Glossary

a U-shaped tube. v: to cause fluids to flow in a U-tube without adding an outside force. For example, heavy mud in the drill stem will force light mud in the annulus to flow.

the action of fluids flowing in a U-tube (as heavy mud forcing lighter mud down the drill stem and up the annulus).

a federal department that develops regulations governing transportation. Each mode of transportation has a different administration. The administrations under DOT include the U.S. Coast Guard, the Federal Aviation Administration, the Federal Highway Administration, the Federal Railroad Administration, the National Highway Traffic Safety Administration, the Urban Mass Transportation Administration, the Saint Lawrence Seaway Development Corporation, and the Research and Special Programs Administration. Address: 400 7th Street SW; Washington, DC 20590; 202-366-4000.

a federal agency that was created in 1970 from a variety of existing agencies. The EPA administers air pollution, water pollution, pesticide, solid waste, noise control, drinking water, and toxic substances acts. It also has major research responsibilities. Address: 1200 Pennsylvania Avenue NW; Washington, DC 20460; 202-272-0167.

underbalanced drilling.

underbalanced operations.

uninterruptible electrical power supply.

Underground Injection Control.

Underground Injection Practices Council.

ultralarge crude carrier.

the amount by which a tank or a vessel is short of being full, especially on ships. Ullage in a tank is necessary to allow space for the expansion of the oil in the tank when the temperature increases. Also called outage.

see outage gauge.

the opening in the top of a tanker or barge tank compartment through which ullage measurements and sampling operations are carried out.

a paste that is applied to an ullage rule or dip tape and weight to indicate precisely the level at which the liquid meniscus cuts the graduated portion.

a point marked on the ullage hatch or on an attachment suitably located above or below the ullage hatch and situated at a distance above the bottom of a container greater than the maximum liquid depth in the container. Ullage measurements are taken from this reference point.

a graduated rule attached to a dip tape to facilitate the measurement of ullage.

see outage tape-and-bob procedure.

total anticipated recovery of oil or gas from a well, lease, or pool.

the amount of tension, or tensile stress, applied to a piece of equipment that causes it to fail or continue to deform under a decreasing load.

water deeper than 3,000 feet (914 metres).

of or pertaining to operations in ultra deep water.

an extremely low pressure, usually only 10-10 millimetres of mercury or less.

a super­tanker whose capacity is 500,000 deadweight tons or more. Compare very large crude carrier.

an inspection method primarily used for taking thickness readings of steel structures. High-frequency sound waves are introduced to the metal by a diver-held transducer. The soundwaves travel through the metal and bounce off the back wall. The instrument measures the time it takes to return to the transducer.

corrosion-monitoring devices that transmit ultrasonic waves through production structures to locate discontinuities in metal structure, which indicate corrosion damage.

flowmeter used (1) to measure transit times of an acoustic pressure wave with and against the flow (time-of-flight-type meter) to infer pipeline velocity or (2) to reflect sonic energy from scatterers in fluid back to a receiver (Doppler-type meter) to measure volumetric flow rate.

light waves shorter than the visible blue violet waves of the spectrum. Crude oil, colored distillates, residuum, a few drilling fluid additives, and certain minerals and chemicals fluoresce in the presence of ultraviolet light. These substances, when present in mud, may cause the mud to fluoresce.

a hose bundle that supplies a lifeline, breathing gas, communications, power, and heat as appropriate to the diving mode or conditions. Underwater television camera, etc. cabling can also be carried as a component part of the umbilical.

underwater manifold center.

the arithmetic difference between the indicated demand for crude oil and the total disposition of crude oil.

the difference between gas taken into the distribution system and the known quantities of gas taken out of the system.

in pipeline construction, a road crossing bored without casing. The carrier pipe itself is pushed under the roadbed by the boring machine. To reduce potential damage to the coating, slick boring is frequently used. See slick boring.

see open hole.

the uncertainty of a plane curve. The statistical term for the true value of the variable as stated with a degree of confidence; also referred to as the range of uncertainty of the measurement.

see escheat.

unconformity; used in drilling reports.

