Technical Thesaurus
oil & gas
Letter
OAPEC
The Organisation of Arab Petroleum Exporting
Countries. This grouping includes the Arab members of OPEC as well as certain
other minor Arab oil producers such as
Obligatory wells
Exploration wells that an operator undertakes to drill
in a given area as a condition for being allocated an exploration licence.
Observation well
This is a special well drilled to allow observation of
fluid levels, changes in pressure etc. within the reservoir as production
proceeds.
Observation/s (tidal)
A series of measurements taken in order to provide the
information required for the reduction of sounding, and the data for tidal
prediction and investigation.
Oceanographic
Concerning the chemical/physical parameters of the sea
(e.g. tides, currents and salinity).
Octane
The saturated hydrocarbon (alkane) with eight carbon
atoms in its molecule (C8H 18); the eighth member of the paraffin series -a
liquid under normal conditions.
Octane number
A measure of the resistance of a fuel to pre-ignition
("knock") when burned in an internal combustion engine.
Odorant
A substance such as mercaptan that is added to natural
gas and natural gas liquids when used as fuel {which are normally odourless) to
give them a characteristic smell and thus enable them to be detected.
OECD
Organization of Economic Cooperation and Development
Offshore
The adjective applied to any structure of activity
located or carried out at sea as opposed to on land {onshore).
Offshore drilling
Drilling for oil in an ocean, gulf, or sea, usually on
the continental shelf. A drilling unit for offshore operations may be a mobile
floating vessel with a ship or barge hull, a semi-submersible or submersible
base, a self propelled or towed structure used as a production platform when
drilling is completed. In general, wildcat wells are drilled from mobile
floating vessels (as semi-submersible rigs and drillships) or from jack-ups,
while development wells are drilled from platforms. See drillship, jack-up
drilling rig, platform, semi-submersible drilling rig, and wildcat.
Offtake pattern
Schedule(or pattern) specifying the desired rate of
hydrocarbon withdrawal from the different wells/reservoirs/platforms to meet
sales or other forecasts.
Oil
A mixture of liquid hydrocarbons of different
molecular weights.
Oil trap
Geological structure of any type which traps migrating
hydrocarbons, thereby causing an oil field to form.
Oil field
A geographical area under which an oil reservoir lies.
Oil gasification
The manufacture of gas from oil for use as a fuel.
Oil in place
An estimated measure of the total amount of oil
contained in a reservoir, and, as such, a higher figure than the estimated
recoverable reserves of oil.
Oil lubricating
Oil used for lubrication. Also called lube oil or
lubricant.
Oil pipeline
Pump crude or refined oil between two places, either
offshore or onshore.
Oil sand
Oil shale
Rocks of sedimentary origin from which liquid oil can
only be extracted through crushing and distillation to destruction in a high
temperature retort. (Oil shale is abundantly available in several areas of the
world, but its economic extraction has almost always remained tantalisingly
just out of reach).
Oil slick
A layer of oil floating on the surface of the sea,
generally caused by some sort of accident or spillage, but which is
occasionally caused by natural seepage from the ocean floor.
Oil trap
Geological structure of any type which traps migrating
hydrocarbons, thereby causing an oil field to form.
Oil zone
A formation or horizon of a well from which oil may be
produced. The oil zone is usually immediately under the gas zone and on top of
the water zone if all three fluids are present and segregated.
Oil/water contact (OWC)
That level in reservoir rock above which oil is
produced rather than water, and below which water is produced.
Olefin
See alkene.
Onshore
The adjective applied to any structure or activity
located or carried out on land as opposed to at sea (offshore).
Opaque
Opposite of 'transparent'; used to denote an oil price
which is not publicly and incontrovertibly available to observers, particularly
in the case of netback contracts, barter and countertrade where contract terms
may be expressed in non-monetary terms.
OPEC
The Organisation of the Petroleum Exporting Countries.
Formed in 1960, OPEC's original objectives were to coordinate and promote the
interests of the larger petroleum exporting countries and its foundation
stemmed from dissatisfaction over the price fixing arrangements with oil
producing companies. In the 70s, OPEC countries controlled some 70 per cent of
their output, they contributed more than 50 per cent of world output and
accounted for 80 per cent of the oil used by importing countries.
Open
1. Of a well bore, having no casing. 2. Of a hole,
having no drill pipe or tubing suspended in it.
Open hole:
1. Any well bore in which casing has not been set. 2.
Open or cased hole in which no drill pipe or tubing is suspended.
Operator
An individual, partnership or corporation that has
legal authority to drill wells and undertake production if hydrocarbons are
found; the operator may either drill the wells himself or employ a drilling
contractor for this purpose. The operator is often part of a consortium and
acts on behalf of this consortium.
OPITO
The Offshore Petroleum Industry Training Organisation.
An independent body in the
Optimum
The best or most favourable.
Option
The right to obtain, within a certain period of time,
other rights; e.g. a company that has the right to acquire exploration rights
in a particular block is said to have an option there on.
Orifice
A device to restrict partially the flow through a
pipe; the difference in pressure on the two sides of the orifice plate can be
used to measure the flow rate through the pipe.
Orifice meter
A flow rate measuring device on a pipeline that
measures the pressures upstream and downstream of a restricting orifice placed
in the line enabling the volume to be calculated
Orifice plate
A disc with a restricting orifice in it, placed in a
flow stream to measure the rate of flow through a pipe. From the pressures
measured upstream of the plate the rate of flow can be calculated.
Origin
In surveying, the reference position from which angles
or distances are reckoned. See also coordinates (origin of).
Orthoxylene
An aromatic compound used in the manufacture of
phthalic anhydride which, in turn, is used mainly in producing dyes.
Outstep well
See step out well.
Overshot
A fishing tool for recovering lost drill pipe or
casing. See fishing tool.
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