Integrated Marine Monitoring System

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IBP3407_10
REVIEW OF FLOATING PRODUCTION PLATFORM REAL-TIME
INTEGRITY MONITORING SYSTEMS WORLDWIDE
Craig Campman1, Roderick Edwards2, William “Bud” Hennessy3
IBP3407_10
Copyright 2010, Brazilian Petroleum, Gas and Biofuels Institute - IBP
This Technical Paper was prepared for presentation at the Rio Oil & Gas Expo and Conference 2010, held between September, 1316, 2010, in Rio de Janeiro. This Technical Paper was selected for presentation by the Technical Committee of the event according to
the information contained in the abstract submitted by the author(s). The contents of the Technical Paper, as presented, were not
reviewed by IBP. The organizers are not supposed to translate or correct the submitted papers. The material as it is presented, does
not necessarily represent Brazilian Petroleum, Gas and Biofuels Institute’ opinion, nor that of its Members or Representatives.
Authors consent to the publication of this Technical Paper in the Rio Oil & Gas Expo and Conference 2010 Proceedings.
Abstract
A technical description of environment, response and integrity monitoring systems that are currently deployed
on floating production platforms offshore Brazil, West Africa, Malaysia, and in the Gulf of Mexico is presented. The
rationale for making each of the measurements and the measurement approach is described. The paper summarizes the
system capabilities, describes the measurements and sensors, as well as discussing the presentation of the real-time
information to the production operators, and the analysis options for the stored data collected by the systems. In
addition to offshore data collection, an automated onshore data transfer, data management, and analysis capabilities are
presented. Selected, noteworthy, measurement technologies are discussed including very high accuracy motion
measurement systems for low motion platforms, high resolution/band width riser tension and bending moment sensing
systems, tendon tension monitoring, SCR top static and dynamic response measurement, wave measurement from
platforms and current profiling from the platforms. Shore-side networking with the offshore monitoring systems is also
described, and automated daily reports and monthly reports from these platforms are presented.
Systems profiled will range from the first application of this technology in the Gulf of Mexico in 1987, through
mooring monitoring systems installed offshore Brazil starting in 2001, to more recent installations on facilities
worldwide.
The focus of the discussions of this paper will be on “marine” monitoring systems on platforms with which
BMT has had sufficient involvement to permit the authors to speak knowledgeably about their particulars. Topics to be
covered in the paper will include:
• Objectives of the IMMS/ Systems – Systems that monitor “marine” parameters as distinct from drilling
system parameters or process control parameters. They provide real –time operational decision support
and archived data on a common time base for integrity management, forensic analysis, and verification of
engineering design tools.
• Operational Decision Support - The primary function of these systems is to provide real-time information
in an easy to understand format to the platform operators.
• Forensic Engineering - The process of establishing the cause of accidents, equipment failures, storm
damage, lower than expected subsystem performance and identifying remedial action.
• Integrity Monitoring - Maintain a continuous, real time picture shore side of the “health” of critical
elements of the facility.
• Evaluation of the impact of episodic events.
• Support estimates of the remaining fatigue life in facility components.
Discussion of various monitoring system components will describe the sensor types and measurements
recorded in the systems installed offshore. Measurements discussed will include:
• Wave Estimation—air gap measurement subsystem.
• Current Monitoring - surface to platform keel, platform mounted deep profiles, and bottom current
profiles.
• Riser Top Tension Measurement Sub System
______________________________
1
Senior Project Mgr., Instrumentation Systems – BMT SCIENTIFIC MARINE SERVICES
2
Vice President Business Development – BMT SCIENTIFIC MARINE SERVICES
3
Vice President – Instrumentation Systems – BMT SCIENTIFIC MARINE SERVICES
Rio Oil & Gas Expo and Conference 2010
1. Introduction
We shall discuss monitoring systems, the primary purposes of which are to provide information support to
platform operators and to facilitate long term integrity monitoring of the “marine” systems. The first such system in
which the personnel of BMT Scientific Marine Services Inc were involved was for the CONOCO Joliet TLWP in 1987.
This is described in Peters D.J.H et al 1990 [1]. Since that time, these systems have evolved into comprehensive
packages with operator friendly, real time features in addition to reliable archiving of data for later analysis and realtime connections to the shore. Shell Oil Company followed the Joliet Performance Monitoring System with the ground
breaking Auger Performance Monitoring Instrumentation System described by Denison et al 1990 [2]. Subsequent Shell
TLPs (Mars, Ram Powell, Ursa, and Brutus) were equipped with similar systems that were somewhat reduced in scope.
The focus of the discussions of this paper will be on “marine” monitoring systems on platforms that have been
installed since 1997 and with which BMT has had sufficient involvement to permit the authors to speak knowledgeably
about their particulars. We shall refer to these systems collectively henceforth as Integrated Marine Monitoring Systems
(IMMS). Tables 1, 2 and 3 list the platforms in the Gulf of Mexico, Offshore West Africa, Brazil and Malaysia that will
be discussed in this paper. The tables identify the platforms by name, owner, location, and/or main contractor for the
design, and summarizes the measurements that are made on these platforms. These tables have been expanded to
include new installations worldwide since the publication of Edwards, R.Y.et al 2005 [3].
Table 1. Summary Table of Gulf of Mexico Floating Production Platforms equipped with BMT Integrated Marine
Monitoring Systems – Part 1
Gulf of Mexico
BP/ABBL G
BP/Technip
BP/Technip
BP/Technip
Gulf of Mexico
Semisubmersible
Mariin (TLP)
Mad Dog (Truss Spar)
Horn Mountain (Truss Spar)
Holstein (Truss Spar)
Semisubmersible
Semisubmersible
X (2)
X (4)
X (4)
X (2)
X (4)
X (4)
X (4)
X (2)
X
X
X
X (2)
X
X
X (2)
X
X
X
X (2)
X (2)
X (3)
X
X
X (2)
X
X
X
X
X
X
X
X
X
X
X
X
X
X (2
DOF)
X (2)
X (2)
X (2)
X (2)
X (2)
X (2)
X
X
X
X (2)
X
X
X
X
Gulf of Mexico
X (2)
X (2)
X
X
X
X*
X
TLP - Seastar™
X (2)
X (2)
X
X
X
X
X
Gulf of Mexico
X
Red Hawk (Cell Spar)
X
Anadarko/Technip
X (4)
X
X (2)
X (2)
X
X (2)
X
Nansen (Truss Spar)
X
Anadarko/Technip
X
Gunnison (Truss Spar)
X (2)
X (2)
X
X
Anadarko/Technip
X (3)
X (2)
X
Boomvang (Truss Spar)
X (4)
X (2)
X (2)
X
X
Anadarko/Technip
NEPTUNE (Spar)
Platform True Heading
Anadarko
Platform Position and Motions (0.00 Hz -0.01Hz)-within 190
Nautical Miles of USCG Stations
Platform Position and Motions (0.00 Hz -0.01Hz)-beyond
190 Nautical Miles of USCG Stations
Marco Polo (TLP)
Platform Attitude and Motions (0.01 Hz -1Hz)
Anadarko
Name/Type
Air Gap/Waves
Wave Direction
Wind Speed and Direction
"Surface Current"
Current Profile
Pressure/Temperature/Humidity