1. lack of continuity in deposition between rock strata in contact with one another, corresponding to a gap in the stratigraphic record. 2. the surface of contact between rock beds in which there is a discontinuity in the ages of the rocks. See angular unconformity, disconformity.

a loosely arranged, apparently unstratified section of rock.

a formation containing hydrocarbons that is made up all or mostly all of grains of rock (such as sand) that are not solid, or consolidated.

a sand formation in which individual grains do not adhere to one another. If an unconsolidated sandstone produces oil or gas, it will produce sand as well if not controlled or corrected.

compacted beds of clays and silts that are soft.

see blowout.

a general term that refers to hydrocarbon resources that are produced by enhanced recovery methods or by unconventional methods, such as mining or coal gasification.

of or relating to a condition in which pressure in the wellbore is less than the pressure in the formation.

a well-control choke that is specifically designed for underbalanced drilling. One model is a 3-in., rubber-lined, pressure-balanced choke.

the weight, or density, of a drilling fluid that develops less pressure than the formation to which it is opposite in the borehole. Because the pressure developed by the fluid is less than formation pressure, the fluid is underbalanced-it does not balance, or equal, formation pressure.

to carry on drilling operations with a mud whose density is such that it exerts less pressure on bottom than the pressure in the formation while maintaining a seal (usually with a rotating head) to prevent the well fluids from blowing out under the rig. Drilling under pressure is advantageous in that the rate of penetration is relatively fast; however, the technique requires extreme caution.

see flow drilling.

processes on a drilling rig, a well servicing rig, or a coiled tubing unit that occur when the hydrostatic pressure of the fluid in the drill string or tubing string exerts less pressure than the pressure required to equal or exceed the pressure found in a porous and permeable formation.

the amount by which the actual volume that has passed through the meter is less than the indicated volume registered by a meter. See absolute error.

the lower discharge stream in a cone-shaped centrifuge. It moves downward and leaves by way of the apex.

a bit whose outside diameter is worn to the point at which it is smaller than it was when new. A hole drilled with an undergauge bit is said to be undergauge.

that portion of a borehole drilled with an undergauge bit.

an uncontrolled flow of gas, salt water, or other fluid out of the well­bore and into another formation that the wellbore has penetrated.

a program developed under the safe drinking water act (SDWA) to prevent injection well contamination of underground sources of drinking water. The UIC program divides injection wells into five classes (that range from common septic tanks to hazardous waste injection wells) and establishes specific requirements for construction, casing and cementing, plugging and abandonment, types of substances that can be injected, volume and pressures that can be injected, and mechanical integrity of the well.

a committee of state regulators, Environmental Protection Agency personnel, and industry representatives that works with the EPA in the formulation of new regulations.

fresh water sources located under the surface that are suitable for use as drinking water supplies.

salt domes, depleted gas fields, or other suitable underground formations located in a company’s major market areas into which gas is injected during low-demand summer months and from which it is withdrawn during high-demand winter months. May be 20 to 30 feet (6 to 9 metres) thick and can cover many square miles.

recoverable reserves lost as a result of damage to the reservoir.

to enlarge the wellbore below the casing.

a device used to under-ream. See underream.

the amount by which the indicated volume registered by a meter is less than the actual volume that has passed through the meter. Determined by means of a suitable standard device. Compare overregistration.

a phenomenon that occurs when the polished rod of a sucker rod pump is too short to allow the pump’s plunger to travel the full length of its stroke.

a process where steel is cut using an electric arc, oxygen, and a consumable rod.

this center allows the exploitation of smaller offshore fields. It is connected by pipeline to a platform more than 4 miles (6.4 kilo­metres) away. It collects fluids from the wells and sends them to the platform.

a place where dry hyperbaric welding is conducted at ambient pressure in a dry environment.

type of operating agreement that fixes the sharing of costs and benefits for the life of the unit.

a fractional interest in minerals that, when conveyed, gives the new owner that fractional interest in the described tract. For example, a one-quarter undivided interest in an 80-acre (32-hectare) tract amounts to a one-quarter interest in the entire 80 acres, or 20 net undivided mineral acres (8 hectares). Compare divided interest.

