Glossary

ULSEL	Ultra-long-spaced electric log.

ultra-long-spaced electric log	ULSEL. A well log recorded with the use of a modified long normal electrode configuration mounted on a 5,000-foot bridle. The AM spacing can be made 75, 150, 600, or 1,000 feet. Differences between the measured resistivities and anticipated resistivities calculated from conventional resistivity logs indicate nearby resistivity anomalies. Used to define the distance to a salt dome flank. May have important application in locating salt overhangs or casing in nearby well bores.

unconformity	A surface of erosion which separates older sediment from younger sediment. Compare nonconformity.

unconsolidated	Pertains to a rock framework which lacks rigidity. Cohesiveness is lacking because of the absence of cement or other binding means. Compare consolidated.

underpressure :	An expression which has been used commonly to refer to low pressure found in some formations, subnormal pressure. Technically, it should be said that underpressure is that amount of pressure by which normal pore pressure exceeds the pore pressure of an underpressured formation. Pore pressure lower than normal pore pressure can occur in a bed of interest when the water solution filling the pores of the body are in communication with an outcrop at an elevation lower than the water table at the well site. More commonly, underpressure results from prior production from a zone.

unit	The producing venture, covered by several leases owned by different companies, which is operated by one company. See also unit operator.

unit operator	The producing company which is in charge of development and production of an oil or gas field in which several companies have joined together to produce.

up time	See lag time.

U.S. Geological Survey	USGS. The U.S. Geological Survey, an arm of the U.S. Department of the Interior, is the principal federal agency concerned with preparing accurate maps of the physical features of the country and providing scientific information essential to the development of the nation's land, mineral, and water resources. It is recognized as one of the world's foremost research organizations in the earth sciences. It makes maps: Topographic maps, showing accurately the shape of the land surface and the location of natural and man made features – hills, valleys, streams, lakes, highways, trails, buildings, etc. Hydrologic maps, showing the availability and quality of water. Geologic maps, showing the types, ages, and configurations of rock formations that lie at and beneath the earth's surface. A variety of outline maps, mineral-resource maps, geophysical maps, state base maps, and many others. It studies the earth's processes that may be hazardous to man and his works, such as earthquakes, volcanic eruptions, and floods, in an attempt to understand how these processes operate, and hence how their destructive effects may be reduced or prevented. It develops new prospecting techniques that can be used by industry in its continuing search for mineral resources. It studies the natural processes that form deposits of valuable minerals. because knowing why certain kinds of mineral resources are formed in certain locations or in certain kinds of rocks may provide clues that will help to find new mineral resources now hidden beneath the earth's surface. It takes a continuing inventory of the nation's water resources and studies areas that have special water problems. It classifies federally owned lands for mineral and water power potential. It does fundamental research in topography, geology, hydrology, geochemistry, geophysics, and related sciences. It publishes maps and reports to make the results of these investigations available to the public.

USGS	See U.S. Geological Survey.