Survey of Experience with

Integrated Metocean and Structural

Integrity Monitoring

on 36 Deepwater ProductionSystems

Presenter: Thomas L. Johnson

Presentation Objectives

• Describe Integrated Metocean and Structural Integrity

for Deepwater Floating Production Systems

• Present the rationale for monitoring

• Give some examples of what is measured and how

the information is used

Typical Deepwater Floating Production Systems

Goals of Integrated Marine Monitoring

Systems (IMMS)

• Monitor “marine” parameters (as distinct from drilling

system parameters or process control parameters)

• To provide:

Real–time operational decision support

Archived data on a common time base for:

integrity management,

forensic analysis,

verification of engineering design tools.

Elements of Integrity Monitoring

Metocean

Motion Loads

Metocean (Floating structure forcing function)

• waves

• winds

• currents

Floating Structure Responses (examples)

• wave frequency motions (6 degree of freedom)

• position

• mooring/tendon tension

• riser loads and motions

• hawser loads

• hull bending stress

Rationale for Monitoring (following 4 slides in extended abstract)

Operational Decision SupportForensic

Engineering

Verification of Design

Tools

Integrity

Monitoring

Measurement Subsystem Installation Running Riser Drilling Production

Air Gap/Waves Not Functional Guidance on managing service vessel, crane and heavy lift operations

Estimate Run-Up; Assess

wave damages;

Characterize environment

Characterize Environmental forcing

functions

Input to Damage

Prediction Models

Wave Direction Not Functional Guidance on managing service vessel, crane and heavy lift operations

Estimate Run-Up; Assess

wave damages;

Characterize environment

Characterize Environmental forcing

functions

Input to Damage

Prediction Models

Wind Speed and Direction Not FunctionalGuidance on managing Helicopter,service vessel, crane and heavy lift

operations

Assess Topsides

damage;Characterize

environment

Characterize Environmental forcing

functions

Input to Damage

Prediction Models

"Surface Current"Guidance on managing

service vessel operationsGuidance on managing service vessel operations

evaluate cause of mooring

failures or observed platform

Vortex Induced Motion

Characterize Environmental forcing

functions-Validate Hull VIM Models

Input to Damage

Prediction Models

Current ProfileGuidance on managing

subsea operations

Identify excessive

currents

Identify excessive

currentsN/A

Determine cause of riser

loads

Characterize Environmental forcing

of risers

Input to Fatigue

Damage Prediction

Models

Bottom Current (Profile)Guidance on managing

subsea operations

Identify excessive

currents

Identify excessive

currentsN/A

Determine cause of riser

loads

Characterize Environmental forcing

of risers

Input to Fatigue

Damage Prediction

Models

Pressure/Temperature/Humidity Not FunctionalAdvance storm forecasting for Helicopter,service vessel, crane and

heavy lift operations

Verify hurricane/storm

intensityN/A N/A

Platform Attitude and Motions (0.0

and 0.01 Hz -1Hz)

TLP- check trim and list

prior to tendon lock-off to

ensure platform installed

level

Guidance on managing heavy lift operationsEstimate excitation of

SCR's and production risers Verify Global Motion Models

Estimate Fatigue

damage in SCR's;

Foundations of Large

tanks/Derrick

Platform Position and Motions (0.00

Hz -0.01Hz)-within 150 Nautical Miles

of USCG Stations

Check Mooring Set Up

and on SCR's to verify

installed angle

Positioning Platform over subsea well heads

Mooring System

Adjustment in

Anticipation of weather

or high curents

Estimate excitation of

SCR's and Production

Risers, Mooring loads

Verify Global Motion Models; VIM

Models

Quasi static loads

on Mooring

Equipment

Platform True Heading (Low

frequency yaw)

