MODU Mooring In Australian Tropical Waters Guideline
MODU Mooringin Australian Tropical WatersGuidelineRevision 1 01/04/17
PREFACEThis guideline has been developed by industry to provide a consistent and common approach to MODUmooring exposed to cyclonic conditions in Australian tropical waters. Industry participants include Oil & GasOperators through APPEA drilling industry steering group (DISC), MODU mooring contractors throughInternational Association of Drilling Contractors (IADC) and mooring equipment and engineering contractors.The guideline is to be read in conjunction with the NOPSEMA information paper MODU Mooring systems incyclonic conditions [10], company mooring standards and procedures and well known industry codes (API,DNV etc.).DISCLAIMERAPPEA and its participants disclaim any liability of whatsoever nature for any damage (including injury ordeath) suffered by any company or person whomsoever as a result of or in connection with the use,application or implementation of this guideline or any part there of contained in this document.CONTRIBUTORSThe authors would like to acknowledge the industry contributors who were instrumental in writing thisGuideline: Woodside Inpex Chevron Quadrant Energy Shell Transocean Stena Drilling Atwood Oceanics Delmar Systems Viking Seatech Deep Sea Moorings DNV-GL Evan Zimmerman (TechnoNautic)REVIEW & UPDATESThis publication is intended to be ‘living‘, working document with feedback welcomed and incorporated into aregular review process and the guidelines updated where necessary or desirable.A feedback form to the editorial committee to provide comments, suggestions for additions or changes ornew information on the document can be found in Appendix F.MODU Mooring in Australian Tropical Waters GuidelinesPage 2 of 55
TABLE OF CONTENTS1A1A2A3DEFINITIONS AND ABBREVIATIONS . 6Definitions . 6Abbreviations . 7Use of Language. 822.12.2INTRODUCTION . 9How to use this document . 9Supporting Mooring Codes and Standards . 1133.13.23.33.4RISK SCREENING . 12Introduction . 12Philosophy of risk screening . 12Risk Screening Tests . 12MODU Mooring Risk Category . 1344.14.24.34.44.54.64.7RISK & ASSURANCE MANAGEMENT. 14Introduction . 14Principles . 14Objectives . 14Risk Assessment . 14Risk Evaluation . 15Risk Treatment. 16Risk Based Mitigation Activities . 1755.15.25.35.4MOORING DESIGN & ANALYSIS . 18Basis of Design Requirements . 18Mooring Design Scope of Work . 19Metocean Return Period Criteria . 21Risk Based Mitigation Activities . METOCEAN . 23Salient Oceanographic Features . 23Synoptic Meteorology . 23Winter Season . 23Summer Season . 23The Transition Seasons . 23Extreme Wind Conditions . 24Easterly Gales (Trade Wind Surge) . 24Tropical Cyclones . 24Squalls . 24Wave Climatology . 24Current Regime. 25Temperature and Salinity Distributions . 25Tidal range . 25Risk Based Mitigation Activities . 2677.17.27.3GEOTECHNICAL . 27Geology of the NWATW of Australia and Geohazards . 27Estimating anchor capacity in calcareous soils . 27Anchor installation and testing requirements . 28MODU Mooring in Australian Tropical Waters GuidelinesPage 3 of 55
7.47.5Sharing geotechnical information . 28Risk Based Mitigation Activities . 2988.18.28.38.48.58.6MOORING EQUIPMENT . 30Scope . 30Manufacturing, Testing & Certification . 30Equipment Storage . 30Maintenance & Service History . 30Use of Fibre Mooring Lines . 31Risk Based Mitigation Activities . 3299.19.29.39.49.59.69.79.89.99.10MOORING INSPECTION . 33Scope . 33Equipment Inspection Standards & Procedures . 33Inspector Competence & Training . 33Chain, Accessories & Wire Rope Visual Inspection . 33Chain, Accessories & Wire Rope Magnetic Particle Inspection . 34Fibre Rope Inspection . 35Wire Rope Sockets . 35Fibre Rope Eye Splice . 35Pre & Post Tropical Cyclone Inspection Requirements . 36Risk Based Mitigation Activities . 371010.110.210.310.410.510.610.710.8MOORING OPERATIONS . 38Scope . 38Operations Standards & Procedures . 38Vessel and MODU Personnel Competence & Training . 38Mooring System Rigging and Handling . 38Mooring Installation & Recovery Procedures . 39Marine Operations . 40Tropical Cyclone Preparation & Response . 40Risk Based Mitigation Activities . 42REFERENCES . 43APPENDIX A: MODU MOORING SYSTEM PERFORMANCE STANDARD . 44APPENDIX B: MODU CYCLONE PREPARATION CHECKLIST . 48APPENDIX C: MODU MOORING FAILURE FLOW CHART . 50APPENDIX D: EXAMPLE MOORING BASIS OF DESIGN FORM . 51APPENDIX E: MODU MOORING WORKFLOW GUIDANCE . 52Step 1 – Collect information . 52Step 2 – Determine MODU mooring risk category . 53Step 3 – Review Risk Mitigation Measures and determine metocean Return Period . 53Step 4 – Conduct Mooring Analysis . 54Step 5 – Conduct Risk Assessment . 54APPENDIX F: FEEDBACK FORM . 55MODU Mooring in Australian Tropical Waters GuidelinesPage 4 of 55
