Technical
Thesaurus oil & gas
Letter
U
Ullage
The quantity a container requires
to completely fill it, i.e., the space in the container remaining above the
liquid level.
Ultra slim hole drilling
The application of mineral
drilling concepts and techniques for the purpose of low cost petroleum exploration.
See slim hole drilling.
Ultra-large crude carrier (ULCC)
An extremely large ocean-going
tanker of over 300,000 metric tonnes deadweight used to transport crude oil
from its source to a transhipment storage facility or direct to a refinery.
Unconformity
A tectonic feature in which
strata are eroded and subsequently overlaid with younger strata (sometimes
angular), which are said to lie unconformably on the older strata; the actual
boundary between the two sets of strata.
Unconformity trap
A trap in which the escape
of hydrocarbons is prevented by impervious rocks unconformably overlaying
the reservoir. See unconformity.
Underwater acoustics
A special field of technical
acoustics dealing with the physics of sound propagation in the water.
Underwater position fixing
A method of position fixing
for surface vessels, submersibles or towed devices in relation to a network
of underwater acoustic beacons on the sea-bed with known relative positions.
Unit operator
The oil company in charge
of development and producing in an oil field in which several companies have
joined together to produce the field.
Unitisation
When owners of oil and/or
gas reserves pool their individual interests in return for an interest in
the overall unit, which is then operated by a single company on behalf of
the group, thus increasing efficiency.
Universal time (UT)
Time as defined by the rotational
motion of the Earth and determined from the apparent diurnal motions which
reflect this rotation. Because of variations in the rate of rotation, universal
time is not rigorously uniform. Also called Greenwich Mean Time.
Unsaturated hydrocarbon
A hydrocarbon (such as ethene
or ethyne) containing one or more double or triple carbon-to-carbon bonds
in its molecule.
Up dip
Proceeding or lying upwards
in the direction of inclination of strata to the horizontal. The opposite
of down dip.
Uplift
The amount of oil that can
be recovered from a field annually before taxes have to be paid.
Upstream
A term referring to industry
operations before the refinery and marketing operations, i.e. production,
handling and transport.
UTM
Universal Transverse Mercator:
this projection is the most common surveying and mapping grid projection.
It is a system of cartesian coordinates that have been predetermined to reference
points on the Earth's surface. In this instance,