NATIONAL OFFSHORE SAFETY ADVISORY COMMITTEE MEETING TOWING OF

NATIONAL OFFSHORE SAFETY ADVISORY COMMITTEE MEETING TOWING OF MOBILE OFFSHORE DRILLING UNITS A Marine Surveyor’s Perspective While Representing Underwriters’ Interests April 18, 2013 S. Douglas Devoy Executive Vice President / Director

Marine Warranty Surveyor Role for Tow Approval • Represent Underwriters/Comply with Marine Warranty in Policy • Review Rig Move / Towage Plan/ Make recommendations to reduce risk • Review Route / Time of Year/ Met Ocean Conditions • Review Inspect Towage Vessels / Make recommendations • Review Contingency Plans • Issue Towage Recommendations / Certificate

Drilling Contractor Rig Move Responsibility • Determine that rig is suitable to be placed under wet towage on this particular route, time of year and weather to be expected • Verify that rig will be operating in compliance with approved Rig’s Operations Manual / Contractors Rig Move Procedures Determination of Towage Type • Field Move • Extended Field Move • Ocean Towage

TYPES OF MODU’S Classes of Mobile Offshore Drilling Units • Drill Ships • Semi-Submersible Drilling Units • Jack-Up Drilling Units

TYPES OF MODU’S Drillship • Drill ship is self-propelled with full marine crew • Normally not towed or subject to any MWS approval

TYPES OF MODU’S Semi-Submersible Drilling Unit • Either self-propelled, propulsion assist or non self-propelled • Subject to Marine Warranty in policy • Subject to Marine Warranty Surveyor recommendations and approval • Extremely robust MODU with ballast down capability in event of heavy weather

TYPES OF MODU’S Jack-Up Drilling Unit • Independent Leg Jack-Up Drilling Unit • Subject to Marine Warranty in policy • Subject to Marine Warranty Surveyor recommendations and approval

Approval Process for Extended Field Moves / Specialized Towages

ANALYSIS OF A WET TOWAGE APPROVAL For this presentation we will concentrate on the Risk of Wet Towage of Independent Leg Jack-Up Drilling Unit, specifically a Marathon Letourneau 116 -C from Yangon, Myanmar to Singapore in the month of March.

ANALYSIS OF A WET TOWAGE APPROVAL Physical Damage Risks During Wet Tow • Weather • Tug Failure • Rig Impact from Tugs • Tow Line Failure / Rigging Poor Condition • Loss of Stability • Flooding and Capsize

ANALYSIS OF A WET TOWAGE APPROVAL Wet Towage/ Field Move/ Extended Field Move Standard question that is asked prior to the wet tow: WHAT ARE THE OPERATIONS MANUAL MAXIMUM DESIGN MET-OCEAN WEATHER CONDITIONS FOR THE WET TOW OF THE MODU? Answer: 70 knot winds or 100 Knot Winds

ANALYSIS OF A WET TOWAGE APPROVAL Operations Manual – Afloat Mode

ANALYSIS OF A WET TOWAGE APPROVAL Operations Manual – Afloat Mode

ANALYSIS OF A WET TOWAGE APPROVAL

ANALYSIS OF A WET TOWAGE APPROVAL Wet Towage/ Field Move/ Extended Field Move What question should be asked prior to the wet tow: WHAT ARE THE ACCEPTABLE WEATHER/RIG LIMITS Answer: FOR THE WET TOW OF THE MODU? • Max. Allowable Roll Angle – does not exceed 6 degrees • Max. Allowed Pitch Angle – does not exceed 6 degrees • Max. Significant Wave Height – does not exceed 4. 0 m

ANALYSIS OF A WET TOWAGE APPROVAL Seasonal Events • Aerospace & Marine International – METEVENT Calendar – Chart of Marine Meteorological Events was referenced to asses any seasonal events that could impact transit of the MODU when departing in March.

SEASONAL EVENTS AMI METEVENT CALENDAR

ANALYSIS OF A WET TOWAGE APPROVAL Wet Towage/ Field Move/ Extended Field Move HOW CAN ACCEPTABLE WEATHER CONDITIONS FOR TOW BE DETERMINED? SAFETRANS A tool used to determine likely environment that could occur during the towage.

ANALYSIS OF A WET TOWAGE APPROVAL Safe. Trans • An integrated PC tool used to design / analyze marine transports and installations of major facilities. • Used to determine risk for dry transportations and wet tows using vessels of virtually any shape and size. • Incorporating all of these variables allows Matthews. Daniel to accurately calculate the performance of the vessel under the influence of weather, taking into account captain's decisions to alter course, avoid storms or proceed to safe haven.

ANALYSIS OF A WET TOWAGE APPROVAL Safe. Trans • Worldwide weather database, tropical revolving-storm database and a forecast database. • Up to 7 days of forecasting is available in the program for the Captain's Decision Mimic (CDM). CDM is an expert system which simulates the captain's decisions on a tow, given the present conditions and the forecast, in an effort to avoid bad weather.

ANALYSIS OF A WET TOWAGE APPROVAL Safe. Trans – Methodology Using two separate modules, tows can be modeled within Safe. Trans to evaluate the true nature of the risk of proceeding with the towage • Voyage Motion Climate (VMC) • Monte Carlo Simulator (MCS)

ANALYSIS OF A WET TOWAGE APPROVAL Safe. Trans Methodology • Voyage Motion Climate (VMC) § Compute long-term statistical data on the basis of wave scatter diagrams § Statistical computation of motion, acceleration, load, tow force and many other conditions within the database used to compute voyage statistics and present it on Weibull graphics.

ANALYSIS OF A WET TOWAGE APPROVAL Safe. Trans Methodology • Monte Carlo Simulator (MCS) § When given a historic starting date, computes the voyage statistics on the basis of motion, acceleration, load, tow force and many other conditions within the database. § Allows Safe. Trans to apply weather routing while still accurately modeling the tow.

SAFETRANS ROUTE MYANMAR TO SINGAPORE

VOYAGE MOTION CLIMATE (VMC) SUMMARY OF VOYAGE – MARCH

MONTE CARLO SIMULATIONS (MCS) SIGNIFICANT WAVE HEIGHT, HISTOGRAM PLOT

MONTE CARLO SIMULATIONS (MCS) SIGNIFICANT WAVE HEIGHT, TOTAL

ANALYSIS OF A WET TOWAGE APPROVAL Results A number of factors were reviewed to determine the approvability of a Wet Towage including: • Maximum Allowable Roll Angle - 6 degrees • Maximum Allowed Pitch Angle - 6 degrees • Maximum Significant Wave Height - 4. 0 meters

ANALYSIS OF A WET TOWAGE APPROVAL Conclusion Based on these results the wet tow of the MODU from Yangon, Myanmar to Singapore in the month of March is feasible.

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