Independence Hub (Semisubmersible)
Owner/
Contractor/Location
Measurement Subsystem
Anadarko
US Domestic
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
Production Riser Tensions (Hydro-pnuematic Tensioners)
X
X
X
X
X (4)
X (4)
X
Production Riser Stroke
Riser and Pull Tube Monitoring
Air Can Buoyancy Force
X (15)
X
Air Can Riser Guide Compression
Tendon Tensions (TLP's only)
X
X
Steel Catenary Riser Inclination/Vibration
X
X
X
X
X
X
X
X
X
X
X
X
X
Fiber Optic Long Base Strain Gauges
Hybrid Riser Tower Monitoring System
X
X
X
X
X
X
X
X
Calm Buoy/OOL Monitoring System
Ballast Control System
Independent Remote Monitoring System (IRMS)
Mooring Line Tensions
Draft
Ballast Tank Levels
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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Rio Oil & Gas Expo and Conference 2010
Table 2. Summary Table of Gulf of Mexico Floating Production Platforms equipped with BMT Integrated Marine
Monitoring Systems – Part 2
Matterhorn (TLP-Seastar™)
X (2)
X (2)
X (4)
X (2)
X (2)
X (2)
X
X
X
X
X
X
X
X (2)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X (5
DO
F)
X (5
DOF)
X
X
X
(2)
X (2)
X (2)
X (2)
X
X
X
X (2)
X
X
X
X
X (2)
X
X
X
X
X
X
X
X
X
Production Riser Tensions and Bending Moments (Integral
Air Can )
X
X
X
X
X
X
X
X
X
X (2)
X
X
X (3
DOF)
X
X
X (MS860)
X
X
Production Riser Tensions and Bending Moments ("Free"
Air Can )
X
Production Riser Tensions (Hydro-pnuematic Tensioners)
X
Production Riser Stroke
Riser and Pull Tube Monitoring
Air Can Buoyancy Force
Air Can Riser Guide Compression
Tendon Tensions (TLP's only)
W&T/Atlantia
Spar
X(2)
X (2)
X
X
X
X
Gulf of Mexico
Medusa (Truss Spar)
X (2)
X
X
X
X
X
X
Murphy/McDermott
Semisubmersible
Devils Tower (Truss Spar)
X (2)
Gulf of Mexico
ENI/McDermott
Morpeth (TLP-Seastar™)
X
(2)
Front Runner(Truss Spar)
ENI/Atlantia
Allegheny (TLP-Seastar™)
X (4)
Murhpy/McDermott
ENI/Atlantia
Joliet (TLWP)
X-laser
(1)
Opti
Conoco/COP JIP
Typhoon (TLP-Seastar™)
X (4)
Gulf of Mexico
Chevron/Atlantia
Spar
Platform True Heading
Gulf of Mexico
Platform Position and Motions (0.00 Hz -0.01Hz)-within 190
Nautical Miles of USCG Stations
Platform Position and Motions (0.00 Hz -0.01Hz)-beyond
190 Nautical Miles of USCG Stations
Genesis (Classic Spar)
Platform Attitude and Motions (0.01 Hz -1Hz)
Chevron/Spartec
Name/Type
Air Gap/Waves
Wave Direction
Wind Speed and Direction
"Surface Current"
Current Profile
Pressure/Temperature/Humidity
Semisubmersible
Owner/
Contractor/Location
Measurement Subsystem
Gulf of Mexico
US Domestic
X
X
X
X
X
X
X
Steel Catenary Riser Inclination/Vibration
Fiber Optic Long Base Strain Gauges
Hybrid Riser Tower Monitoring System
Calm Buoy/OOL Monitoring System
Ballast Control System
Independent Remote Monitoring System (IRMS)
Mooring Line Tensions
Draft
Ballast Tank Levels
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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Rio Oil & Gas Expo and Conference 2010
Table 3. Summary Table of Floating Production Platforms in Brazil, Malaysia, and West Africa, equipped with
BMT Integrated Marine Monitoring Systems
Husky/SBM-A
P-52 (FPSO)
White Rose (FPSO)
X (4)
X (2)
X (2)
X (2)
X (2)
X
X
X
X (2)
X (2)
X
X
X
X (2)
X (2)
X
X
X
X (2)
X (2)
X (2)
X (2)
X
X
X
X
X
X
Espadarte (FPSO)
Petrobras
Truss Spar
Petrobras/SBM
Malaysia
TLP
X (4)
West Africa
TLP
Platform True Heading
X (2)
West Africa
Name/Type
Air Gap/Waves
Wave Direction
Wind Speed and Direction
"Surface Current"
Current Profile
Pressure/Temperature/Humidity
Platform Attitude and Motions (0.01 Hz -1Hz)
Platform Position and Motions (0.00 Hz -0.01Hz)-within 190
Nautical Miles of USCG Stations
Platform Position and Motions (0.00 Hz -0.01Hz)-beyond
190 Nautical Miles of USCG Stations
Greater Plutonio (FPSO)
Owner/
Contractor/Location
Measurement Subsystem
BP
International
X
X
X
X
X
X
X
X
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-pnuematic 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
Fiber Optic Long Base Strain Gauges
X
Hybrid Riser Tower Monitoring System
X
Calm Buoy/OOL Monitoring System
X
Ballast Control System
Independent Remote Monitoring System (IRMS)
Mooring Line Tensions
Draft
Ballast Tank Levels
X
X
X
X
X
X
X
X
X
X
X
2. Objectives of the IMMS
Integrated Marine Monitoring Systems (IMMS) monitor “marine” parameters as distinct from Drilling System
parameters or Process Control parameters. They provide real-time operational decision support and archived data on a
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Rio Oil & Gas Expo and Conference 2010
common time base for integrity management, forensic analysis, and verification of engineering design tools. The
rationale for the measurement systems included in an IMMS are summarized in Table 4 and discussed in general terms
in the following sections.
Table 4. Overview of the Rationale for IMMS Measurements
F o re n s ic
E n g in e e rin g
V e rific a tio n o f D e s ig n
T o o ls
In te g rity
M o n ito rin g
G u id an c e on m a na g in g s e rvic e ve s s e l, c ran e a nd h ea vy lift o pe ra tion s
E s tim a te R u n -U p; A s s e s s
w a ve d am a g es ;
Ch a ra c t eriz e en viro nm e n t
C h a ra c t eriz e E n viro nm e n ta l forc ing
fun c tio ns
In p ut to D a m ag e
P red ic tion M o de ls
G u id an c e on m a na g in g s e rvic e ve s s e l, c ran e a nd h ea vy lift o pe ra tion s
E s tim a te R u n -U p; A s s e s s
w a ve d am a g es ;
Ch a ra c t eriz e en viro nm e n t
C h a ra c t eriz e E n viro nm e n ta l forc ing
fun c tio ns
In p ut to D a m ag e
P red ic tion M o de ls
C h a ra c t eriz e E n viro nm e n ta l forc ing
fun c tio ns
In p ut to D a m ag e
P red ic tion M o de ls
In p ut to D a m ag e
P red ic tion M o de ls
O p e ra tio n a l D e c is io n S u p p o rt
M e a s u re m e n t S u b s y s te m
In s ta lla tio n
A ir G a p/ W aves
N o t F u n c t io na l
W a ve D ire c t ion
N o t F u n c t io na l
R u n n in g R is e r
D rillin g
P ro d u c tio n
W ind S p ee d a nd D irec tion
N o t F u n c t io na l
G u id an c e o n m a na g in g H elic op te r, s e rvic e ve s s e l, c ran e an d h ea vy lift
op e ra tio ns
A s s e s s To ps id es
da m a ge ;C h arac te riz e
e nviro n m en t
"S urfa c e C u rren t"
G u id an c e on m a n ag in g
s e rvic e ve s s e l o p erat io ns
G uid a nc e o n m an a gin g s ervic e ves s e l op e ra tio n s
e valu a te c au s e of m o oring
fa ilu re s o r o b s e rved p la tform
V o rt ex In d uc e d M ot io n
C h a ra c t eriz e E n viro nm e n ta l forc ing
fun c tio n s -V a lida te H u ll V IM M o de ls
C u rren t P rofile
G u id an c e on m a na g in g
s u bs e a op e ra tio ns
B ot to m C u rre n t (P rofile )
G u id an c e on m a na g in g
s u bs e a op e ra tio ns
P re s s u re /Tem p erat ure/ H um idit y
N o t F u n c t io na l
P la tfo rm A ttitu de a n d M ot ion s (0 .0
a n d 0. 01 H z -1 H z )
TLP - c h e c k t rim an d lis t
prio r t o te nd o n lo c k -o ff to
en s ure plat fo rm ins ta lle d
le ve l
Id e nt ify e x c e s s ive
c u rren ts
Ide nt ify e x c e s s ive
c u rren ts
N/ A
D et erm in e c a us e o f ris er
lo ad s
C h a ra c t eriz e E n viro nm e n ta l forc ing
of ris e rs
Id e nt ify e x c e s s ive
c u rren ts
Ide nt ify e x c e s s ive
c u rren ts
N/ A
D et erm in e c a us e o f ris er
lo ad s
C h a ra c t eriz e E n viro nm e n ta l forc ing
of ris e rs
A dvan c e s t orm fo re c as tin g fo r H e lic op te r, s e rvic e ve s s e l, c ran e a nd
h ea vy lift o pe ra tion s