DOCUMENT REVISION HISTORYREVIEW STATUS DETAILED REVISION INFORMATIONRevisionDescriptionDatePrepared byApproved byASplit document review by Block 1 & 2 Groups10/06/16APPEA DISCAPPEA DISCBCompiled document review by TechnoNautic,Block 1, Block 2 & DNVGL.08/07/16APPEA DISCAPPEA DISC0Final approved version01/11/16APPEA DISCAPPEA DISC1Feedback Form added as Appendix F1/04/16APPEA DISCAPPEA DISCMODU Mooring in Australian Tropical Waters GuidelinesPage 5 of 55
1A1DEFINITIONS AND ABBREVIATIONSDefinitionsTermDefinitionClose ProximityRefers to distance between the MODU and surface and/or subseaassets, including areas of environmental significance, which areclose enough to be considered a mooring risk. The risk dependson the type/value/manning of asset as well as MODU mooringdesign certainty and equipment assurance. The distance dependson the mooring risk and company risk tolerance. As a rule ofthumb a distance between MODU mooring centre and high valueasset of 10km–20km may be considered “Close Proximity”.Limit State AnalysisRelationship between metocean data return period and mooringfactor of safety. The purpose of this data is to estimate the returnperiod (in years) corresponding to mooring failure.OperatorOperator of the MODU as per NOPSEMA definition.TitleholderHolder of the exploration or production permit as per NOPSEMAdefinition.MODU Mooring in Australian Tropical Waters GuidelinesPage 6 of 55
A2AbbreviationsAbbreviationDefinitionALARPAs Low As Reasonably PracticalAPIAmerican Petroleum InstituteAPPEAAustralian Petroleum Production & Exploration AssociationBODBasis of DesignBOE/DBarrels of Oil Equivalent per DayBOMBureau of MeteorologyBOPBlow Out PreventerCPTCone Penetration TestDISCDrilling Industry Steering CommitteeDNV GLDet Norske Veritas Germanische LloydFOSFactor of SafetyGOMOGuidelines for Offshore Marine OperationsIACSInternational Association of Classification SocietiesIADCInternational Association of Drilling ContractorsICAPInspection & Condition Assessment PlanISOInternational Standards OrganisationJIPJoint Industry ProjectMAEMajor Accident EventMMATWMODU Mooring in Australian Tropical WatersMOCManagement of ChangeMODUMobile Offshore Drilling UnitMBLMinimum Breaking LoadMBSMinimum Breaking StrengthMPIMagnetic Particle InspectionNDTNon Destructive TestingNGINorwegian Geotechnical InstituteNOPSEMANational Offshore Petroleum Safety & Environmental Management AuthorityNWATWNorth West Australian Tropical WatersMODU Mooring in Australian Tropical Waters GuidelinesPage 7 of 55
A3OEMOriginal Equipment ManufacturerOPGGS(S)Offshore Petroleum and Greenhouse Gas Storage (Safety)OSIGOffshore Site Investigation and GeotechnicsPCCPermanent Chain ChaserPCPPermanent Chain PendentPMSPlanned Maintenance SystemQAQCQuality Assurance & Quality ControlQRAQuantitative Risk AssessmentRAOResponse Amplitude OperatorRCSRecognised Classification SocietyRPReturn PeriodROVRemotely Operated VehicleSLFSingle Line FailureSUTSociety for Underwater TechnologyUHCUltimate Holding CapacityUVUltra-VioletUse of LanguageTermDefinitionConsiderRefers to risk based mitigation activities identified in this guidelinethat may be applied when implementing this guideline.RecommendedRefers to risk based mitigation activities identified in this guidelinethat ought to be applied when implementing this guideline.Highly RecommendedRefers to risk based mitigation activities identified in this guidelinethat ought be applied when implementing this guideline.Justification should be documented where the recommendedactivity is not adopted.MayCompliance is discretionary and is to be considered.ShouldCompliance is discretionary but is recommended.Shall/MustCompliance with the requirement is mandatory.MODU Mooring in Australian Tropical Waters GuidelinesPage 8 of 55
