Integrated Marine Monitoring System - BMT Group

IBP3407_10 

REVIEW OF FLOATING PRODUCTION PLATFORM REAL-TIME 

INTEGRITY MONITORING SYSTEMS WORLDWIDE 

Craig Campman 1 , Roderick Edwards 2 , William “Bud” Hennessy 3 

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, 13- 

16, 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

1. Introduction 

Rio Oil & Gas Expo and Conference 2010 

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 

US Domestic 

Measurement Subsystem 

Owner/ 

Contractor/Location 

Name/Type 

Anadarko 

Independence Hub (Semisubmersible) 

Anadarko 

Marco Polo (TLP) 

Anadarko 

NEPTUNE (Spar) 

Anadarko/Technip 

Boomvang (Truss Spar) 

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) 

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) 

"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 

Pressure/Temperature/Humidity 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 

Platform Position and Motions (0.00 Hz -0.01Hz)-within 190 

Nautical Miles of USCG Stations 

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

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

190 Nautical Miles of USCG Stations 

X (2) X 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-pnuematic Tensioners) X X 

Production Riser Stroke 

Riser and Pull Tube Monitoring 

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

Air Can Buoyancy Force X 

Air Can Riser Guide Compression X 

Tendon Tensions (TLP's only) X 

Steel Catenary Riser Inclination/Vibration 

Fiber Optic Long Base Strain Gauges 

X X X 

Hybrid Riser Tower Monitoring System 

Calm Buoy/OOL Monitoring System 

X X 

Ballast Control System X X X 

Independent Remote Monitoring System (IRMS) 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 X 

Draft 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 


Gunnison (Truss Spar) 


Nansen (Truss Spar) 


Red Hawk (Cell Spar) 

Gulf of Mexico 

TLP - Seastar 


Semisubmersible 



BP/Technip 

Holstein (Truss Spar) 

BP/Technip 

Horn Mountain (Truss Spar) 

BP/Technip 

Mad Dog (Truss Spar) 

BP/ABBL G 

Mariin (TLP) 



2


Table 2. Summary Table of Gulf of Mexico Floating Production Platforms equipped with BMT Integrated Marine 

Monitoring Systems – Part 2 

US Domestic 


Owner/ 


Name/Type 



Chevron/Spartec 

Genesis (Classic Spar) 


Spar 

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 

Chevron/Atlantia 

Typhoon (TLP-Seastar) 

Conoco/COP JIP 

Joliet (TLWP) 

ENI/Atlantia 

Allegheny (TLP-Seastar) 

X (5 

DO 

F) 

X 

(2) 

ENI/Atlantia 

Morpeth (TLP-Seastar) 

X (5 

DOF) 

ENI/McDermott 

Devils Tower (Truss Spar) 


Opti 

Murhpy/McDermott 

Front Runner(Truss Spar) 



Murphy/McDermott 

Medusa (Truss Spar) 


Spar 

X X X X X 

W&T/Atlantia 

Matterhorn (TLP-Seastar) 

X (3 

DOF) 

X (2) X X X X 

X X X X X 

Platform True Heading X X X X X 


Air Can ) 

X 


Air Can ) 

X X X 

Production Riser Tensions (Hydro-pnuematic Tensioners) X 

Production Riser Stroke X 


Air Can Buoyancy Force 

Air Can Riser Guide Compression 

X 

Tendon Tensions (TLP's only) 


Fiber Optic Long Base Strain Gauges 

Hybrid Riser Tower Monitoring System 


Ballast Control System 

Independent Remote Monitoring System (IRMS) 

X X X X X 

Mooring Line Tensions X X X X X X X X 

Draft 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 (MS- 

860) 

3


Table 3. Summary Table of Floating Production Platforms in Brazil, Malaysia, and West Africa, equipped with 

BMT Integrated Marine Monitoring Systems 

International 


2. Objectives of the IMMS 

Owner/ 


Name/Type 

Air Gap/Waves 

Wave Direction 

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

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 



X 



X X X X X 

Platform True Heading X X X 


Air Can ) 