V e rify hu rric an e /s to rm
in te n s it y
N /A
N /A
G uida n c e o n m an a ging he a vy lift op erat io ns
E s tim at e ex c ita tio n o f
S C R's an d prod u c t io n ris e rs
V e rify G lob a l M o tion M o d els
E s t im at e F at igu e
da m ag e in S C R 's ;
F o u nd a tio n s of La rg e
ta nk s /D erric k
E s tim at e ex c ita tio n o f
S C R 's a nd P rod uc tion
Ris e rs , M oo ring lo a ds
V erify G lo b al M o tio n M o de ls ; V IM
M od e ls
Q u a s i s ta tic lo a ds
o n M o orin g
E q u ipm e n t
E s tim at e ex c ita tio n o f
S C R 's
V e rify G lob a l M o tion M o d els
E s tim a te e x c it at io n
o f S C R 's
P lat fo rm P o s itio n a nd M o tion s (0 .0 0
H z -0 .0 1 H z )-w ith in 1 5 0 Na u tic a l M iles
o f U S C G S t at io ns
C h ec k M o orin g S e t U p
a n d on S C R 's to verify
ins ta lled a ng le
P os it io ning P la tform o ve r s u bs e a we ll h ea ds
P la tfo rm True H e ad in g (L o w
freq u en c y y a w )
C h ec k A s In s t alle d
He a ding a n d on S C R 's to
ve rify in s ta lle d an g le
P os it io ning P la tform o ve r s u bs e a we ll h ea ds
P ro d uc tio n R is er Ten s io ns a n d
B e nd in g M o m en ts
N o t F u n c t io na l
P ro du c tio n R is er S tro k e
N o t F u n c t io na l
A ir C a n pres s ures
N o t F u n c t io na l
A ir C a n Ris e r G uid e C o m pres s ion
N o t F u n c t io na l
In p ut to F a tig u e
D a m ag e P re dic t io n
M o d els
In p ut to F a tig u e
D a m ag e P re dic t io n
M o d els
S et R is er Ten s io n
N ot F un c tio n al
N/ A
M a n ag e ris e r te ns io n
fac to r
M o o rin g S y s te m
A d jus tm e n t in
A nt ic ipa tion o f w e a th er
or h ig h c u re n ts
M o o rin g S y s te m
A dju s tm e nt
M a na g e ris e r t en s io n
fac to r
id e nt fy p erform an c e
V e rify R is er R es p on s es a nd fat ig ue
prob le m s
m od e ls
ide nt ify e x c e s s ive ris e r
V e rify R is e r Q ua s i S ta tic
ex c urs ion s ; id e nt ify failure of
R es po n s e s
B C a ns t o s lip in g uide s
R is e r F at igu e
D a m ag e
N /A
W a rn o f A pp ro ac h to
S to p s
S et Ten s ion
M a in ta in Ten s ion a n d
Ide nt ify s o urc e s o f le a k s
E x p la in Te n s ion L o s s
N /A
N/ A
A s s e s s loa d s on B u oy a nc y
C an s
A s s e s s Lo ad E s tim at ion M o d els
N /A
inves tiga te t en d on failures
V a lid a te Ten do n Ten s io n E s tim at in g
M od e ls
in s u re t ha t C G is
w it hin prop er lim its ;
id e nt ify d e grad at io n
in te n do n an c ho rs
Tra c k m oo ring line
fa tigu e d am a ge ;
a n c h o r failures
N /A
Te n do n Te n s ion s
S et Ten s ion s
N/ A
N /A
M a in ta in Ten s ion a n d
W e igh t D is tribu tio n
M o orin g Lin e Ten s io ns a nd P a y ou t
S et Ten s ion s
P o s itio n in g over
s ub s e a w e llh ea d s
P os ition in g o ve r
s ub s ea w e llh e ad s
Te n s io n A d jus tm e n t for
h ig h c u rren ts a n d
H urric a ne s
Ide n tify c a us e s of M o oring
F a ilu re s an d q ua n tify tim e on -lin k fo r fat igu e e s t im a tio n
V e rify G lob a l M o tion M o d els
D ra ft
TL P - us e to verify
in s t alled t en d on t en s io ns
N/ A
N /A
B a lla s t /Trim / H ee l C o n tro l
es ta b lis h c au s e s o f e rrors in
ba lla s t c o nt ro l
R eq u ire d fo r c h ra c t eriz at io n of hu ll
B alla s t Tan k L evels
TL P - us e to verify
in s t alled t en d on t en s io ns
N/ A
N /A
B a lla s t Trim H ee l C o n tro l
S t ee l C at en ary R is er
In c lin at io n/ V ibrat io n
V erify S C R In s ta lle d
in c lina tion
N/ A
N /A
N/ A
es ta b lis h c au s e s o f e rrors in
ba lla s t c o nt ro l
h e lp to id e nt ify rea s on s fo r
c om p o ne n t filu re o r
d eg ra d at io n
R eq u ire d fo r c h ra c t eriz at io n of hu ll
verify F lo at er M o tio n in d uc e d
res p on s e in S CR
N /A
Tra c k in te g rit y of
c h a m be rs
Id e nt ify s in k a g e du e
to le a k s /c o llis io n
d am a g e
Tra c k Int ac t an d
D a m a ge d S ta bility
E s tim a te a nd Tra c k
S C R F a tigu e
3. Operational Decision Support
The primary function of an Integrated Marine Monitoring System is to provide real-time information in an
easy to understand format to the platform operators. The system provides “feedback” in a form and in a time frame that
permits the operators to evaluate the impact of their actions on important platform responses. Examples of the use of
real time data are:
• Production Riser Tension
Insure that the risers are properly tensioned
• Production Riser Stroke
Warn the operator of a situation where the riser stroke approaches the limits of the tensioning
system
• Buoyancy Can Chamber Pressure
In case loss of tension is observed, identify the leaking chamber (s)
• Platform Position, Mooring Line Tension and Payout
Positioning of the Spar over the subsea well heads
Warn of need for adjustment of tensions during high current events
• Platform Draft, Trim and Heel, and Ballast Tank Status
Guidance for weight and ballast control to maintain platform attitude. Certain drilling and riser
running operations are intolerant of excessive trim and heel of the platform
• Wind Velocity and Direction, Wave Height and Barometric Pressure
Guidance for helicopter, crane and boat operations
• Dynamic Tilt (Pitch and Roll)
Guidance for BOP handling operations
Guidance for heavy lifts with cranes
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Rio Oil & Gas Expo and Conference 2010
•
•
SCR Strains
FPS positioning for optimizing Touch Down Fatigue
Current Profiles
- Guidance for ROV operation or riser mating to the subsea well heads; Satisfaction of MMS
requirements for deepwater platforms
4. Forensic Engineering
Forensic engineering is the process of establishing the cause of accidents, equipment failures, storm damage,
lower than expected subsystem performance and identifying remedial action. Permanently recorded information about
the platform’s responses and the environmental parameters that influence them is essential in this process. Typical data
that are essential for Forensic Engineering are:
• Riser top tension and bending moment dynamic response
- Identification of the need for additional centralizers or the degradation of existing ones
• Mooring line tensions, payout and spar position
- Detect the occurrence of and cause of line failures and anchor “dragging”
- Assessment of cumulative fatigue damage to mooring components
• Platform position, surge, sway, pitch, roll and yaw
- Documentation of position to establish relationship to other facilities in case of platform drift off in a
hurricane
- Evaluate the effect of Vortex Induced Motions on Mooring and Riser Components
- Estimate fatigue damage accumulation in SCRs
• Platform inclination, draft and ballast levels
- Investigate accidents, mishaps due to incorrect loading, collisions with service vessel causing flooding
of voids
• Wind speed and direction and wave height
- Document the severity of intense storms which may interrupt operations or cause damage
• Air Gap (Estimated wave height and period)
- Document maximum water level excursion due to storms
- Assess damage due to “green water” impact on topsides
• SCR Top inclination and motion
- Track fatigue at SCR top and of flex joint
5. Integrity Monitoring
•
•
•
Maintain a continuous, real time picture shore side of the “health” of critical elements of the “marine
package” (Moorings and Tendons, intact and damaged stability, production riser fatigue life and export
riser fatigue life).
