Glossary of Oil Industry Terms

Acidise	injecting acid solution down a well to dissolve carbonate rocks in a reservoir and improve the flow of hydrocarbons to the well.
Acoustic Log	a measurement of the velocities of sound waves imparted to a formation in a well and used mainly for determination of rock porosity.
Acreage	pertaining to an area of ground covered by a company’s exploration permits.
Annulus	annular space between drill string and casing or borehole.
Anomaly	a divergence from the background levels of physical or chemical properties of an area under survey.
Anticline	an upfold in rock strata producing an arch or dome structure that closes in four directions. One of the most common hydrocarbon traps.
Anticlinal Trap	an Anticline that contains a top seal and a reservoir under the top seal.
API	American Petroleum Institute. API gravity is a standard method of measuring density of crude oils and is expressed in degrees.
Appraisal Well or Appraisal Drilling	a well that is being drilled into a discovered hydrocarbon accumulation to further understand the extent and size of the accumulation – usually denoted by “name-2”, “name-3” etc. appraisal wells can be drilled either before or after an accumulation has been developed. an appraisal well usually has a chance of success greater than an exploration well but less than a development well.
A$	Australian dollars.
Barrel or BBL or bbl	an oil field unit of volume. One barrel at standard conditions equals 158.9 litres.
Barite	a sulphate of barium used to add weight to drilling fluids.
Basin	a dip in the earth’s crust usually filled or being filled with sediment. It is a basic concept in petroleum geology.
Bscf or Bcf (gas volume)	billions of standard cubic feet of gas. Equivalent to 1,000,000,000 standard cubic feet (nine zeros)
Bentonite	a type of clay often added to drilling fluid because of its swelling properties when added to water.
Bit	the Bit is the part of the drilling equipment that cuts the rock in order to drill a hole.
Blowout	when downhole pressure overcomes the weight of drilling fluid and rises in a well to the surface out> of control. An underground blowout is where the> overpressuring enters another formation higher in the well, but before it reaches the surface.
Blowout Preventer	a system of valves and rams set in a well which can be closed successively around drill pipe or tubing orinto an open hole to counteract the uncontrolled rise of oil or gas from a reservoir below.
Bopd	barrels of oil per day.
Borehole	the wellbore itself, including the open hole or uncased portion of the well. Borehole may refer to the inside diameter of the wellbore wall, the rock face that the bounds the drilled hole.
Bright Spot	a point on a seismic profile which shows up brighter than surrounding traces because of an increase in amplitude of seismic waves passing from hydrocarbons to water within the pores of a rock.
Caliper Logg	a measurement of the diameter of a well.
Cap Rock	an impermeable layer of rock that traps or halts the upward movement of oil and gas, forming the top or cap of a reservoir.
Carbonates	sedimentary rocks composed of calcium and/or magnesium carbonate e.g. limestone.
Carboniferous	a geological time period approximately 354 to 298 million years ago.
Cash	cash in bank accounts, term deposits and bank discounted bills of exchange that are held by the company. The most liquid of assets.
Casing	steel pipe screwed together to line the inside of a well bore and cemented into place.
Casing Shoe	a heavy section steel tube fitted to the lower end of a casing string to protect the end of the string from damage when running into a well.
Cement Bond Log	a measurement of the strength and bonding of cement to the casing in a well.
Choke	a valve or valves used to control the flow of hydrocarbons from a well by changing the diameter of the orifice.
Christmas Tree	the system of valves and controls placed at the wellhead.
City Gate	the point at which high pressure pipelines deliver gas to low pressure pipelines for distribution to individual users.
Claystone	a sedimentary rock composed predominantly of particles less than silt size usually comprising clay minerals.
Closure	a term used to indicate that a trap exists in the subsurface and there are no avenues for hydrocarbons (if present) to escape.
Completion	the final preparations to ready a well for production. Usually pertains to the tubing and wellhead.
Condensate	hydrocarbons which are gaseous in a reservoir, but which condense to form a liquid as they rise to the surface where the pressure is much less.
Conductor	the first casing string in a well.
Coring	an operation whereby a sample of rock being drilled is allowed to pass through the centre of a special bit and be collected in a core barrel mounted directly behind it.
Cretaceous	a geological time period approximately 141 to 65 million years ago.
Crown Block	an assembly of sheaves at the top of the drilling derrick of a rig over which the hoist lines are passed.
Crude Oil	a generic term for the oil
Culmination	the highest point on a four-way dip closed structure, also used to indicate that a four-way dip closure exists.
Cuttings	rock chips from action of drill bit transported to surface in drilling mud.
CY08 etc	calendar year 2008. From 1 January to 31 December.
Darcy	the unit of measurement of permeability of rock
Delineation Well	(see appraisal well)
Depletion	reduction in petroleum reserves by production.
Depocentre	an area or site of maximum deposition in a sedimentary basin.
Deposition	the laying down of potential rock forming material i.e. sediments.
Depression	a low place of any size on the Earth’s surface, also may refer to a sedimentary trough or basin.
Development Phase	the phase in which a proven oil or gas field is brought into production by drilling production wells.
Development Well or	a well that is being drilled into a reasonably well
Development Drilling	defined hydrocarbon accumulation, - usually denoted by “name-2”, “name-3” etc. development wells are usually planned to exploit an accumulation of known hydrocarbons. The well usually has a chance of success greater than an Appraisal Well. It is usually expected that after drilling a Development Well it will be converted into a Production Well. as nothing is certain in oil field drilling, usually all Development Wells may also be termed Appraisal/Development Wells.
Diamond Bit	a drill bit with impregnated diamonds as the cutting edge.
