HSE: OTO 2000/091 Accident statistics for mobile offshore units on

111 Pages·2001·0.54 MB·English

HSE
Health & Safety
Executive
ACCIDENT STATISTICS FOR
MOBILE OFFSHORE UNITS ON
THE UK CONTINENTAL SHELF
1980-1998
Prepared by
Det Norske Veritas
for the Health and Safety Executive
OFFSHORE TECHNOLOGY REPORT
2000/091
HSE
Health & Safety
Executive
ACCIDENT STATISTICS FOR
MOBILE OFFSHORE UNITS ON
THE UK CONTINENTAL SHELF
1980-1998
Espen Funnemark
Det Norske Veritas
Veritasvn
N-1322 Høvik
NORWAY
HSE BOOKS
©Crown copyright 2001
Applications for reproduction should be made in writing to:
Copyright Unit, Her Majesty’s Stationery Office,
St Clements House, 2-16 Colegate, Norwich NR3 1BQ
First published 2001
ISBN 0 7176 1953 2
All rights reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted in any
form or by any means (electronic, mechanical,
photocopying, recording or otherwise) without the prior
written permission of the copyright owner.
This report is made available by the Health and Safety Executive
as part of a series of reports of work which has been supported
by funds provided by the Executive. Neither the Executive, nor
the contractors concerned assume any liability for the reports nor
do they necessarily reflect the views or policy of the Executive.
TECHNICAL REPORT
Table of Contents Page
1 EXECUTIVE SUMMARY..........................................................................................1
1.1 Introduction and background 1
1.2 Confidentiality 1
1.3 Objectives, results and conclusions 2
2 INTRODUCTION.......................................................................................................5
3 OBJECTIVES AND SCOPE OF WORK....................................................................6
4 EXPOSURE DATA.....................................................................................................7
4.1 Mobile offshore drilling units (MODUs) 7
4.2 Mobile Production Units (MOPUs) 8
4.3 Monohull units 10
4.4 Accommodation Units 12
5 INCIDENT REPORTING IN UK WATERS............................................................13
6 SUN SAFETY SYSTEM DATABASE....................................................................14
6.1 Available data 14
6.1.1 Incident category codes 15
6.1.2 Operation codes 16
6.1.3 Dangerous occurrence type codes 16
6.1.4 Accident kind codes 17
6.2 Event classification and coding principles 17
6.3 Result of interrogation 19
6.3.1 All mobile units 22
6.3.2 Mobile Drilling Units (MODUs) 23
6.3.3 Mobile Production Units (MOPUs) 32
6.3.4 Monohull Units 38
6.3.4.1 FPSOs 39
6.3.4.2 FSUs 43
6.3.5 Accommodation Units 46
7 FOCUS/SHIELD DATABASE.................................................................................49
7.1 Result of interrogation 49
8 THE MAIB DATABASE..........................................................................................50
8.1 Available data and reporting 50
8.2 Result of interrogation 51

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9 WOAD.......................................................................................................................53
9.1 Available data 53
9.2 Result of interrogation 54
9.2.1 All mobile units 56
9.2.2 Mobile Drilling Units (MODUs) 57
9.2.2.1 Drilling jackups and semisubmersibles 57
9.2.2.2 Drill ships 62
9.2.3 Mobile Production Units (MOPUs) 63
9.2.3.1 Production semisubmersibles 63
9.2.3.2 Tension-leg platforms 64
9.2.4 Monohull Units 64
9.2.4.1 FPSOs 64
9.2.4.2 FSUs 64
9.2.5 Accommodation Units 65
10 BLOWOUT DATABASE.........................................................................................66
11 ACCIDENT STATISTICS........................................................................................67
11.1 Accident frequencies, All databases combined 67
11.2 Occurrence frequencies, All databases combined 69
11.2.1 Mobile Drilling Units (MODUs) 70
11.2.2 Mobile Production Units (MOPUs) 79
11.2.3 Monohull Units 85
11.2.3.1 FPSOs 86
11.2.3.2 FSUs 90
11.2.4 Accommodation Units 93
11.3 Frequencies, mobile units on NCS 96
11.4 Frequencies, fixed units on NCS 96
12 CONCLUSIONS........................................................................................................97
13 REFERENCES...........................................................................................................98