Check As Installed

Heading and on SCR's to

verify installed angle

Positioning Platform over subsea well heads Mooring System

Adjustment

Estimate excitation of

SCR's Verify Global Motion Models

Estimate excitation

of SCR's

Production Riser Tensions and

Bending Moments Not Functional Set Riser Tension

Manage riser tension

factor

Manage riser tension

factor

identfy performance

problems

Verify Riser Responses and fatigue

models

Riser Fatigue

Damage

Production Riser Stroke Not Functional Not Functional N/AWarn of Approach to

Stops

identify excessive riser

excursions; identify failure of

B Cans to slip in guides

Verify Riser Quasi Static

Responses N/A

Air Can pressures Not Functional Set TensionMaintain Tension and

Identify sources of leaksExplain Tension Loss N/A

Track integrity of

chambers

Air Can Riser Guide Compression Not Functional N/A N/A N/AAssess loads on Buoyancy

CansAssess Load Estimation Models N/A

Tendon Tensions Set Tensions N/A N/AMaintain Tension and

Weight Distributioninvestigate tendon failures

Validate Tendon Tension Estimating

Models

insure that CG is

within proper limits;

identify degradation

in tendon anchors

Mooring Line Tensions and Payout Set TensionsPositioning over

subsea wellheads

Positioning over

subsea wellheads

Tension Adjustment for

high currents and

Hurricanes

Identify causes of Mooring

Failures and quantify time-

on-link for fatigue estimation

Verify Global Motion Models

Track mooring line

fatigue damage;

anchor failures

DraftTLP- use to verify

installed tendon tensionsN/A N/A Ballast/Trim/Heel Control

establish causes of errors in

ballast controlRequired for chracterization of hull

Identify sinkage due

to leaks/collision

damage

Ballast Tank LevelsTLP- use to verify

installed tendon tensionsN/A N/A Ballast Trim Heel Control

establish causes of errors in

ballast controlRequired for chracterization of hull

Track Intact and

Damaged Stability

Steel Catenary Riser

Inclination/Vibration

Verify SCR Installed

inclinationN/A N/A N/A

help to identify reasons for

component filure or

degradation

verify Floater Motion induced

response in SCR

Estimate and Track

SCR Fatigue

Rationale Matrix • Operational Decision Support (installation, riser running, drilling, production)

• Forensic Engineering

• Verification of Design Tools

• Integrity Management

• Air Gap measurements

• Wind speed and direction measurements

• Current measurements

• Platform 6 degree of freedom motions / position measurements

• Mooring load measurements

• Riser strain, tension, bending and motion measurements

• Ballast level measurements

• etc.

mapped onto

Measurement Subsystem

Typ

e

Sem

i-su

bm

ers

ible

TL

P

Cla

ssic

Sp

ar

Tru

ss S

pa

r

Tru

ss S

pa

r

Tru

ss S

pa

r

Cell S

pa

r

TL

P

TL

P

Sem

i-su

bm

ers

ible

Tru

ss S

pa

r

Tru

ss S

pa

r

Tru

ss S

pa

r

TL

P

Sem

i-su

bm

ers

ible

Sem

i-su

bm

ers

ible

Air Gap/Waves

X (4) X (3) X (2) X (4) X (2) X (2) X (2) X (4) X (4) X (2) X (4) X (4) X (4) X (4)

Wave Direction X

Wind Speed and Direction

X (2) X (2) X (2) X (2) X (2) X (2) X (2) X (2) X (2) X (2) X (2) X (2) X (3) X (2)

"Surface Current"

X (2) X X X (2) X X X X X X

Current Profile X X X X X X X X X X X X

Pressure/Temperature/Humidity X X X X X X X X X X X

Platform Attitude and Motions (0.01 Hz -

1Hz) X X X X* X X X X X X X X X

X (2

DOF) X X

Platform Position and Motions (0.00 Hz -

0.01Hz) X (2) X X X (2) X X X X (2) X (2) X (2) X (2) X (2) X (2) X X

Platform True Heading X X X X X X Production Riser Tensions and Bending

Moments (Integral Air Can )