Evaluation of the impact of episodic events (Hurricanes and high current events, for example) on the
residual reliability of critical marine systems such as the mooring or tether system, production risers, export
risers, umbilicals, drilling equipment and critical elements of the hull and topsides structure.
Maintenance of estimates of the remaining life in fatigue sensitive structures.
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6. Overview of the IMMS
Figure 1 shows a schematic overview of a typical IMMS.
Figure 1. Schematic of Typical BMT IMMS
A typical IMMS may be comprised of the following measurement sub-systems:
Top Tensioned Riser Monitoring Sub-system
- Direct top tension and bending moment measurement
- Buoyancy Chamber and Stem Pressures
- Measurement of pressure in the tensioning rams
- Riser Stroke
• Platform Position Monitoring Sub-system
- Dual Redundant GPS Units with Combination UHF/Satellite antenna. Differential corrections are
acquired from the U.S. Coast Guard System. (performance degrades beyond 170–180 nautical miles
from stations)
- Globally Corrected GPS (Commercial Correction Service)
• Precision Static Inclination and Six Degree of Freedom Motion Measurement Sub-system consisting of:
- Three precision angular rate sensors
- Three precision linear accelerometers
• Ballast, Draft and Void Leakage
- Pressure sensors
- Bubbler Systems
- Air Gap Sensors
- Moisture Sensors
• Meteorological Monitoring
- Wind Speed and Direction (dual redundant anemometers)
- Air Temperature and Barometric Pressure
- Wave Height and Period
• Mooring Line Tension and Payout
- Usually supplied by Mooring Winch Vendor
•
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•
•
•
•
•
- Tension and payout data received by IMMS via Serial Link to Winch PLC’s
Current Profiles
- Surface to keel
- Deep Profile (from Platform)
- Lower Profile (Bottom up)
Steel Catenary Riser Flex Joint Relative Inclination (Static and Dynamic)
- Subsea Static and Dynamic Inclination Measurement Units below flex joints
- Same above the flex joint or inclination of the platform
Steel Catenary Riser Bending and Tension (Static and Dynamic)
- Subsea Strain Measurement Units below flex joints
The IMMS Data Concentrator/Server
- PC based
- Networked with other Platform Control and Monitoring Systems
- Remote Access
- Non volatile data storage
Client Data Center
- Data Management, Quality Assurance and Distribution
7. Description of Important Measurement Subsystems
7.1 Wave Estimation – Air Gap Measurement Subsystem
The ideal way to measure the wave environment that impinges on a platform is with a wave buoy. It can be
placed far enough away to avoid contamination due to the waves reflected and generated by the platform. However, a
wave buoy is not a suitable, low maintenance, accessible device for a long lived installation. Instead we have chosen to
use a non contact, platform mounted device that measures the instantaneous distance between a suitable place on the
platform and the sea surface. That distance is measured by low powered microwave radar ranging device(s). For semi
submersibles and TLPs, the air gap sensors are generally located mid way between columns to minimize interference.
For Spars, the air gap sensors are located as far outboard of the hull as is possible on the corners of the Cellar Deck.
Three or four are recommended to facilitate corrections for reflected/and refracted waves. The time record is processed
by the IMMS to correct for platform motion and to provide an estimate of the significant height and peak period of the
waves. Notwithstanding the reflections from the platform, the wave height estimated by these sensors and uncorrected
for reflections/refractions was found to agree quite well with a nearby NOAA Wave Buoy in hurricane conditions. A
typical installation is shown in Figure 2.
Figure 2. Microwave Radar Air Gap Sensor
7.2 Wind Speed and Direction
The measurement of wind speed and direction is very important for providing advice to helicopters and
approaching service vessels and for quantifying the environmental forces on the platforms and on derricks and flare
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towers. Crane operations are susceptible to high winds and wind speed is used as a criterion for permitting crane
operations. It is difficult to get uncontaminated estimates of wind speed and direction on a production platform because
of the turbulence caused by flow over the bluff shapes of the platform.
Furthermore, on production platforms, some structures that appear to be ideal platforms for a wind sensor, like
drilling derricks, are more often than not temporary or mobile. Flare towers, another apparently ideal location, can be
hazardous to the wind sensor during large volume flaring events. Therefore, we prefer to locate wind sensors on the tops
of the crane A-Frames and deal with the added complication of using the crane slip rings to provide data and power
transmission and measuring the heading of the crane so the wind direction estimates are always valid. Figure 3
illustrates a typical anemometer installation on an offshore platform. Standard RM Young anemometers are employed.
A crane azimuth sensor, shown in Figure 4, was developed to provide correction data for the anemometer. It consists of
an angular encoder mechanically linking the slip ring assembly to the crane. It provides 1 degree accuracy crane
heading (relative to platform North) to the IMMS. This is not suitable for a platform that may be expected to have
significant yaw.
Figure 3. Anemometer installed on crane top
Figure 4. BMT Electro Mechanical Angular Encoder Retrofit to Crane Sliprings
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7.3 Current Monitoring
Three types of current monitoring will be discussed:
• Current Profiles between the Surface and the bottom of the platform
• Deep current profiles (below the Keel)
• Deep Current Profiles from the sea floor up
These options are shown schematically in Figure 5 for a semi-submersible.
UPPER. ADCP
30m below MSL
SEA
SURFACE
Long range horizontal
ADCP
UPPER. First bin:
72m below MSL
UPPER. 33 measurement
bins of 32m length
Water
Depth
approx.
1900m
MID-DEPTH. Depth of last
valid bin: 924m ASB / 976m
below MSL
UPPER. Depth of last valid bin:1096m
below MSL/ 804m ASB
MID-DEPTH. 28 measurement
bins of 16m length
Riser Mounted ADCP
ADCP 468m ASB
MID-DEPTH. First bin:
492m ASB
SEABED. Last valid bin:
476m ASB
SEABED. 28 measurement
bins of 16m length
LMRP Mounted ADCP
ADCP 20m ASB
SEABED. First
bin: 44m ASB
BOP &
LMRP
Figure 5. Example of possible options for Current Monitoring on a Semi-Submersible
Surface to Platform Keel
For Spars, it is very difficult to obtain an uncontaminated profile from the water surface to the bottom of the
hard tank (–250 feet MSL). The flow field around the spar hull is disturbed significantly by its presence. Multiple
Horizontal ADCPs that are intended to provide the current speed and direction in a river by “looking” out across the
flow have been employed on numerous platforms. The range of these instruments is on the order of 200 meters. Current
vectors in the plane of the device are relatively uncontaminated at or near the instrument’s extreme range. In some
cases, the H-ADCPs have been installed on the hull within diver range of the surface or can be bundled with the
downward looking profilers as is illustrated in Figure 6. In some cases, H-ADCPs have been installed with a small tilt
to provide a profile that spans the hard tank with the full understanding that the observations from the bins close to the
sensor may be contaminated by the wake of the hull. Such an installation is shown in Figure 7. For Truss Spars, the
estimate of the current vectors from the hard tank to the bottom of the truss (soft tank) is less contaminated due to the
sparse spacing of structural members. For TLPs and Semi Submersibles, the task of producing valid current
measurements over the depth of the hull is much less difficult since the base line of the hulls are relatively shallow (50–
100 feet).
