Technical
Thesaurus oil & gas
O
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.