| Octane Number |
| A term (Motor Octane Number) devised by Graham Edgar in 1926 to measure the anti-knock quality of gasoline. The octane number of a given fuel is the percentage of iso-octane (octane number: 100) in a blend with n-heptane (octane number: 0) with the same anti-knock properties as a sample of the motor gasoline being tested. A high octane fuel has better anti-knock properties than one with a low number. A similar but improved method (Research Octane Number) was developed in the late 1930's. |
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| Off-Peak Power |
| Electricity used in periods of low demand. |
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| Offshore Platform |
| A fixed structure from which wells are drilled offhsore for the production of crude oil and natural gas. |
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| Oil In Place |
| An estimated measure of the total amount of oil contained in a reservoir (a higher figure than the estimated recoverable reserve of oil.) |
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| Oil Shale |
| A fine-grained, sedimentary rock that contains a solid substance, kerogen, which is partially formed oil. Kerogen can be extracted in the form of shale oil by heating the shale. |
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| Oilsands |
| Deposits of sands and clay (excluding oil shale) heavily impregnated with semi-solid bitumen. Also called tar sands. |
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| Olefin |
| A class of unsaturated aliphatic hydrocarbons of the general formula CnH2n and characterized by relatively great chemical activity. Ethylene, propylene and butenes are typical examples. |
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| OPEC |
| The Organization of Petroleum Exporting Countries, an international oil cartel; its members are Algeria, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, United Arab Emirates, and Venezuela. |
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| Operating Revenue |
| Sales and other operating revenues, excluding excise and sales taxes. Shows how much revenue a company is generating from its main operations, since it does not include other sources of revenue such as equity income or gains on sales of assets. |
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| Operator |
| The company that has legal authority to drill wells and undertake the
production of hydrocarbons that are found. The Operator is often part
of a consortium and acts on behalf of this consortium. |
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| Outage |
| The state of any electrical circuit component when it is not available to perform its intended function because of some event associated with that component. An outage may or may not cause an interruption of service to consumers, depending on the layout of the system. |