2INTRODUCTIONDescribed below is guidance on MODU mooring in Australian tropical waters (MMATW). Due to a loss ofstation keeping event to a MODU in 2015, and in response to the investigation and NOPSEMA collaboration,APPEA has agreed to produce and publish this guideline to provide greater clarity on mooring a MODU incyclonic conditions in Australian tropical waters. The purpose of this document is to: Provide a consistent approach to mooring design, installation and equipment assurance. A framework to improving station keeping reliability and performance in local conditions which areunique to this region.2.1How to use this documentThis document is intended to be read in conjunction with industry standards, codes and recommendedpractices such as API and DNV and company standards (if applicable).The document provides recommendations and guidance on MODU mooring risk based on a risk screeningprocess which categorises the MODU mooring risk as either Low, Medium or High (see Section 3). Based onthe MODU mooring risk category, guidance and recommendations are provided throughout the documentunder the subheading of ‘Risk Based Mitigation Activities’.Figure 1 below shows the intended workflow for MODU mooring assessment.Appendix E provides guidance on the below workflow.MODU Mooring in Australian Tropical Waters GuidelinesPage 9 of 55
StartCollect information:metocean data,location, soil andassociated anchorUHC, MODU,mooring equipmentDefine MODU MooringRisk Category(Section 3)Determineminimummetocean ReturnPeriodrequirement(Section 5.3)Consider the following:1) Revise mooringdesign to reducemooring loads and/orincrease equipmentMBS2) Satisfy RiskMitigation Test(Section 3.3.3) toreduce Mooring RiskCategory andassociated metoceanreturn period.3) Drill outside ofcyclone seasonReview RiskMitigation Measures(see Tables inSections 4.0 to 10.0)Conduct MooringAnalysisNoMooringAnalysis passesAPI RP 2SK?YesConduct RiskAssessmentRisk tolerableand ALARP?NoYesEndFigure 1: Workflow of MODU mooring assessmentMODU Mooring in Australian Tropical Waters GuidelinesPage 10 of 55
2.2Supporting Mooring Codes and StandardsThe primary mooring codes, standards and recommended practices referenced throughout his documentare: API RP 2SK API RP 2SM API RP 2I DNVGL-OS-E301 DNVGL-OS-E302 DNVGL-OS-E303 DNVGL-OS-E304 Guidelines for Offshore Marine Operations (GOMO)MODU Mooring in Australian Tropical Waters GuidelinesPage 11 of 55
3RISK SCREENING3.1IntroductionThe purpose of this section is to provide guidance on characterising the MODU mooring risk as either: Low,Medium or High. This process is iterative and may be revisited during the design of MODU mooring. The riskbased recommendations throughout this document are based on these three risk categories.3.2Philosophy of risk screeningThe risk screening comprises three tests:1. Consequence test – Based on the proximity of MODU (drill site) to high value assets.2. Likelihood test – Based on season of operation (cyclonic or non-cyclonic)3. Risk mitigation test – Based on the quality of information available about the MODU, the mooringequipment and the drill site which allows for mooring risk to be mitigated through:a. Reliable assessment of mooring load and performance;b. Reliable assessment of mooring equipment strength;c. Reliable assessment of anchor holding capacity.The MODU mooring risk category is determined by the above tests.The consequence and likelihood tests provide an initial risk category depending on the location of proposeddrill centre and season (cyclonic or non-cyclonic). The risk mitigation tests (Section 3.3.3) aim to reduce theinitial MODU mooring risk category for instances where there is sufficient information available about theproposed drill site and MODU to achieve a high certainty of mooring loads and performance of mooringsystem.Changing the risk category for a particular location can be done by changing the season of operation(associated metocean conditions) and/or by satisfying the risk mitigation tests.3.3Risk Screening Tests3.3.1Consequence Test – Proximity to assetsIs the drill centre in close proximity to high economic or HSE exposure assets?Guidance: Examples of high values assets in NWS: Jacketed platforms Manned structures (OHS Risk) Gas Export trunklines Heritage marine parks and sanctuary zones (Environmental Risk)See Section A1 for definition of “close proximity”.3.3.2Likelihood Test – Season of operationIs the drilling campaign expected to extend into cyclone season?Guidance: Cyclone season is from 1 November until 30 April, non-cyclone season is from 1 May to 31October.3.3.3Risk Mitigation TestsIs there enough information about the site and MODU to achieve a high level of certainty that mooring riskscan be mitigated to a level that is ALARP?Note: All three risk mitigation tests (A, B and C) have to be satisfied.MODU Mooring in Australian Tropical Waters GuidelinesPage 12 of 55