Production Riser Tensions and Bending

Moments ("Free" Air Can ) X X X X

Production Riser Tensions (Hydro-

pneumatic Tensioners) X X

Production Riser Stroke

X (15) X (4) X (4)

Riser and Pull Tube Monitoring Air Can Buoyancy Force X Air Can Riser Guide Compression X Tendon Tensions (TLP's only) X X X X Steel Catenary Riser

Inclination/Vibration X X X

Long Base Strain Gauges Hybrid Riser Tower Monitoring System Calm Buoy/OOL Monitoring System Independent Remote Monitoring System

(IRMS) X X X X X X X X X X X X X

Mooring Line Tensions X X X X X X X X X X

Draft X X X X X X X X X X X X X X

Ballast Tank Levels X X X X X X X X X X X X X

Measurement Subsystem

Typ

e

Se

mi-s

ub

me

rsib

le

Cla

ss

ic S

pa

r

Tru

ss

Sp

ar

TL

WP

TL

P

TL

P

Tru

ss

Sp

ar

Se

mi-s

ub

me

rsib

le

Tru

ss

Sp

ar

Se

mi-s

ub

me

rsib

le

Tru

ss

Sp

ar

Sp

ar

TL

P

Air Gap/Waves

X (4) X-laser

(1) X (4) X (2) X (2) X (2) X(2) X (2) X (2) X (4) X (2)

Wave Direction X X X

Wind Speed and Direction X (2) X (2) X (2) X X X X X (2) X X (2) X (2) X (2) X (2)

"Surface Current" X X X X (2) X X

Current Profile X X X X X X X X X X X

Pressure/Temperature/Humidity X X X X X X X X X X X X X

Platform Attitude and Motions (0.01 Hz -1Hz)

X X X X X (5

DOF)

X (5

DOF) X X X X X

X (3

DOF)

Platform Position and Motions (0.00 Hz -0.01Hz)

X X X X (2) X (2) X X X X X X X

Platform True Heading X X X X X X

Production Riser Tensions and Bending

Moments (Integral Air Can ) X

Production Riser Tensions and Bending

Moments ("Free" Air Can ) X X X

Production Riser Tensions (Hydro-pneumatic

Tensioners) X X

Production Riser Stroke X

Riser and Pull Tube Monitoring X

Air Can Buoyancy Force

Air Can Riser Guide Compression

Tendon Tensions (TLP's only) X X X X

Steel Catenary Riser Inclination/Vibration

Long Base Strain Gauges

Hybrid Riser Tower Monitoring System

Calm Buoy/OOL Monitoring System

Independent Remote Monitoring System (IRMS)

Mooring Line Tensions X X X X X X X X

Draft X X X X X X X X X X

Ballast Tank Levels X X X X X X X X X

Measurement Subsystem

Typ

e

FP

SO

TL

P

TL

P

Tru

ss

Sp

ar

FP

SO

FP

SO

FP

SO

Air Gap/Waves X (2) X (4) X (4) X (2) X (2)

Wave Direction

Wind Speed and Direction X (2) X (2) X (2) X (2) X (2)

"Surface Current" X (2) X (2) X (2) X (2) X (2)

Current Profile X X X X

Pressure/Temperature/Humidity X X X X X

Platform Attitude and Motions (0.01 Hz -1Hz) X X X X X X

Platform Position and Motions (0.00 Hz -0.01Hz) X X X X X X

Platform True Heading X X X

Production Riser Tensions and Bending Moments (Integral Air Can )

Production Riser Tensions and Bending Moments ("Free" Air Can )

Production Riser Tensions (Hydro-pneumatic Tensioners) X X

Production Riser Stroke

Riser and Pull Tube Monitoring

Air Can Buoyancy Force

Air Can Riser Guide Compression

Tendon Tensions (TLP's only) X X

Steel Catenary Riser Inclination/Vibration

Long Base Strain Gauges X

Hybrid Riser Tower Monitoring System X X

Calm Buoy/OOL Monitoring System X

Independent Remote Monitoring System (IRMS)

