)Control logic implemented and closed subsea (SEM)

treetree

Sea Level

Multiphase Flowline

GasRiser

Gas- LiquidSeparator

ProductionManifold

X- masX- mas

X- mastree

X- mastree

LiquidRiser

Topsides

Gas – Liquid Separator

Re- cycle valveSEM

MCS

Liquid PumpSubsea

Instrumentation

Process HPU VSD


Power supply


Power supply

Control signal

HPU Hidraulic Power UnitMCS Master Control StationVSD Variable Speed DriveSEM Subsea Electronic Module

Separator Level Control (quick level variations) acting on recycle valvefrom high speed controller – LB speed unchangedPump Minimum Flow Control acting on recycle valve from high speed controller

Control logic implemented and closed topside (MCS)Re-cycle valve optimal position controller acting on pump speed from the topside controller – getting recycle valve back to optimal opening (15%). This controller will cover slow level variation over longer period of time(e.g.days/weeks)


LT

Well fluid

LiquidBooster

Recirculationcontrol valvepartly continuous open

FT

Control Loop Closed and Implemented Subsea (DB)

Slugging Entering Separator

CCD

Gas Liquid

1. Separator Level Control(quick level variations )

2. Process Dynamics: 3-10sec

3. LB min Flow Control4. Process Dynamics: 2-5sec

ZT

5. Re-cycle valve optimal position controller (coarse level var.)

6. After longer period of time the recycle valve will be operating at the certain opening ex. 38%.

7. In order to get it back to its optimal opening (ex. 15%) the topside controlleris acting on pump speeddecr. pump speed level incr. valve closing

SEM

MCS VSD


Test loop

LT

FT

SEM

MCS

VSD

Re-cyclevalve

Liquid Booster

SeparatorCCD

Liquid SupplyPump

Slug generation

velveLiquid Outlet

Re-cycle fluid

CCD liquid outlet

CCD gas outlet

Water filled test-pit

Mechanichal regulator


High-speed controller: Main components used in test

Subsea Control Valve (Steplees)Subsea qualified 3000mBiffi actuator / Kent Introl valveHydraulic operatedCommunication: ModBus / RS485Response time: 0 – 100% open 1,73 secPreviously qualified through test: 1 million cycles

Subsea Electronic Module (SEM)Subsea Qualified 3000mStandard Aker Solutions SEM

Differential Pressure Transmitter SDP-6Subsea qualified 3000mRead MatreRemote SealsCommunication: ModBus / RS485Response time: <1s


Test Program

Conventional Solution (Large Separator). Control logic implemented topside

Deep Booster System Test (CCD) Subsea high-speed controller. Control logic implemented subsea and topside


Test program: Conventional Solution (Large Separator)

Introduction to the Deep Booster system test (Conventional solution with large separator)

Control logic implemented and closed topside

Basis taken from planed subsea process installation (scaled down with respect to flow)

The following operation mode were covered:Normal productionNormal production including steady-state sluggingTurndown productionTurndown production including turndown slugging

The results of the only most relevant cases are shown in this presentation


Test results: Conventional Solution (Large separator)CASE 2 and 6 / Year 5Normal Production – Turn down production – Normal Production Separator inflow decreasing / increasing: 54,44m3/h – 22,58 m3/h – 54,44m3/hNo alarms / trips activated during the test


Test results: Conventional Solution (Large separator)CASE 11 / Year 2Turn down product. – Turn down slugging – Turn down product.Separator inflow: 18,82m3/h–Turn down slugging (54m3/h-13m3/h)-18,82m3/hNo alarm / trips activated during the tests


Test program – Deep Booster System Test (CCD)

Deep Booster system test (High-speed Control System Test – Closing the control loop subsea in addition to topside). Vertical gas/liquid separator used CCD (Compact Cyclonic De-gaser)

Control logic implemented and closed subsea/topside

Basis taken from planed subsea process installation (scaled down with respect to flow)

The following operation mode were covered:Increasing / Decreasing of the CCD flowSystem influenced with the small slugsSystem influenced with the medium slugsSystem influenced with the large slugs