see conventional electric log.

product in which spot samples from top, upper, middle, lower, and outlet agree within the precision of the laboratory tests. Similarly, in pipeline transfers, spot samples taken at 1, 20, 50, 80, and 99 percent of the total volume agree within the precision of the laboratory tests.

the geologic principle that the processes that are at work today on the earth are the same as, or very similar to, the processes that affected the earth in the past. The principle was formulated in 1785 by James Hutton, a Scottish geologist. It became an accepted doctrine with the publication in 1830 of English geologist Charles Lyell’s book Principles of Geology. Also called gradualism. Compare catastrophism.

an electrical system with built-in redundancy that supplies (powers) an entire electronic control system, and provides immediate changeover should one part of the system fail.

a coupling device that allows pipes to be connected without being rotated. The mating surfaces are pulled together by a flanged, threaded collar on the union.

a transistor that utilizes charge carriers of only one polarity, such as a field-effect transistor.

1. a piece or several pieces of equipment performing a complete function (such as a beam pumping unit). 2. the joining of all or substantially all interests in a reservoir or field, rather than a single tract, to provide for development and operation without regard to separate property interests. 3. the area covered by a Unitization Agreement.

a device that combines an internal high-pressure fuel pump, an injector valve, and a spray nozzle, and that is used to inject diesel fuel into an engine’s combustion chamber.

the value of a quantity conventionally accepted as having a numerical value of 1. The unit of measurement of a quantity is fixed in order to make quantitative comparison possible between different values of this same quantity.

the oil company in charge of development and production in an oilfield in which several companies have joined to produce the field. Also called crew chief, rig operator.

a railroading, a train in which all the cars making it up are shipped from the same origin to the same destination. Therefore, the train does not have to be assembled and disassembled at rail yards near the origin and destination. Because unit trains often carry only one commodity, the cars are often all the same type, and, sometimes, identical. Also called a block train.

a federal agency involved in platform design. It also works to solve navigation problems. Address: 441 G Street NW; Washington, DC 20314-1000; 202-761-0660.

an agency of the United States Department of Transportation that establishes regulations for offshore vessels and approves standards for plan approval, construction, operation, and inspection of the hull, machinery, electric systems, industrial systems, and safety and lifesaving equipment of mobile offshore drilling units. The agency conducts rig stability tests, awards the original certification of the rig, and conducts annual inspections. It also establishes manning and personnel licensing requirements and investigates casualties. Address: 2100 Second Street SW; Washington, DC 20593; 202-267-2229; www.uscg.mil.

a series of volumes that is a published compilation of all the laws passed by Congress.

a federal service that oversees commercial fishing investigations, fishing research, fishing statistics, sport fishing, and other areas related to the fishing industry. It also conducts wildlife research, enforces federal statutes and regulations applying to migratory birds, maintains the official list of threatened or endangered species, acquires habitats for threatened or endangered species, operates the national refuge system, manages predator and rodent control work, evaluates the impact of offshore development on fish and wildlife, develops programs to protect fish and wildlife from oil spills, coordinates individual and state efforts to rescue and rehabilitate oiled birds, and administers federal aid programs. Address: 1849 C Street. NW; Washington, DC 20204 1-800-344-WILD.

a federal agency within the Department of the Interior established in 1879 to conduct investigations of the geological structure, mineral resources, and products of the United States. Its activities include assessing onshore and offshore mineral resources; providing information that allows society to mitigate the impact of floods, earthquakes, landslides, volcanoes, and droughts; monitoring the nation’s groundwater and surface water supplies and people’s impact thereon; and providing mapped information on the nation’s landscape and land use. Address: 12201 Sunrise Valley Drive; Reston, VA 20192; 703-648-4000.

the combining of leased tracts on a fieldwide or reservoirwide scale so that many tracts may be treated as one to facilitate operations like secondary recovery. Compare pooling.

the usual units of volume for petroleum measurement are the cubic metre, litre, imperial gallon, U.S. gallon, or the barrel (42 U.S. gallons, or 159 litres).