Appendix A HSE Sun Safety System; Dangerous Occurrence Type Codes

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TECHNICAL REPORT
1 EXECUTIVE SUMMARY
1.1 Introduction and background
In a recent project, four databases holding information about UK Continental Shelf (UKCS)
semi-submersible flooding incidents were interrogated. The survey revealed that that none of
them had a complete recording of such incidents. In addition, it was identified that there were
incidents which were not recorded in any of these sources. Consequently, the event frequencies
being obtained varied with the availability of sources. Obviously, there was no reason to believe
that the situation and figures for other types of events on mobile units should be any different.
Hence, it was proposed to initiate a similar type of project, but addressing all types of risks to
mobile units.
Prior to 1991 the regulation of offshore safety was the role of the Department of Energy, DEn.
During the period that the DEn was in place, data concerning incidents and accidents on offshore
installations within the UKCS was passed to the WOAD databank. From 1991 the role of
regulation of offshore safety passed to the HSE and very little, if any, data was passed to
WOAD. The Health And Safety At Work Act, HASAWA, Section 28, Disclosure of
Information, being interpreted at the time by the HSE so as to prevent the transfer of such
information. As a consequence, from 1991 until very recently no UKCS offshore installation
incident data has been made available to WOAD by the HSE. Therefore current WOAD risk
estimates exclude incidents and accidents on the UKCS except for those where adequate quality
information has been made available in the public domain.
A recent HSE legislative review of Section 28 allows, conditionally, the transfer of such data
from the HSE to WOAD. Provided that the project is in line with the general function of the
HSE "To secure the health, safety and welfare of persons at work" then it will not be in
contravention of HASAWA. This project has been accepted by the Open Government Unit of
the HSE as fulfilling that condition and in addition confidentiality is protected in that the
information so transferred has been "ring fenced".

1.2 Confidentiality
In order to ensure that the final results of the project were accurate and in line with the Quality
Control requirements of the WOAD databank it was necessary to obtain "raw" data from each of
the Databases interrogated. Raw data being defined as the data concerning a specific incident
which identified the installation, operator, location, date and time. The data so obtained enabled
quality checks to be undertaken on the different databases to prevent double counting of an
incident or accident.
It is a condition of the contract between the HSE and DNV, the custodians of the WOAD
databank, that any information so obtained will only be exported in a non attributable form to
protect confidentiality. That is, any request for data obtained by WOAD as a result of this
project will result in data being supplied which is non attributable and will not allow
identification of the name of the installation, company, location, date or time of an incident. It
will thus be impossible to pinpoint the installation or operator by any means.
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1.3 Objectives, results and conclusions
The main objective of the project is to obtain complete statistics (i.e. accident frequencies) for
accidents and incidents having occurred on mobile units engaged in the oil and gas activities on
the UKCS in the period 1980-98. Mobile units in this project are defined as comprising semi-
submersibles, jackups, ships and tension-leg platforms engaged in drilling, accommodation,
production and storage.
The results from this study would serve as a reference document for data to be used in future
Risk Assessments of offshore mobile units and furthermore, be a valuable reference document
for UK Health & Safety Executive (HSE)/ Offshore Safety Division (OSD) when reviewing
Safety Cases.
To fulfil this objective, relevant databases were interrogated with respect to both population and
accident data. This forms a complete data basis for obtaining comprehensive accident statistics
for the said type of units, geographical area and time period. The following databases were
selected for interrogation:
• FOCUS (UK HSE - Field Operations Division)
• Sun Safety System (UK HSE-Offshore Safety Division), SSS
• MAIB accident database (UK Marine Accidents Investigation Bureau)
• Offshore Blowout Database (SINTEF, Norway)
• Worldwide Offshore Accident Databank WOAD (Det Norske Veritas (DNV), Norway)

By combining and merging the results from the interrogation of the three databases, SSS, MAIB
and WOAD, the accident frequencies for mobile units in the UKCS in the period 1980-98 are
estimated. The other two databases did not contain information about accidents beyond that
which was already reported. In the two following tables the accident frequencies (i.e. number of
accidents per unit year) are given per type of installation, period and data source. N denotes
number of accidents and F denotes frequency, i.e. number of accidents per unit and year. The
source All databases combined refers to the database obtained by pooling the databases WOAD,
SSS and MAIB and removing the overlapping records. The data are presented for WOAD and
SSS separately due to the amount of data in these databases. The information contained in MAIB
does not contribute significantly to the results.