Mooring Line Tensions X X X X

Draft X X X X

Ballast Tank Levels X X X X

Microwave Radar Air Gap Sensor

Operational Decision Support & Design Verification

Airgap Sensor derived Hs vs. NDBC wave buoy nearby

0

2

4

6

8

10

12

14

16

1-O

ct

7-O

ct

13-O

ct

19-O

ct

25-O

ct

31-O

ct

Sig

nif

ican

t W

ave H

eig

ht

Hs (

ft)

Hs (AirGap Sensor)

Hs (NDBC 42041)

Anemometer Installed on Crane Top

Operational Decision Support

Helideck Display (CAP 437 Compliant)

38 kHz ADCP Deep Current Profiler

ROV Deployable HADCP on Greater Plutonio FPSO

Outward Looking (Hybrid Riser Tower Acoustic

Positioning System shared the Fixture with the HADCP)

Bottom Mounted 75 kHz ADCP with acoustic modem in

approximately 4,500 ft of water near BP’s Mad Dog spar

Operational Decision Support (riser running, ROV Ops)

Typical screen plot of Combined Current Profile

Forensics, Design Verification & Integrity Management

Client Data Center (CDC)

Vortex Induced Motions (VIM) • Vortex-Induced Motions

(VIM) are motions induced

on large floating bodies

interacting with an external

fluid flow, produced by – or

the motion producing –

periodical irregularities of

this flow.

• VIM, if prolonged, could

cause riser and mooring

fatigue.

• VIM, when fully locked in,

could dramatically escalate

the drag loads on the

structure causing mooring

damage.

• Increased loading would

also cause increased

platform offset.

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

-0.2-0.10.00.10.20.30.4

Sway/D

Su

rg

e/D

D

A/D

Ur=UT/D

Figure 1: : A/D vs. Ur

Vortex shedding

Lock-in

Vessel Excursion

Source of VIM (Vortex Induced Motion)

Source: Ocean Remote Sensing Group, John Hopkins University Applied Physics Laboratory

Loop Current (max. boundaries)

Eddy Ulysses (Detached Eddy)

GoM Loop/Eddy current measurements

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 100 200 300 400 500 600 700 800 900 1000

Current Magnitude

De

pth

HADCP 03/16/05

Upper ADCP 03/16/05

Lower ADCP 03/16/05

Free Surface

Shear Current Profile

( )U U z

Source: BMT Scientific Marine Services

HADCP

A

D

C

P

Power spectral density plots (by day)

• Color indicates

higher/lower energy

• 100 to 300 seconds

typical mooring

horizontal natural

frequency

• Plots can be used to

quickly evaluate

whether VIM was likely

occurring

Example – 1 day of measured position data

Started with approx. 22

units of excursion

oscillation

Grew to 30 units of

excursion oscillation

Ended day with17 units of

excursion oscillation

Why is it important to investigate full scale VIM

responses?

Contrary to MMS workshop (held 22-24 October 2003) entitled “Spar

Vortex-Induced Motions” not only spars experience VIM.

However

• If VIM does not occur as frequently or

• VIM does not have the expected magnitude

Then

• May be over-designing moorings and risers substantially

Next question

• Why is it not as big or frequent?

BMT High Precision Static and Dynamic Subsea

Inclinometer in ROV Receptacle on Holstein Spar SCR

BMT Subsea Inclinometer-in service 4 years fault free at -500 feet

BMT High Precision Static and Dynamic Subsea

Inclinometer (4 Degree of Freedom Inertial Package)

Comparison of Imposed and Measured Inclination

(actual spar inclination record used for test)

Impact of Tropical Storm on Mooring Tension

Semi-log TS Plot of Mooring Fatigue Damage

Detail – Why Accumulated Fatigue Jumped

60

55

50

45

40

35

30

25

20

Thank you