Air Can ) 

Production Riser Tensions (Hydro-pnuematic Tensioners) 

Production Riser Stroke 


Air Can Buoyancy Force 

Air Can Riser Guide Compression 

X X 

Tendon Tensions (TLP's only) 


X X 

Fiber Optic Long Base Strain Gauges X 

Hybrid Riser Tower Monitoring System X X 


Ballast Control System 

Independent Remote Monitoring System (IRMS) 

X 

Mooring Line Tensions X X X X 

Draft X X X X 

Ballast Tank Levels X X X X 

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 

BP 

Greater Plutonio (FPSO) 

West Africa 

TLP 

West Africa 

TLP 

Malaysia 

Truss Spar 

Petrobras 

P-52 (FPSO) 

Husky/SBM-A 

White Rose (FPSO) 

Petrobras/SBM 

Espadarte (FPSO) 

4


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. 

3. Operational Decision Support 

Table 4. Overview of the Rationale for IMMS Measurements 

Operational Decision Support 

Measurement Subsystem Installation Running Riser Drilling Production 

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

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

W ind Speed and Direction Not Functional 

"Surface Current" 

Current Profile 

Bottom Current (Profile) 

Guidance on managing 

service vessel operations 


subsea operations 


subsea operations 

Pressure/Temperature/Humidity Not Functional 

Platform Attitude and Motions (0.0 

and 0.01 Hz -1Hz) 

Platform Position and Motions (0.00 

Hz -0.01Hz)-within 150 Nautical Miles 

of USCG Stations 

Platform True Heading (Low 

frequency yaw) 

Production Riser Tensions and 

Bending Moments 

TLP- check trim and list 

prior to tendon lock-off to 

ensure platform installed 

level 

Check Mooring Set Up 

and on SCR's to verify 

installed angle 

Check As Installed 

Heading and on SCR's to 

verify installed angle 

Guidance on managing Helicopter,service vessel, crane and heavy lift 

operations 

Identify excessive 

currents 


currents 

Not Functional Set Riser Tension 

Guidance on managing service vessel operations 


currents 


currents 

Forensic 

Engineering 

Estimate Run-Up; Assess 

wave damages; 

Characterize environment 

Estimate Run-Up; Assess 

wave damages; 