The results of the only most relevant cases are shown in this presentation


Test results: Deep Booster System Test

CASE 3-2-1Increasing / Decreasing of CCD flowCCD flow: A-25% decreasing / B-35% decreasing / C-52% decreasing of initial flowNo significant change of the CCD level during flow variations observedNo alarms/trip activated during the test


Test results: Deep Booster System TestCASE 3-2-4System influenced with large slugsCCD flow: initial:42,47m3/h – slug high:71,12m3/h – slug low:14,28m3/hAll level variations were taken by re-cycle valve and no significant CCD level changes observedNo alarms/trip activated during the test


Conclusion Qualification Program

During all tests cases no instabilities in the pump speed were seenIn all test cases the control system was able to handle disturbances caused when the system was influenced by different types disturbancesAll CCD level variations were initially taken by the high-speed controller (acting on recycle valve)Small and moderate slugs are not causing CCD liquid level to oscillate when the High-speed control system solution is used (Control loop closed subseain addition to closing topside)By introducing of the deadband in the controllers (measuring) the system can handle small and even moderate slugs with constant recycle valve position and constant LB speed over longer period

The system can handle turndown production – separator inflow is lower than the LB min flow limit (min. flow controller is regulating pump flow)

The system can handle huge amount of gas entering the CCD, without causing larg drop in CCD level (no alarms / trip initiated)


High-speed Control System – Application Area 1

Subsea Compression: Anti-surge controlProcess dynamics: 0,5 – 2 seconds



Liquid-liquid cyclone flow split controlProcess dynamics: 1 – 5 seconds



Separator (CCD) liquid level and pump minimum flow control (DeepBooster)Process dynamics: 3 – 10 seconds


Deep Booster - An Efficient Solution For the Deep Water Fields

Fully subsea qualified: 3000mHighly effective booster in deep water fields Efficient combination of separation & boosting – energy addingImprove hydrate preventionRemoving / reducing slugging problemsEnable split flow to different hostsFully condition monitoring of all components is available All main components pumps, CCD, recycle valve, electronic module are separately retrievableThe main control philosophy behind the Deep Booster is to primary use the recycle valve during the rapid separator liquid variations / slugging. This will significantly extend the Liquid Booster lifetime and reduce a need for the pump maintenance. Introducing a dead band in a measuring in the controllers will make system able to operate with constantly open recycle valve and pump running with the constant speed. That means that we will allow the separator liquid level to vary (within some predefined limits) without changing the recycle valve position or/and the pump speed. This will again significantly extend the recycle valve lifetime and reduce a need for its maintenance. Including a condition monitoring into the whole installation will make operator able to predict possible failures and plan the component replacements in advance. This will strongly reduce the down time during the maintenance.


Disclaimer

This Presentation includes and is based, inter alia, on forward-looking information and statements that are subject to risks and uncertainties that could cause actual results to differ. These statements and this Presentation are based on current expectations, estimates and projections about global economic conditions, the economic conditions of the regions and industries that are major markets for Aker Solutions ASA and Aker Solutions ASA’s (including subsidiaries and affiliates) lines of business. These expectations, estimates and projections are generally identifiable by statements containing words such as “expects”, “believes”, “estimates” or similar expressions. Important factors that could cause actual results to differ materially from those expectations include, among others, economic and market conditions in the geographic areas and industries that are or will be major markets for Aker Solutions’ businesses, oil prices, market acceptance of new products and services, changes in governmental regulations, interest rates, fluctuations in currency exchange rates and such other factors as may be discussed from time to time in the Presentation. Although Aker Solutions ASA believes that its expectations and the Presentation are based upon reasonable assumptions, it can give no assurance that those expectations will be achieved or that the actual results will be as set out in the Presentation. Aker Solutions ASA is making no representation or warranty, expressed or implied, as to the accuracy, reliability or completeness of the Presentation, and neither Aker Solutions ASA nor any of its directors, officers or employees will have any liability to you or any other persons resulting from your use.Aker Solutions consists of many legally independent entities, constituting their own separate identities. Aker Solutions is used as the common brand or trade mark for most of these entities. In this presentation we may sometimes use “Aker Solutions”, “we” or “us” when we refer to Aker Solutions companies in general or where no useful purpose is served by identifying any particular Aker Solutions company.

Subsea High-speed Control System - Closing the Control ... - Zlatan Kobslic.pdf · Subsea...

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