3.3.3.1 Mitigation Test A – Reliability of mooring analysisIs metocean data appropriate for location, and have MODU characteristics been accurately determined for areliable assessment of mooring load and performance?Guidance: Consider the following: Is site specific metocean data available? Is there sufficient information about MODU characteristics (RAO, force coefficients)? Does the condition of the MODU accurately reflect the tested condition for which MODUcharacteristics have been determined, i.e. no major modifications to MODU geometry,displacement, mass distribution?See Section 5 for more information on MODU mooring analysis considerations.3.3.3.2 Mitigation Test B – Mooring equipment assuranceIs there a high level of confidence in the mooring equipment minimum break strength (MBS) to assessresistance to mooring loads?Guidance: Consider the following when evaluating certainty of mooring equipment integrity and MBS: Are original mooring equipment certificates available and traceable?Are service history records and recent inspection reports available for all equipment?Has mooring equipment been inspected after the most recent campaign?Have non-destructive tests been recently carried out for connecting hardware?If wires and fibres (if applicable) are not near new, have destruction tests been completed recently?See Section 8 and Section 9 for more information on mooring equipment and inspection considerations.3.3.3.3 Mitigation Test C – Reliability of anchor holding capacityIs there a high level of confidence in the anchor holding capacity to resist mooring loads?Guidance: Consider the following when evaluating anchor UHC certainty Is there access to site specific soil strength data with information regarding presence and depth ofcemented layers? Will an anchor analysis be completed using site specific soil data? Will anchors be proof-tested after installation, either with AHV and/or cross-tensioned with rigwinches?See Section 7 for more information on geotechnical considerations.3.4MODU Mooring Risk CategoryOnce the above risk screening tests have been reviewed, the below table can be used to determine theMODU mooring risk category.Consequence Test: Is the drill centre in close proximity to high economic or HSE exposure ediumNon-cycloneseasonLowMediumLowFailPassRisk Mitigation Test: Have tests A, B and C been satisfied?Figure 2: MODU mooring risk categoryMODU Mooring in Australian Tropical Waters GuidelinesPage 13 of 55
4RISK & ASSURANCE MANAGEMENT4.1IntroductionMooring design should be risk assessed on a case by case basis either qualitatively or quantitativelydepending on the risk level. The mooring system utilised should be associated with a tolerable risk.4.2PrinciplesRisk is defined as:Risk Probability (of risk event occurring) Consequences (associated with that event)Risk can be reduced through prevention (reducing probability), or mitigation (reducing consequence).The consequences associated with MODU mooring failure can be: Health and safety Environmental Financial Corporate reputation and brand Legal and compliance Social and cultural4.3ObjectivesThe objective of undertaking a mooring risk assessment is to: Estimate the likelihood of risk events taking place Assess the consequences of risk events Rank the risk of the various risk events Identify risk reduction options prior to finalising the mooring design and installing the mooring system. Confirm that risk associated with major accident event has been reduced to ALARPRisk events are typically associated with a loss of station keeping, either due to failure of mooring line, oranchor dragging, which results in uncontrolled MODU drift. Risk of damage to subsea assets due to mooringline failing and falling though the water column should also be considered.4.4Risk AssessmentA suitable risk assessment should be undertaken for a specific MODU mooring operation. The type of riskassessment and associated level of detail depends on the MODU mooring risk category.For the purpose of this document, risk assessments are characterised as either quantitative or qualitative.4.4.1Quantitative Risk AssessmentA quantitative risk assessment (QRA) involves calculating a numerical value for the likelihood (probability) ofa risk event taking place through the use of probability theory. The probability is then combined with theconsequence in order to determine the risk.The probability associated with a risk event is determined by: Probability of mooring failure resulting in MODU drift (Pf) Probability of impact between MODU and subsea or surface infrastructure (Pi) Probability of damage resulting from impact (Pd)The value consequence of damage including lost production (C)MODU Mooring in Australian Tropical Waters GuidelinesPage 14 of 55
