At its core, a MODU mooring study is simply the development of a mooring design based on assumptions and possibilities. It involves engineering, design work, and the execution of analyses to validate the design. The mooring study can examine one or more of the following items at the client’s request:
- Rig selection (size, type, DP assisted, riser motions, etc.);
- Field arrangements (pipeline routing, drill center layout, etc.);
- Mooring component requirements (chain, wire, polyester, buoys, anchor type, etc.)
- Installation vessel selection (size, capabilities, etc.);
The variables that must be considered for MODU mooring studies depend on the goal.
- One goal may be to help the client select drilling rigs that facilitate a more efficient or cost effective mooring program for a given location and / or water depth.
- Another goal may be to provide information about the pipeline routing’s effect on the MODU mooring layouts, equipment choices, and installability.
The cost and reliability of the mooring system are matters that should not be neglected and mooring studies can provide technical and commercial information that operators can use to plan efficient and cost effective drilling campaigns.
In order to perform a mooring study, some basic information is required and it varies based on the client’s goals.
- If the client has shortlisted a few drilling rigs to choose from, then mooring systems can be designed for each rig at the proposed location. For this type of study, in addition to the drilling rig information, an understanding of the metocean data and bottom features (subsea infrastructure, bathymetry, soil conditions, etc.) is necessary. Knowledge of the site specific information and developing preliminary designs for the shortlisted rigs allows the designer to highlight the differences between each rig and mooring system at the location of interest.
- If the goal is to optimize pipeline routing, then routing variations may be considered and MODU mooring systems can be designed for each option. Considering MODU mooring systems when selecting pipeline routings can be beneficial, as the mooring engineer and the client can work together to reduce the need for specialized equipment which could end up being costly or difficult to source.
The benefit of conducting MODU mooring studies is that they enable optimization of the drilling campaign from a project standpoint. The client can properly account for drilling rig costs, station keeping costs, and variations in efficiency in their decision making. The end results should be safe and reliable mooring systems that are the most cost effective during drilling operations and on the front and back end of a drilling campaign when the rig is moving on or off location.