O
O Oil
OAL  Overall length
OAS  Obstacle Avoidance Sonar 
OASIS Open Access Save-time Information System
OBAs Operational Balancing Agreements
OBC Ocean Bottom Cable
OBM Oil Based Mud
OBS Ocean Bottom Seismometer
OBSROV Observation ROV (remote operated vehicle)
OC Operator Console
OCA Offshore Contractors Association
OCIMF  Oil Companies International Marine Forum
OCMA Oil Companies Materials Association (defunct one, incorporated in EEMUA)
OCS Outer Continental Shelf
OCSLA Outer Continental Shelf Lands Act (USA)
OCSV  Offshore Construction Support Vessel 
OCTG  Oil Country Tubular Goods 
OCU Operational Control Unit
OCWR  Overall Control of Wells and Risers 
OD  Outer Diameter
  Open Drain system
ODA Offshore Development Area
ODME  Oil Discharge and Monitoring Equipment
ODP  Ozone Depletion Potential
  Ocean Drilling Program www.website
ODS  Ozone Depleting Substance
OEAA Offshore Energy Achievments Awards 
OEC  Ormat Energy Converter
  Optional Expedited Certificate
OECD  Organisation for Economic Co-operation and Development
OFAF  cooling with Forced Oil Circulation by Means of Pumps
OFDM  Orthogonal Frequency Division Multiplexing
OFOs Operational Flow Orders
off-sh Off-shore
O&G Oil and Gas. 
OG-MRP Oil & Gas-Maximising Recovery Programme 
OGIP Original Gas In Place
OGP International Association of Oil and Gas Producers
  Onshore Gas Plant 
OGT Operator Guidance Tool
OHM Offshore Hydrocarbons Mapping (UK company) 
OHRA  Obstacle Hybrid Routing Algorithm 
OIAC  Offshore Industry Advisory Committee (UK)
OIM  Offshore Installation Manager
OiW  Oil in Water 
OLD On Line Diagram
OLF Norwegian Oil Industry Association (Oljeindustriens Landsforening
OLS  Organizational Leadership and Supervision 
OLT  On-Line Testing
  Offshore Loading Terminal 
O&M Costs, Operation & Maintenance
OMS  Organisation Mondiale de la Santé www.website
OMSA  Offshore Marine Service Association (USA)
ON Office Network (all data networks not including the ICSS)
ONAF Forced Cooling by Air Impelled by Fans 
ONAN  Self Cooling by Natural Air Flow and Radiation 
OOC  Offshore Operators Committee (USA)
OOL Oil Offloading Line
OOS  Ocean Observing System 
OP Operating Pressure  
Operator Position
OPA (90)  Oil Pollution Act, 1990 (USA) www.website
OPC Operation Process Control
  Ordinary Portland Cement  
OPEC  Organisation of Petroleum Exporting Countries 
OPEX Operational Exercise
OPGW  OPtical Ground Wire 
OPIS Oil Price Information Service  
  Online Procurement Information System  
  Online Product Information System  
OPITO   Offshore Petroleum Industry Training Organisation (UK) www.website
OPPS Over Pressure Protection System 
OPRC International Convention on Oil Pollution Preparedness, Response and Co-operation, 1990  www.website
ORQ  Offshore chain grade (according to API RP 2SK) 
ORMAT  Energie Converter brand www.website
ORV Open Rack Vaporizer 
OS  Operator Sation 
OSC  Operations Support Center 
OSCP  Oil Spill Contingency Plan
OSD Oil Spill Dispersant
Offshore Safety Division
OSHA Occupational Safety and Health Administration (dept. of Labor / USA)  www.website
OSPAR  Oslo and Paris Convention (for the Protection of the Marine Environment of the North East Atlantic)
OSPF Open Shortest Path First
OSPIC Oil Spill Public Information Center
OSRL Oil Spill Response Limited
OSRO Oil Spill Removal Organization (OPA 90) www.website
OSS  Operational Systems and Sub-systems
OSV  Offshore Support Vessel 
OS&Y  Outside Screw spindle and Yoke
OT  Operating Temperature
  Operational Test
OTC Operational Test Certificate
  Offshore Technologies Conference (Houston world event) 
OTDR Optical Time Domain Reflectometer 
OTF  On The Fly 
OTP  Operational Test Procedure 
OTS  Operations Training Simulator
OTU  Optical Termination Unit 
OWC Oil Water Contact
OWS Operator Work Station
OWT Oil Water Treatment