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Figure 6. Combination 38 kHz ADCP Deep Profiler and 300 kHz horizontal ADCP installation on West Africa FPSO
Figure 7. Upward tilted 300 kHz H-ADCP mounted on Heave Plate at approximately 300 feet below the free surface of
BP’s Mad Dog spar
Platform Mounted Deep Profiles
The 38 kHz ADCP from RD Instruments is the sensor that provides the deepest penetration available today in
a single instrument and is recommended for installation on new platforms in deep water. The range of the instrument is
nominally 1000 meters.
The actual vertical penetration depends upon the inclination that may be required to prevent impingement of
the beams on either the hull, production risers, mooring lines, steel catenary risers or umbilicals, etc. Figure 8 shows the
final result of a beam pattern interference analysis for a typical installation on a Truss Spar. The resulting tilt of the
sensor is 37 degrees and the actual vertical penetration below the sensor is 700 meters. Figure 9 is a photograph of a
typical deployment fixture for a 38 kHz ADCP. Another alternative is to deploy a 75 KHz ADCP looking downward
from a heave plate or pontoon.
Figure 8. Example of Beam Pattern Interference Analysis for 38 kHz ADCP installation
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Shipshape FPS Mounted Surface Current Monitoring Systems
Horizontal ADCP’s can be used to estimate surface current in the vicinity of shipshape FPSO’s but because of
the interference provided by a ship shape hull, several are required on typically only one will be offering useful results
depending upon the direction of the current.
Figure 9. ROV Deployable HADCP on Greater Plutonio FPSO Outward Looking (Hybrid Riser Tower Acoustic
Positioning System shared the Fixture with the HADCP)
Bottom Current Profiles
A permanent bottom founded current meter has been deployed on some of the platforms. It is shown in Figure
10. It is a battery powered 75 KHz ADCP. It is mounted on a robust tripod that also contains and acoustic modem. The
tripod is aligned by the ROV to “aim” the acoustic modem at one of the spare pull tubes into which a pig containing an
acoustic modem has been lowered. This package has been combined with a platform mounted 75 KHz Downward
looking ADCP on a heave plate and an H-ADCP—tilted slightly upward on the same heave plate (see Figure 7).
Together these three packages provide full water depth coverage in the 4000 feet water depth as may be seen on an
IMMS composite current screen (See Figure 11).
Figure 10. Bottom Mounted 75 kHz ADCP with Acoustic Modem in approximately 4500 Feet of Water near BP’s Mad
Dog spar
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Figure 11. Typical screen plot of Combined Current Profile
7.3 Riser Top Tension Measurement Sub System (Buoyancy Can Supported Risers)
On most Spars, each riser is supported by air or nitrogen-filled buoyancy cans, which communicate with the
sea. Each of these multi-chamber buoyancy cans is integral to a stem through which the riser passes. The stem extends
from just below the surface tree to the keel and is also a buoyancy chamber. The stem terminates at its top with the stem
adapter. The stem adapter has been fitted to transmit the buoyancy load through three load cells into the riser top
connector, providing a direct measurement of riser tension and bending moment. The arrangement is shown in a
photograph in Figure 12.
Figure 12. Load Cell Arrangement in TTRMS
The Top Tensioned Riser Monitoring System (TTRMS) consists of three strain gage compression load cells for
each riser. The load cells individually exhibit 0.25% of full scale measurement range accuracy. The style of load cell
chosen for this service have been demonstrated to have less than 0.25% long term zero drift over an 8 year period. This
is an important consideration because spurious drift of the load cell might be interpreted as a gradual change in
buoyancy. For one riser set, the assembly of three load cells together was exposed to known riser loads up to 1500 kips.
The resulting composite accuracy in the tension range of interest (600–1500 Kips) was 1% or better. The load cell strain
signal is transmitted to an explosion proof enclosure installed on each riser’s work platform. In this enclosure, three
strain gage interface modules are located along with three intrinsic safety barriers and three IS rated relays to provide
for remote actuation of a zero simulation and a shunt calibration. Power to the modules and RS-485 signals are
transmitted to the control room via two twisted pairs in the umbilical that connects the well head work platform to the
spar hull.
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Bending Moment Measurement
Bending moments at the top of the riser are estimated from the differences between the load cell readings and
the spacing between the load cells. The bending moment calculations are made in the IMMS software in real time.
Frequency Response of the Riser Tension and Bending Moment Measurements
The primary function of the TTRMS is to monitor riser tension to permit setting the tension to the desired
level, and to detect leakage in the buoyancy support system. These objectives can be achieved with a very low
frequency response system. However, by increasing the frequency response and also maintaining a high resolution, it is
possible to detect the occurrence and approximate intensity of lateral vibration of the riser (VIV). This approach was
implemented on a spar and has been shown to function as expected during high current events.
Riser Stroke Measurement System
This measurement is the vertical displacement of a riser relative to the spar hull. It serves two primary
purposes. First, it provides operating personnel with a measure of riser position relative to the hull during operations
where the platform is intentionally offset for work over. The measurement provides a remote indication of the distance
from the upper and lower riser stops from the limit stops.
Second, in conjunction with the vessel draft, measurement of the “stroke” permits establishment of the distance
from the Mean Water Surface to the buoyancy chamber tops thereby providing, in conjunction with the head
measurement in each buoyancy chamber, the true estimate of the air volume in each chamber. This is essential to
provide a redundant estimate of total buoyant force acting on the riser.
7.4 Platform Attitude and 6 Degrees of Freedom Motions
Platform trim, heel, roll, pitch and three accelerations are measured using a six-degree of freedom motion
package that is preferably located as close to the lateral center of gravity as is possible and on a substantial structural
member that will not be expected to vibrate. The package consists of three each high precision angular rate sensors and
linear accelerometers. The package also contains local signal conditioning and digitizing equipment. The analog data is
filtered with high quality analog anti-alias filters. Digitization is performed with a 16 bit A to D converter. The raw
outputs of the accelerometers and rate sensors are stored for later post processing. While there are commercial off the
shelf packages for 6 DOF measurements including true heading, none provide direct access to the “raw” data from the
precision rate sensors and accelerometers. Only the estimation of the static heel and trim and the dynamic pitch and roll
is performed in real time, since it is only these parameters that are of interest to the operators. Post processing is
performed on the records monthly and for special events to provide data about the platform hull angular response and
linear displacements at critical locations on the platform (riser keel joint, SCR porches, compliant riser guides, drill
floor etc.).
7.5 Static Inclination
The most accurate and robust method for measurement of static or mean inclination of a platform is the use of
linear accelerometers. The output of a linear accelerometer statically tilted θ degrees in the earth's gravity field is g•sin
θ. The long-term average of the accelerometer is used to estimate the inclination in the gravity field. The expected range
of inclination of the spar is ± 5 degrees under the most extreme conditions. Normal day-to-day variations in tilt for a
spar are less than 1 degree. To detect inclinations of this order accurately, a self-contained inclinometer based upon
biaxial quartz flexure, temperature corrected linear accelerometers is used. The output of two biaxial accelerometers
(one aligned with platform North (+) and one aligned with Platform West (+) is filtered in real time with 15 minute
running average. This averages out the variation in acceleration due to surge, sway, pitch and roll occurring at wave
periods (5 to 20 seconds), natural pitch and roll periods (50 to 60 seconds) and Hull VIV (200 seconds). The arc sine of
the averaged acceleration produces an accurate but delayed estimate of static inclination.
7.6 Steel Catenary Riser Monitoring
Static and Dynamic Inclination
The comprehensive monitoring of the response of a steel catenary riser is an expensive undertaking. However,
useful information can be gained from the measurement of the static and dynamic, relative, angular motion across the
flex joint. This can be accomplished with measurement packages that with ROV service, can last the life of the
platform. For one Spar and one Semi Submersible in the Gulf of Mexico and for one West Africa FPSO, a system has
been deployed that measures the earth fixed static and dynamic inclination below the flex joint of the export riser. That
system uses the hull inclination to estimate the relative inclination across the flex joint.
This package is ROV retrievable and deployable. It is shown in Figure 13 and Figure 14. It is hard wired to the
IMMS via an ROV mateable connector and molded Subsea cable. For situations where the inclinometer package is
distant from the IMMS central computer, the processing electronics are included in the subsea package as in Figure 14.
