Mobile offshore drilling unit (MODU) means a vessel capable of engaging in drilling operations for the exploration for or exploitation of resources beneath the sea-bed such as liquid or gaseous hydrocarbons, sulphur or salt. (SOLAS IX/1, MODU Code 2009 paragraph 1.3.40).
In other we can understand this as:
The term ‘unit’ as used herein is intended to mean any mobile offshore structure or vessel, whether designed for operation afloat or supported by the sea bed, built in accordance with the Requirements and classed by a member Society, and includes the entire structure and components covered by the Requirements.
The term ‘drilling unit’ as used herein means any unit intended for use in offshore drilling operations for the exploration or exploitation of the subsea resources. The term ‘self-propelled unit’ as used herein refers to a unit which is designed for unassisted passage. All other units are considered as non self- propelled.
The term ‘Requirements’ as used herein refers to the ‘International Association of Classification Societies’ requirements concerning mobile offshore drilling units and other similar units
Types of drilling units
- Self-elevating drilling units.
- Column stabilized drilling units.
- Surface type drilling units.
Other types of drilling units
Units which are designed as mobile offshore drilling units and which do not fall into the above mentioned categories will be treated on an individual basis and be assigned an appropriate classification designation.