The risk can then be expressed as:Risk Pf x Pi x Pd x CAdditional probability factors can be incorporated into the above equation to account for certainty of: MODUmooring loads, anchor UHC and mooring equipment breaking strength.Implementing risk based mitigation activities can reduce the risk of probability of failure (Pf).The advantage of quantifying the probability of a risk event is that it reduces the potential for subjectivity andenables comparison between mooring design options.4.4.1.1 Required inputsIn order to undertake a quantitative mooring risk assessment, the following inputs may be required: Limit state results from the mooring analysis which consider a wide range of environmental returnperiods. The limit state results should be plotted (FOS vs RP) for both the anchor holding FOS andmooring line FOS. Information on nearby surface and subsea infrastructure: Map which can be used to extract the distance and heading between MODU and nearbyinfrastructure. Hydrocarbon throughputs of nearby infrastructure, or in lieu of this, an estimate of the financialconsequence associated with collision event between MODU and the particular infrastructure. Size and construction of pipelines and flowlines Map of important environmental features in close proximity to the MODU location, such as high valuemarine and shore habitats. Source and methodology of metocean data and source of vessel characteristics (certainty of MODUmooring loads). Source of geotechnical information and methodology of determining anchor UHC (certainty of anchorUHC). Mooring equipment information such as certification, inspection reports, history of use (certainty ofmooring equipment MBS).Significantly high value infrastructure or environmental features which are not in close proximity should alsobe considered.4.4.2Qualitative Risk AssessmentA qualitative risk assessment does not involve the detailed calculation of probability of risk events. However,the likelihood of risk events, and the associated consequence, should still be addressed.The likelihood can be assessed based on company and local industry experience and historical data.Probability of mooring failure can be simply es
API RP 2SK API RP 2SM API RP 2I DNVGL-OS-E301 DNVGL-OS-E302 DNVGL-OS-E303 DNVGL-OS-E304 Guidelines for Offshore Marine Operations (GOMO) MODU Mooring in Australian Tropical Waters Guidelines Page 12 of 55 3 RISK SCREENING 3.1 Introduction The purpose of this section is to provide guidance on
MODU Code and be issued a MODU Safety Certificate (2009). §4.0 of these MOU Standards contains the Administrator’s interpretations of the 2009 MODU Code. .2 A unit constructed on or after 01 May 1991 and prior to 01 January 2012, must meet the requirements of the 1989 MODU Code and be issued a MODU Safety Certificate (1989).
82 "MODU Code 1989" January 1993 87 MODU Code" 1979 & 1989 April 1994 150 MODU Annual Safety Inspection July 2007 289 Bottom Surveys of Mobile Offshore Units (Drilling and non-Drilling) certificated under MODU Code adoption. April 2014 292 Mobile OFFshore Units (MOU) - Nondescript Units July 2014 328 Validity of some certificates for MODU/MOU .
API RP 2SK–MODU and FPS (1997, 2005) Design Environment: 5 year (away from other structures) 10 year (close to other structures) The 1997 Revision was Based on Mooring Code Calibration JIP (1995) (2) International Standard Organizat
by time domain potential flow theory, and the safety of the ship is analyzed and verified. The dock mooring design is carried out to calculate the mooring force of each cable based on the wave load and compare it with the specification value to verify the reliability of the mooring method. The main dimensions of the LNG ship are shown in Table 1.
API-RP-2SK recommends equal or higher design strength than mooring line, [3]. The IEC support structure design is consistent with other mooring codes. Anchors or foundations design is of primary importance for a good mooring system design. Compar-ison of anchor holding capacity design safet
Australian tropical savanna factsheet Seasonal changes in the Australian tropical savanna People often refer to two seasons in the tropical savanna; the wet season and the dry season. The plants and animals are adapted to these changes in rainfall. They are able
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