In situations where the SCR’s Flex Joint is close to the weather deck of a Semi or shipshape FPSO, it is convenient to
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eliminate the subsea electronics thereby increasing the MTBF of the submerged equipment and locating the processor
on a weather deck for easy access and maintenance. This also makes the subsea package easier to service with a diver or
ROV. Figure 15 shows a typical compact subsea package of the type deployed on Total’s AKPO SCVR’s and OOLs
(Le-Douaron et al 2009).
The system has been designed and carefully calibrated to achieve accuracy in the estimation of static and
dynamic inclination of better than 0.01 degrees. To validate the performance of the package prior to deployment, it was
subjected to a test wherein actual Spar inclination records were used to drive a platform on which the package was
mounted. Figure 16 is an example of the test record. It can be seen that the inclinometer output tracks the imposed
motion quite well. The maximum dispersion of the measured versus the imposed inclination is less than 0.01 degrees.
The unit has been successfully deployed on the SCR and is producing data with extremely high accuracy and
sensitivity.
There are now eight of these packages in subsea service, operating essentially trouble-free for between 1 and 4
years.
BMT Subsea
Inclinometer-in
service 4 years fault
free at -500 feet
Figure 13. BMT High Precision Static and Dynamic Subsea Inclinometer in ROV Receptacle on Holstein Spar SCR
Figure 14. BMT High Precision Static and Dynamic Subsea Inclinometer (4 Degree of Freedom Inertial Package)
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Figure 15. 4-Degree of Freedom Inertial Package for use in close proximity to Surface Processor
Figure 16. Comparison of Imposed and Measured Inclination (actual spar inclination record used for test)
SCR/OOL Top Strain Monitoring
BMT has deployed two SCR Strain Monitoring Systems to date. One is located on the Gulf of Mexico Spar
and the other is on the SCRs on Total’s AKPO FPSO (Le-Douaron et al 2009). The strain stations consist of four
LVDT type sensors encapsulated in pressure balanced, oil filled enclosures and located at 90 degree intervals around
the circumference of the pipe. The sensors are anchored at either end to custom designed, steel pipe clamps. The
insulation was removed in the vicinity of each top strain station location leaving only the anti corrosion coating.
Extensive tests had been conducted by BMT to demonstrate that it was possible to measure tensile strain accurately by
clamping the sensors to the anti-corrosion coating rather than having to remove this important anti-corrosion layer to
bare steel. The SCR strain stations are designed to provide a 20 year service life without maintenance. Hence, these
strain sensors are encased in a pressure compensated bellows and interconnected with pressure balanced oil filled
(PBOF) hose cabling system and diver mate-able connectors on each sensor and ROV mate-able connection to the
strain station. Figure 17 shows as-installed configuration of an SCR Top Strain Station without the protective cover.
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Figure 17. SCR Top Strain Station
The SCR top strain stations are connected with diver serviceable cables to three respective FPSO deck
mounted DAQ units. The FPSO DAQ units digitize the analog data from the sensors stations and transmit continuously,
sampled strain station to the RMS instrumentation rack located in the control room. The deck DAQs are synchronized
amongst themselves by a trigger signal originating at the RMS. Figure 18 shows BMT’s Strain Sensor Assembly
mounted on an SCR prior to installation offshore.
Figure 18. Subsea Strain Sensing Assembly before deployment on a Spar SCR
7.7 Tendon Tension Measurement
Tendon tension measurements are essential for the real-time operation of a TLP to (a) maintain a continuous
assessment of the integrity of the tendons and (b) to maintain control over the weight distribution of TLPs such that the
TLP will be prepared to endure any reasonable combination of extreme environmental conditions without the tendons
experiencing zero tension or compression or exceeding the maximum allowable tension.
In Table 1, four SeaStar® Tension Leg Platforms are listed. These platforms were designed and fabricated by
Atlantia Offshore Ltd. (now part of the IHC Caland Group). Each platform is fitted with a “porch” based tendon
tension measurement system. The system is simple in principal. Each tendon is supported on its porch by three
underwater compression load cells. Figure 19 is a photograph that shows the typical installation of a compression load
cell. The load cells are supported by a heavy support ring that is embedded in the porch and which has machined
recesses for the load cells. The load cells are equipped with double water barriers and there are two independent strain
gage bridges for redundancy. Each of the strain circuits has a separate underwater connector and armored Subsea cable
to the Signal Processing Modules in the top of the central column of the SeaStar®. The processing systems are dual
redundant as well. The porch based systems permit the complete installation of the tendon tension measurement system
while the TLP is in the fabrication yard. The system integrity can be checked in a flooded drydock prior to deployment.
Upon arrival at the installation site, the system has a valid zero and begins to offer tension and bending data, from the
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moment the tendons apply load to the flex joint. Consequently, the system is used to control the adjustment of the
tendon adjustment “nut” during installation. A typical display of tendon tension information is shown in Figure 20.
Figure 19. Typical Tendon Tension Measurement System load cell installation
Figure 20. Typical Tendon Tension System Display
7.8 Data Acquisition, Archiving and Network Interfaces
The IMMS computer processes the data from the various measurement sub-systems. It has the following
functionality:
• Acquire all sensor data synchronized in time stamped files
• Identify and alarm malfunctioning sensors and other components in the IMMS
• Provide “user friendly” and timely displays of operationally important information
• Archive the measured data on a common time base
• Automatically prepare daily reports and e-mail to personnel who are cognizant on and off the platform
• Provide requested data to other process control networks on the platform
• Provide real time access to the IMMS from shore side work stations via an Internet Connection
A typical IMMS collects raw data from 100 to 200 “points”. In real-time, the IMMS also calculates additional
virtual channels of data. Only raw data, collected at from 2 to 10 samples per second is stored. Each file may be of 30
minutes to several hours duration and consists of the raw data, the calibration constants, the constants used in the
derivation of the virtual channels and a statistics file. The data is stored on the hard disc in a looped buffer and is
downloaded, without interrupting the data acquisition process, to a magneto optical drive. The hard disc can contain up
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to 12 months data before overwriting, thereby insuring that the MO discs are received on shore, duplicated, distributed
and inspected before the data on the hard drive is destroyed. On some platforms, work is progressing to move the raw
data files to the shore over high bandwidth links removing the step of handling the Magneto Optical discs.
7.9 Graphical User Interfaces
The IMMS data acquisition module processes and exchanges system data that allow display screens to provide
meaningful information to the operator and allow operator interaction.
There are between 15 and 20 different input and display screens that can be viewed by operators of the IMMS.
A sample set is listed below:
• Main Menu Display
• Global Overview Display
• Riser Summary Display
• Riser Detail Display
• Ballast and Leak Detect Display
• Metocean Display
• Helicopter Landing Display
• Current Profile Display
- Downward Looking, Spar Mounted 38 kHz ADCP Current History Display
- Upward Looking, Bottom Mounted 75 kHz ADCP Current History Display
- Horizontal Spar Mounted 300 kHz H-ADCP Current History Display
• Mooring Status/Alarm Screen
• IMMS Configuration Display
• Data Analysis Menu Display
- Time Series Display
- Historical Trend Display
- Archive Data Display
• Status/Event Display/Log
• Mean AD Display
Main Menu Display
The Main Menu Display is a simple tool for navigation among all of the available Graphical User Interfaces in
a BMT IMMS. A typical display is shown in Figure 21. The operator simply selects the icon (not an active screen) that
represents the GUI that he wishes to examine and that live display appears. In Figure 21, one can select 11 GUI’s. The
data analysis icon actually has four subscreens that permit the operator to manipulate time histories, trend plots of
statistical parameters, perform spectral analysis and create a statistical summary for any period that has been stored on
the system hard drive. The data is typically resident on the hard drive for 1 year or more.
Figure 21. Typical Main Menu Display
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Global Overview Display
The Global Overview Display is custom built for the particular type of installation and is shown in Figure 22.
The display summarizes in one GUI the vital information about a moored FPS. It emphasizes the lateral offset and line
tensions as well as the environmental forces acting on the platform. In Figure 22, additional important information is
displayed about the associated Hybrid Riser Tower including tension, bending moments, inclination etc. With this GUI
the operator may observe at a glance most of the important aspects of the entire floating system.