Characterize environment 

Assess Topsides 

damage;Characterize 

environment 

evaluate cause of mooring 

failures or observed platform 

Vortex Induced Motion 

Verification of Design 

Tools 

Characterize Environmental forcing 

functions 


functions 


functions 


functions-Validate Hull VIM Models 

Integrity 

Monitoring 

Input to Damage 

Prediction Models 







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 

5 

N/A 

N/A 

Advance storm forecasting for Helicopter,service vessel, crane and 

heavy lift operations 

Guidance on managing heavy lift operations 

Positioning Platform over subsea well heads 

Mooring Sy stem 

Adjustment in 

Anticipation of weather 

or high curents 

Positioning Platform over subsea well heads Mooring System 

Adjustment 

Manage riser tension 

fac tor 

Production Riser Stroke Not Functional Not Functional N/A 

Air Can pressures Not Functional Set Tension 

Manage riser tension 

fac tor 

W arn of Approach to 

Stops 

Maintain Tension and 

Identify sources of leaks 

Air Can Riser Guide Compression Not Functional N/A N/A N/A 

Tendon Tensions Set Tensions N/A N/A 

Mooring Line Tensions and Payout Set Tensions 

Draft 

Ballast Tank Levels 

Steel Catenary Riser 

Inclination/Vibration 

TLP - us e to verify 

installed tendon tensions 

TLP - us e to verify 

installed tendon tensions 

Verify SCR Installed 

inclination 

Positioning over 

subsea wellheads 

Positioning over 

subsea wellheads 

Maintain Tension and 

W eight Distribution 

Tension Adjustment for 

high currents and 

Hurricanes 

N/A N/A Ballast/Trim/Heel Control 

N/A N/A Ballast Trim Heel Control 

N/A N/A N/A 

Determ ine cause of riser 

loads 

Determ ine cause of riser 

loads 

Verify hurricane/storm 

intensity 

Estimate excitation of 

SCR's and production risers 


SCR's and Production 

Risers, Mooring loads 


SCR's 

identfy performance 

problem s 

identify excessive riser 

excursions; identify failure of 

B Cans to slip in guides 


of risers 


of risers 

Input to Fatigue 

Damage Prediction 

Models 

Input to Fatigue 

Damage Prediction 

Models 

N/A N/A 

Estimate Fatigue 

damage in SCR's; 

Verify Global Motion Models 

Foundations of Large 

tanks/Derrick 

Quasi static loads 

Verify Global Motion Models; VIM 

on Mooring 

Models 

Equipment 


Verify Riser Responses and fatigue 

models 

Explain Tension Loss N/A 

Assess loads on Buoyancy 

Cans 

investigate tendon failures 

Identify causes of Mooring 

Failures and quantify timeon-link 

for fatigue estimation 

establish causes of errors in 

ballast control 

establish causes of errors in 

ballast control 

help to identify reasons for 

component filure or 

degradation 

Estimate excitation 

of SCR's 

Riser Fatigue 

Damage 

Verify Riser Quasi Static 

N/A 

Responses 

Track integrity of 

chambers 

Assess Load Estimation M odels N/A 

Validate Tendon Tension Estimating 

Models 


Required for chracterization of hull 

Required for chracterization of hull 

verify Floater Motion induced 

response in SCR 

insure that CG is 

within proper limits; 

identify degradation 

in tendon anchors 

Track mooring line 

fatigue damage; 

anchor failures 

Identify sinkage due 

to leaks/collision 

damage 

Track Intact and 

Damaged Stability 

Estimate and Track 

SCR Fatigue


• 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. 

6

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 

7

- 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 

8


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 

9

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. 

SEA 

SURFACE 

Water 

Depth 

approx. 

1900m 

Long range horizontal 

ADCP 

MID-DEPTH. 28 measurement 

bins of 16m length 

Riser Mounted ADCP 

ADCP 468m ASB 

LMRP Mounted ADCP 

ADCP 20m ASB 

BOP & 

LMRP 

UPPER. ADCP 

30m below MSL 

UPPER. First bin: 

72m below MSL 

MID-DEPTH. Depth of last 

valid bin: 924m ASB / 976m 

below MSL 

MID-DEPTH. First bin: 

492m ASB 

SEABED. Last valid bin: 

476m ASB 

SEABED. First 

bin: 44m ASB 


UPPER. 33 measurement 


UPPER. Depth of last valid bin:1096m 

below MSL/ 804m ASB 

SEABED. 28 measurement 


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). 

10


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 

11


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 

12

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. 

13


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 

14


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) 

15


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. 

16

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 

17


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 

18


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 

19


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. 

20

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. 

21


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


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. 

10. Summary and Conclusions 

Figure 26. Buoyancy Can Supported (Spar) Riser Screen 

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 

Significant Wave Height Hs (ft) 

16 

14 

12 

10 

8 

6 

4 

2 

0 

1-Oct 

7-Oct 

13-Oct 

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, 

19-Oct 

Hs (AirGap Sensor) 

Hs (NDBC 42041) 

25-Oct 

31-Oct 

23


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 

info@scimar.com 

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/s 2 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 


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.

Operational displays. 

www.scimar.com 

info@scimar.com 


9835 Whithorn Drive 

Houston, TX 77095 

Ph: 281.858.8090 

Fx: 281.858.8898 

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). 


955 Borra Place, Suite 100 

Escondido, CA 92029 

Ph: 760.737.3505 

Fx: 760.737.0232

Integrated Marine Monitoring System - BMT Group

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