The result after having interrogated the databases and removing overlapping records is shown in
an Excel spreadsheet, which may be downloaded from HSE’s Internet Home Page
www.hse.gov.uk , documenting a total of 2406 events comprising accidents, hazardous situations
and near-misses. Note: Best efforts have been made to ensure complete anonymity within the
free text associated with each incident. However, it is possible that within the 2406 incidents
some anonymisation has been missed.
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Table 1 Mobile drilling units (MODUs) and mobile production units (MOPUs). Accident
frequencies (per unit year). UKCS, 1980-98.
MODUs MOPUs
Source-> WOAD SSS All databases WOAD SSS All databases
Period combined combined
1980-89 0.087 0.991 1.053 0.3 2.519 2.69
1990-98 0.113 2.323 2.425 0.096 1.968 2.007
1980-98 0.1 1.685 1.765 0.159 2.14 2.219

Table 2 Monohulls and all mobile units. Accidents frequencies (per unit year). UKCS,
1980-98.
Monohulls All mobiles
Source-> WOAD SSS All databases WOAD SSS All databases
Period combined combined
1980-89 - 0.414 0.414 0.094 1.043 1.108
1990-98 0.139 2.004 2.142 0.113 2.278 2.373
1980-98 0.117 1.748 1.864 0.105 1.715 1.796

The main conclusions from the work undertaken in this project are summarised below.

• The event frequencies strongly vary with the source being used
As identified in the recent project on semi-submersibles, this project also clearly shows that the
event frequencies being obtained strongly depend on which database is being interrogated.

• The main source for accident and incident information being available for the UKCS
offshore industry should be the HSE’s Sun Safety System (SSS)
Due to the accident reporting requirements for mobile units on the UK Continental Shelf
(UKCS), the main source for accident and incident information being available for the UKCS
offshore industry should be the HSE’s Sun Safety System (SSS). The interrogation of SSS in this
project showed that the database contains information for accidents and incidents ranging from
hazardous situations and working accidents with no consequences to severe damage and total
loss of units.

• Large difference in number of accidents between WOAD and SSS
When comparing the information held by DNV’s Worldwide Offshore Accident Databank
(WOAD) and SSS, there is a big difference in number of accidents. This is mainly explained by
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the fact that WOAD receives information about accidents through publicly available sources,
which in most cases only addresses events with large consequences. However, if considering the
Norwegian Continental Shelf (NCS), WOAD contains information about accidents and incidents
on the same level as SSS on the UKCS, due to an arrangement between the Norwegian
Petroleum Directorate and DNV for transferring information to WOAD.

• Increase in event frequencies when merging all databases together
If all mobile units are considered for the period 1990-98, then this study demonstrates a total
accident frequency of 2.3 per installation per year. This figure is a factor about 20 times higher
than that which is obtained from the publicly available database, WOAD.

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2 INTRODUCTION
In a recent project (ref. /1/), four databases holding information about UK Continental Shelf
(UKCS) semi-submersible flooding incidents were interrogated. These were UK Health & Safety
(HSE) - Field Operations Division’s (HSE-FOD) “FOCUS” database, HSE-OSD’s “Sun Safety
System” database, Marine Accidents Investigation Bureau’s (MAIB) accident database, and Det
Norske Veritas’ (DNV) “Worldwide Offshore Accident Databank”, WOAD”. The survey
revealed that that none of them had a complete recording of such incidents. In addition, it was
identified that there were incidents that were not recorded in any of these sources. Consequently,
the event frequencies being obtained varied with the availability of sources.
Obviously, there is no reason to believe that the situation and figures for other types of risks to
mobile units are any different compared to the one addressed in that project. Hence, it was
proposed to initiate a similar type of project, but addressing all types of risks to mobile units.
This report documents the results from this project.
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