in mathematics, the number 1; a quantity regarded as 1.

monovalent. See valence.

in an ideal gas, a number equal to the pressure of the gas times its molar volume divided by its temperature. See molar volume, mole.

see drilling and delay rental clause.

two tables for use with saturation excursion diving which limit upward and downward excursions, and provide a zone in which the diver can move freely without regard to the number of excursions or their duration without incurring a decompression penalty.

see circulation valve.

in well control, a well in which drilling fluid and formation fluids are erupting from the well. Also see unloading a well.

removing fluid from the tubing in a well, often by means of a swab, to lower the bottomhole pressure in the wellbore at the perforations and induce the well to flow.

a special circulation valve that provides a way of equalizing tubing and annulus pressure. See circulation valve.

a wildcat area.

a classification for offshore rigs that indicates that the rig is constructed so that it can operate safely in offshore waters anywhere in the world.

a straight-chain compound of hydrogen and carbon whose total combining power has not yet been reached and to which other atoms or radicals can be added.

an occurrence or happening for which no one is prepared; an unexpected incident.

a device that slows down the voice of a diver by using helium as part of the breathing mixture.

quicklime.

in process control, an unde­sirable oscillation or variation of a system’s output at its final control element.

a large volume of air (an air mass) that is unsteady and has irregular motion. This instability can cause storms to form in the mass if enough moisture is also present.

a condition in which an offshore floating rig continues to incline after an external force caused an initial small angle.

a fluid that occurs when a foam drilling fluid breaks into its components-that is, it is no longer gas emulsified in a liquid. Instead, it becomes separate drops of liquid in an airflow, or mist. Unstable foam cannot lift cuttings from the hole as well as foam. See mist drilling.

higher on the formation dip angle than a particular point.

a well located high on the structure.

a valve installed above the kelly that can be closed manually to protect the rotary hose from high pressure that may exist in the drill stem. See kelly cock.

the upper value of calibration of a process transmitter where its lower value is the lower range value (LRV).

in tank sampling, a spot sample taken at the mid-point of the upper third of the tank contents, that is, at one-sixth of the depth of liquid below the top surface.

any part of the drill stem, tubing string, or casing string that lies in the upper part of the borehole.

a category of oil production for purposes of price control. Upper tier refers to oil that comes from reservoirs that began producing subsequent to 1972. It also refers to oil produced from wells having a production rate of 10 barrels (1,590 litres) per day or less for a continuous period of 12 months. Also called stripper oil.

the part of the earth’s atmosphere that generally starts at an altitude of 18,000 to 19,000 feet (about 5.5 to 5.8 kilometres) and extends to about 50,000 feet (about 15 kilometres).

thickness forged to the end of a tubular (such as drill pipe) to give the end extra strength. v: to forge the ends of tubular products, such as drill pipe, so that the pipe wall acquires extra thickness and strength near the end. Upsetting is usually performed to strengthen the pipe so that threads, or threaded pieces, such as tool joints, can be added to the pipe.

tubing that is made with a thicker wall and larger outside diameter on both ends of a joint to compensate for cutting the threads.

the point in a line or system situated opposite the direction of flow. adv: in the direction opposite the flow in a line.

an oil company or a part of an oil company that explores for, drills for, and produces oil and natural gas. Also known as exploration and production (E&P) unit.

a market for selling gas or petroleum before it is processed or refined. Compare downstream market.

toward the upper portion of an updip formation.

a soluble, weakly basic, nitrogenous compound, CO (NH2)2, that is used in the manufacture of resins and plastics.

upper range value.

United States Coast Guard.

underground sources of drinking water.

periodic equipment inspections to determine corrosion damage in fields that have been producing for several years.

in diesel engine fuel tanks, that part of the tank’s capacity from which the fuel system can take fuel. Useful volume is less than the actual or total volume of the tank. Compare total volume.

United States Fish and Wildlife Service.

United States Geological Survey.

ultrasonic.

a ratio of the maximum demand of a system or part of a system to the rated capacity of the system or part of the system under consideration.

underwater welding habitat.