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ADVISORY COMPUTER SYSTEMS & SOFTWARE STATION KEEPING & RISER MANAGEMENT

Global Maritime Technical Services are the analytical and software design and development division of Global Maritime Holdings and are based in the London Headquarters. Global Maritime has operating companies in Aberdeen, London, Houston and Stavanger. GMTS specialise in writing and using software to help design and operate marine drilling rigs. Core corporate specialities include practical and analytical aspects of mooring, D P & stationkeeping, risers, hydrostatic stability, structures and mathematical/statistical simulation. This presentation has been prepared to show the main features of Gmoor 32 a key program at the core of both our design and advisory systems and used throughout the group as the main mooring tool

The main program in the Gmoor 32 suite is Gmoor 32 Q. The Q denotes that it uses the standard quasi-static approach to mooring modelling. The program (as GMOOR for DOS) was approved by the Norwegian Maritime Directorate in 1985 for such analysis (water depths up to 450 m - 1500 ft). Gmoor 32 D adds line dynamic analysis to Gmoor 32 and can perform analysis to the dynamic requirements of API RP 2 SK and Dn. V POSMOOR. The main difference with Gmoor 32 D is that the line tensions are calculated from a lumped mass model which accounts for the mass and drag on the line and the ensuing potential vibration modes. Gmoor 32 D will be released in February 1998 and has the same interface and appearance as Gmoor 32 Q. All the latest Global Maritime software runs under 32 bit Windows (NT, 95 and 98) and interfaces are designed to adhere to those standards with which most users are already familiar. Similarly the products have extensive Help available with the user manual available on-line.

Gmoor 32 is straightforward to use and, provided users are familiar with mooring systems and Windows, they should be achieving useful results very quickly. Existing GMOOR users will find the transition easy and will notice a number of powerful new features :

This is the main Gmoor 32 Display This section is normally the plan view and includes field details if a field plan was prepared This side shows text summaries of results and user options Riser performance details (needs RISERDYN) Input Weather conditions You can also choose the units displayed and the colour scheme you prefer

This is an example with a field plan showing two pipelines

This shows different user selected colour scheme for vessel and background - you can also specify the colour of intact and broken lines

You may specify case details for identifying output and time labels for plotting (future feature)

You can input wind, waves and current if a custom vessel file (CVF) is available - forces and motions are then calculated automatically

You can adjust the payout or break/repair any mooring line

This can also be done by clicking on a mooring line.

Anchors can be repositioned by dragging and dropping

Integrated Riser Analysis An optional feature of the program is Integrated Riser Analysis and Station Keeping Guidance. A model of the riser is incorporated in the mooring analysis and Gmoor 32 calculates the flexjoint angles and slip joint stroke. If limits are set for the slip joint stroke and flex joint angles then Gmoor 32 will provide guidance on the optimum position of the rig.

Limits are set for the slip joint stroke and flex joint angles. The present position of the rig is used to calculate the actual values for both intact and line failed conditions. The optimum location for the rig is then recommended.

The guidance results can be shown graphically. The green zones show where the rig should be positioned to satisfy the input limits. In this example the rig should be 200 ft north of the wellhead to satisfy all three limits.

You can control the thrusters manually both individually and in joystick mode. A future DP version will also model the control system

You can specify the allowable line tension safety factors for code-checking

You can get GMOOR to calculate the line payout changes to retain the present tension distribution and move the vessel to a new target position

The method of analysis can be chosen - consequence does all analyses for all single failures and prepares a summary table.

On a modern PC the solution scheme is fast and the vessel is displayed in the new offset position.

HEAD-UP display shows mooring, environment and thruster forces

Catenary profiles are available

So are tension-excursion characteristics for each line

And the moorings restoring force curves

Gmoor 32 Q handles all the different line configurations GMOOR does including • Multi-component lines in wire, chain or synthetic • Surface or submerged buoys • Sinkers (clump weights) between components Gmoor 32 Q also adds BATCH analysis which can automate the production of location moorings assessment for insurance or certifying authority approval. It can also be used to predict the sequence of events/vessel performance in future weather sequences (forecasts).

Batch runs are performed for sets of weather data. Each batch run will perform an intact analysis and perform both static and transient single line failure analyses for all legs deployed.

A batch analysis for a typical eight leg spread will generate 136 runs if eight weather directions are analysed. A powerful reporting database is used to filter and summarise batch output.

That concludes this brief presentation of Gmoor 32 capabilities For further details please contact Barry Miller, Nigel Thomas or Neil Walker GLOBAL MARITIME TECHNICAL SERVICES 12 Craven Street, London, WC 2 N 5 PB Telephone 0171 930 6545 Fax 0171 839 4206 email gmoor 32@globalmaritime. com