Figure 22. Global Overview Display for an FPSO and Hybrid Riser Tower (Zimmermann et al 2008[6])
Helideck Display
BMT IMMS’s now include a Helideck Monitoring graphical user interface that is compliant with CAP 437
This is shown in Figure 23. The display provides a picture of Metocean parameters and Helideck motion characteristics
that assist in assessing the feasibility of landing a helicopter on the platform.
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Figure 23. Helideck Display (CAP 437 Compliant)
Riser Detail Screen
Figure 24 illustrates an important graphical user interface for Spars. Many spars employ buoyancy cans in the
well bay to provide the required uplift for the production risers. BMT provides the top tension monitoring system for
these types of risers. The particular one shown is for the Horn Mountain Spar (R.Y Edwards et al 2003 [7]). That
system employed two redundant methods to monitor the integrity of the riser tensioning system. The buoyancy can
compartment pressure and the directly measured load applied to the riser are displayed along with the riser stroke
thereby providing a single snapshot of riser health.
Figure 24. Buoyancy Can Supported (Spar) Riser Screen
Daily Reports
On some platforms, every day at the time of the shift change, the previous day’s data is processed into a
succinct tabular and graphical report. The report focuses on the wind, waves, current, trim and heel, pitch and roll,
mooring tensions and riser tensions. It is e-mailed to the Offshore Installation Manager, Barge Engineer and numerous
other persons who are cognizant both offshore and onshore. This reporting system is in-place now only on few
platforms.
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Monthly Reports
For a number of the platforms listed in Table 1, at the end of every month, that month’s data is post processed
on shore. An abbreviated report that deals with the same parameters as those in the daily report accompanied by a letter
discussing the data is e-mailed to the same recipients as for the daily report. This report is in the form of a month long
time series of the 30 minute statistics (maximum, minimum, mean and rms) for all parameters of interest. Inspection of
this record permits (a) identification of noteworthy events that should be analyzed more closely (b) identification of
malfunctioning sensors that must be repaired or serviced.
Remote Access to the IMMS
On all of the platforms cited, designated personnel on the platform (OIM, Barge Engineer, Driller, Marine
Supervisor etc.) are provided with a piece of software that permits them to view the Graphical User Interfaces and
control the IMMS from any PC or work station that has access to the same network to which the IMMS is connected.
This permits the information to be shared without a physical presence in the control or equipment room where the
IMMS Server is located. Some of the owners of these platforms have gone the next step to have access, in real time to
the displays and the data from the IMMS at shore side offices.
8. Client Data Center – Onshore Integrity Data Management
Long-term IMMS data handling and detailed analyses are usually performed onshore. IMMS data collected
offshore can be streamed virtually in real time via a dedicated fiber optic or a satellite communication line directly from
an offshore platform to the BMT Client Data Center (CDC). The core of the CDC is a dedicated CDC Data server that
is carefully configured for each BMT client. It represents a safe and secure physical and networking system for data
management, sharing, post-processing, and visualization of the key platform integrity parameters. CDC Data resolves
bottlenecks related to labor intensive and time consuming shipping and archiving of measured data that is traditionally
backed-up offshore on MO disks, DVDs, or memory sticks and then physically stored in the client’s office. Replacing
manual data handling with the automated CDC Data service increases accessibility to the data, reduces long-term costs,
and eliminates loss of data in the mail or due to inappropriate handling of the backup media.
Access to the IMMS data on the CDC Data is Internet-based, so the data can be securely shared with multiple
authorized users twenty-four hours a day, seven days a week. Figure 25 shows the data flow from the IMMS offshore to
through the CDC to the users.
Figure 25. Client Data Center concept
Once the IMMS data is transferred to the CDC, the measured data are further post-processed automatically in a
batch mode and the results become available instantly for inspection. BMT also provides interpretation of the results by
knowledgeable data analysts and further by offshore engineer specialists. The IMMS data interpretations are
summarized and presented to the client, along with cautionary advice and recommendations about the integrity of the
system for the continued safe operation of the facility. The available IMMS data on the CDC are not only important in
real time, but the CDC system also provides access to the historical trends. A lack of the access to such long-term trends
can affect utilization, safety, and the economy of the platform over its lifetime. Data from more than 20 platforms listed
in Tables 1, 2 and 3 streams into BMT Client Data Centers every day.
22
Rio Oil & Gas Expo and Conference 2010
9. Contributions of Real Data to Platform Performance, Integrity and Forensic Analysis
Data acquired and archived by the IMMSs on offshore platforms in the Gulf of Mexico have contributed to
improving performance, understanding platform integrity and characterizing the marine environment.
9.1 The Usefulness of Air Gap Sensors for Wave Estimation
Air gap sensors are good estimators of wave height on platforms that are relatively transparent to waves such
as semi submersibles and TLPs. On Spars and other bluff shapes there is a valid concern that the air gap data will be a
poor estimator of the undisturbed height of waves impinging on the platform (Prislin I. and Blom, A.K. 2004[5]).
Using data from a spar, comparisons between significant wave heights measured with an air gap sensor
mounted on the platform and those reported by the nearby NDBC weather buoy station shows reasonable agreement for
wave heights in excess of 7 feet (Figure 26). For the data shown, the NDBC station is located a few miles from a
platform. The measured waves at the platform are result of direct measurement of wave elevation by an air-gap sensor.
Corrections are made for the small motions of the Spar but no attempt was made to correct for waves reflected by the
platform. The NDBC wave data are result of an indirect measurements, derived from the heave acceleration motions of
the buoy.
16
14
Significant Wave Height Hs (ft)
Hs (AirGap Sensor)
12
Hs (NDBC 42041)
10
8
6
4
2
31-Oct
25-Oct
19-Oct
13-Oct
7-Oct
1-Oct
0
Figure 26. Buoyancy Can Supported (Spar) Riser Screen
10. Summary and Conclusions
Integrated Marine Monitoring Systems are state-of-the-art computer based monitoring systems that have been
successfully integrated into platform management structures on an increasing number of Deep Water Offshore
Platforms worldwide.
10.1 Operational Tool
IMMSs have provided real contributions to efficient tensioning of production risers, TLP tendons and mooring
installations. The systems are most effective when Platform Operators are invited to participate in the development of
the functional objectives of the IMMS designs and especially in the configuration of the Graphical User Interfaces.
10.2 Forensic and Engineering Analysis
The IMMSs for the platforms in Table have provided remarkable data for some of the major storms to pass
through the Gulf of Mexico in the last few years among them Hannah, Isidore, Lili and Ivan. The IMMS data has been
demonstrated to provide guidance for the improvement of important subsystems on Deep Water Platforms.
11. Acknowledgements
The authors are grateful to the owners of the platforms listed in Tables 1&2 (BP Exploration & Production
Inc., ChevronTexaco EPTC, Dominion Exploration & Production Inc., ENI Petroleum, ExxonMobil, Anadarko,
Murphy Exploration & Production Company, Petrobras, Shell, Total Exploration & Production, Williams Energy
Services, Unocal E&P, Shell Oil Company, BHP Billiton) and to their contractors (ABB Lummus Global, Inc., KBR,
23
Rio Oil & Gas Expo and Conference 2010
ACERGY, Saipem, SBM Atlantia Offshore, Inc., Technip Offshore Inc. and J.R. McDermott Inc.) for the opportunity
to be involved in the development, installation, commissioning and continuing data quality assurance for them.
Moreover, none of these installations would have been successful without the enthusiastic participation of the platform
operating personnel. It is gratifying to BMT technical personnel to see the monitoring technology embraced by the day
to day users and to see the systems increase in number as well as being improved and made more relevant by their
input.
12. References
[1]PETERS, D. J. H., ZIMMER, R. A., HEIN, N. W. Jr., WANG, W. J., LEVERETTE, S. J., BOZEMAN, J.D. Weight
control, performance monitoring and in-situ inspection of the TLWP. Offshore Technology Conference, Houston,
Texas, USA, Paper 6363, 1990a.
[2]DENISON, E. B., ROTHEBERG, R. H., MERCIER, R. S., FORRISTALL, G. Z., VAN LEGGLELO, B.
Performance monitoring instrumentation system for Auger Tension Leg Platform, 1990b.
[3]EDWARDS, R. Y., PRISLIN, I., JOHNSON, T. L., CAMPMAN, C. R., LEVERETTE, S. J., HALKYARD, J.
Review of 17 real-time, environment, response, and integrity monitoring systems on Floating Production platforms
in the deep waters of the Gulf of Mexico. Offshore Technology Conference, Houston, Texas, USA, Paper 17650,
2005.
[4]LE DOUARON, S., VUATTIER, S., PERROMAT, V., ABBASI, T. A., HENNESSY, W. F., PRISLIN, I.,
EDWARDS, R. Y., RICBOURG, C.
Akpo Riser Integrity Monitoring System Design, Deployment,
Commissioning and Start-Up, Deep Offshore Technology Conference, Monte Carlo, Monaco, 2009.
[5]PRISLIN, I., BLOM, A. K. Significance of short crested and diffracted waves on full scale motion correlation of a
truss spar. Civil Engineering in the Oceans VI (CE06), ASCE, Baltimore, MD, USA, Paper 40775-6325, 2004.
[6]ZIMMERMAN, C., TALMONT, P., EDWARDS, R. Y., DULEY, D. W., DE LA CRUZ, D., MAROJU, S. S.
Recent experience with a comprehensive riser tower monitoring system. Deep Offshore Technology Conference,
New Orleans, Louisiana, USA, 2009.
[7]EDWARDS, R. Y., SHILLING, R., THETHI, R., KARAKAYA, M. BP Horn Mountain SPAR - results of
comprehensive monitoring of platform and riser responses. Deep Offshore Technology Conference, Marseille,
France, 2003.
[8]PRISLIN, I. Client Data Center for Integrity Management of Offshore Platforms. Sea Technology, May 2010.
24
Independent Remote Monitoring
A new black box solution for remote monitoring and
communication with offshore drilling rigs and production
platforms via web based graphical user interface.
The ability to monitor environmental conditions and
the dynamic performance of deepwater facilities
during extreme offshore conditions is becoming
increasingly important. BMT’s Independent Remote Monitoring System (IRMS) allows operators
to maintain communications with the asset during
abandonment and receive key environmental and
performance data in real-time along with video
and still image capture of actual conditions on the
facility. The IRMS automatically transmits high quality environmental and dynamic performance data
to provide stakeholders and technical experts with
operational decision making tools and to assist
with risk analysis following re-boarding operations.
Key IRMS Features:
• Fully Independent system, does not require any integration with platform/vessel power and communications
infrastructure;
• Web based access to near real-time offshore data and
imagery;
• Fully configurable to custom specifications: standard sensors include monitoring of pitch, roll, surge,
sway, heave, yaw, position, wind speed, wind direction
barometric pressure, temperature, humidity and battery
condition;
• Environmental and platform response data stored
on both offshore IRMS computer and dedicated web
server;
• Color Imagery frequently transmitted to shore in still
image, video formats and high frequency records
from offshore cameras stored ready for download post
evacuation;
• Operational in extreme storm
conditions;
• Remote communications with
shore base using integrated satellite transmission system;
•
Near real-time data collected during
extreme events transmitted to shore
for instant evaluation;
•
Data summary and trending
plots automatically generated
and displayed on user interface
screens;
•
Independent power supply from
internal batteries and solar charging system;
•
Ability to communicate with and
control IRMS from shore via web
based graphical user interface;
•
Satellite positioning systems to
track offset and to locate loose rigs
during and after a storm;
•
Easily mounted instrument subframe using bolted deck plate
assembly, no offshore welding
required for installation of any
system components—allows
system portability and option of
re-deployment;
•
Compact deck footprint of 60” x
24” (1524mm x 610mm) includes
main module and full instrument
array;
•
Units operational from June 2006
on Gulf of Mexico deepwater
facilities.
www.scimar.com
[email protected]
IRMS System Specifications:
The IRMS is a robust, stand-alone instrument array designed to perform in extreme offshore conditions. The system is housed in an aluminum frame and integral skid coupled
to deck mounted steel foundation beams.
1. Ultrasonic wind sensor – resolution 1 deg, accuracy ± 2 deg with wind speed over
1m/s. Records up to 156 knots (80 m/s)
2. Differential GPS providing sub-meter accuracy in real time using Satellite Based Augmentation Systems (e.g. WAAS)
3. Combined pressure, humidity and temperature transmitter. Pressure range 50 to 1100hPa, accuracy ± 0.2 hPa. Humidity ± 1% RH with 100% RH humidity range. Temperature measurement range -36ºC to + 60ºC (-33 to +140ºF with accuracy at + 20ºC ± 0.2ºC (0.4 ºF)
4. Stabilized satellite antenna linked to geostationary satellite service with global coverage
5. 2 x 125W high efficiency solar panels using silicon nitride multi crystalline sili
con-coated cells, 2 x 17.3V charging capacity at maximum power
6. Fiberglass electronics enclosures fully compliant with NEMA 4X, IP56, UL listed
7. High performance gel batteries provide operation up to 6 days without solar re-
charging, deep cycle, maintenance-free batteries with 200 Ah capacity
8. Deck mounting arrangement using W6 x 15 foundation beams
9. 6 degree of freedom package consisting of 3 accelerometers and 3 angular rate sensors. Static and dynamic roll/pitch accuracy 0.01º standard error. Acceleration
accuracy 0.001 m/s2 RMS
10.Permanently connected integrated emergency satellite telephone
11.Low power computer, LCD screen, keyboard and trackball mouse accessible within enclosure USB connections to download to various storage media
12.Battery charge controller and optional AC power charging facility
13.Digital camera system with video sample rate up to 4Hz and 640 x 480 imagery. System supports up to four cameras in the array, EX-rated housing available for Class 1, Div 1 areas
BMT Scientific Marine Services
9835 Whithorn Drive
Houston, TX 77095
Ph: 281.858.8090
Fx: 281.858.8898
BMT Scientific Marine Services
955 Borra Place, Suite 100
Escondido, CA 92029
Ph: 760.737.3505
Fx: 760.737.0232
Integrated Marine Monitoring System
Performance monitoring helps reduce risk in the offshore
environment by keeping operators informed about the
state of the environment and the platform in real time.
With platform safety in mind, operational risk reduction
and operating cost savings are the key benefits for
commissioning a monitoring system.
Measurement Options:
• Response;
• Tendon Tension;
• Riser Tension and Stroke;
• Platform Ballast Control, Stability
and Loading;
• Wind Speed and Direction;
• Mooring Line Load and Payout;
• GPS Precise Position Monitoring;
• Environment
• Air Temperature, Pressure and Humidity;
• Wave Height/Air Gap;
• Current Profiles.
BMT Scientific Marine Services has
proven experience implementing a
number of successful and innovative platform monitoring systems on
Semi-Submersibles, Spars, TLPs, and
mini-TLPs. We can customize an integrated system to meet your specific
needs.
Combining the latest technology with
our offshore experience, our customized monitoring systems are practical,
user friendly and economical.
Features:
• Acquire all sensor data synchronized in time stamped files;
• Identify and alarm malfunctioning
sensors and other components;
• Display the data in a form and time
frame appropriate to the operational requirements;
• Provide “user friendly” displays of
operationally important information;
• Reliably archives the measured
data;
• Data access from multiple platform
locations as well as shore-based
computers via networks or other
data links;
• Interfaces to available platform
control systems;
• Capacity to perform calibrations
on load sensors (tendon, riser,
and/or mooring tensions).
Operational displays.
www.scimar.com
[email protected]
BMT Scientific Marine Services
9835 Whithorn Drive
Houston, TX 77095
Ph: 281.858.8090
Fx: 281.858.8898
BMT Scientific Marine Services
955 Borra Place, Suite 100
Escondido, CA 92029
Ph: 760.737.3505
Fx: 760.737.0232
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