Dip	the angle of the plan of a bed relative to the horizontal.
Dipmeter	an instrument lowered down the well to measure the dip of the drilled formations relative to the well.
Directional Drilling	intentional deviation of a well from the vertical.
Downtime	the time an operation is postponed, usually due to bad weather or mechanical failure.
Draw-works	the hoisting winch for handling drill pipe and casing on a rig.
Drill Pipe	steel pipe screwed together and used to carry and rotate the drilling tools in a well and to permit the circulation of drilling fluid.
Drilling Fluid	(see mud).
Drillstem Test	a valved test tool is lowered down a well on the end of the drill string to a specific reservoir formation and the valve opened to admit formation fluids.
Drill String	the column of drill pipe lengths screwed together.
Dry Hole	a well drilled without finding oil or gas in commercial quantities.
EBITDAX	earnings before interest, tax, depreciation, amortization and exploration. EBITDAX is an indicator of the raw earning power of the company – essentially net production revenue minus corporate costs.
Electric Logs	measure of the resistivity of rock formations down a well which leads to determination of the rock types.
Ethane	a component of natural gas and the basic feedstock for petrochemical industries.
Exploration Permit	this is the legal instrument that allows an oil> company to hold tenure or title to an area of ground and to explore for hydrocarbons. Cooper Energy holds Exploration Permits in Tunisia and Australia (see PELXXX). Once a commercial discovery has been made a portion of the Exploration Permit will usually be exercised from the Exploration Permit and converted to a production area.
Exploration Well or	a well that is being drilled into a Prospect – usually
Exploration Drilling	denoted by “name-1”
Facies/Lithofacies	the rock record of any sedimentary environment, including both physical and organic characters.
Farm-in/out	an arrangement between one or more parties and the company or group holding a lease title to an exploration or production area whereby the former pays to earn an interest in the permit. Payment may be in cash or in the form of a work program.
Fault	a break or fracture in the earth’s sub-strata where one side of the break moves relative to the other.
Fault Trap	a hydrocarbon trap which relies on the termination of a reservoir against a seal due to fault displacement.
Field	a geographical area under which an oil or gas reservoir lies.
Fishing	to retrieve equipment which has fallen into or is caught in the well.
Flaring	the practice of burning off waste gas or oil during a test or production cycle.
Flow-line or Pipe-line	a cylindrical fibreglass or steel pipe used to transport oil or gas to a sales point. Usually a flowline goes from a well head to the facilities and a flow-line or pipe-line from the facilities to the sales point. The terms flow-line and pipe-line can be used interchangeably but a pipe-line is usually considered more substantial in size than a flowline.
Fluorescence	the luminescence shown when irradiated by ultraviolet light.
Fold/Folding	a bend in strata, commonly a product of deformation.
Formation	a group of rocks of the same age, extending over a substantial area of a basin.
Four-way dip	a structural feature seen on orthogonal seismic lines to dip away in all four possible directions, closure indicating that any hydrocarbons beneath a sealing stratum will be trapped in this feature.
Fraccing	a process used to improve the permeability of a tight reservoir. A specially blended fluid, charged with propants like sand or aluminium pellets, is pumped down a well at high pressure to force passageways into the rock. The propants keep them open once the pressure is released.
Franking Credits	in its simplest form it is corporation tax that has been paid to the Government of Australia but not yet given as a tax credit to investors via a dividend.
FY08 etc	Financial Year 2008. Cooper Energy’s financial year is from 1 July to 30 June.
Gas in Place (GIP or GIIP)	an estimated measure of the total amount of gas contained in a reservoir and, as such, a higher figure than Recoverable Gas. May also be termed Gas initially in place (GIIP) to describe the volume of gas that exists at initial discovery.
Gas/oil ratio (GOR)	the ratio of gas to oil by volume, measured during a production test.
Gazetted	the advertisement of permits by the government calling for applications for exploration licences.
Generation	the process by which organic matter in a source rock is transformed into hydrocarbons in the subsurface.
Geology	the science relating to the history and development of the earth’s crust.
Geophones	microphones used in seismic surveys to electronically pick up returning shock waves and pass them on to the recording equipment.
Geophysics	The physics of the earth, a hybrid discipline involving a combination of physical and geological principles.
Gross Pay	the total thickness of a reservoir rock, including the impervious layers which do not contain hydrocarbons.
Horizon	a term used in seismic interpretation to identify the signal reflected from a particular layer of rock.
Hydrocarbons	general term for oil, gas, condensate and other petroleum products.
Hydrocarbon Kitchen	the part of a sedimentary basin containing mature petroleum source rocks. General term to denote the place where temperatures and pressures are optimum for the generation of oil or gas.
Hydrocarbon Show	evidence of hydrocarbons in drill cuttings.
Hydrocarbon Value Chain	the simple sequential flow of work activities from New Ventures to Exploration to Appraisal to< Development to Production to Sales. Usually all projects in the oil and gas industry follow this route.
In-situ (in place)	refers to total oil or gas reserves contained in a reservoir in the ground as opposed to those reserves which may be recovered.
Intraformational	existing within a geological formation, for example a single shale bed in an alternating sequence of sand and shale.
Joint Venture	a group of companies or individuals who share the cost and rewards of exploring for and producing oil or gas from a permit.
Jurassic	a geological time period approximately 205 to 141 million years ago.
Kelly	hexagonal or square pipe about 15m long attached to the top of the drill string and turned by the rotary table. It is used to transmit the twisting movement from the rotary machinery to the drill string and thus the bit.
Kelly Bushing	a piece of equipment which fits around the kelly at the point where it passes through the rotary table. It is often used as a datum from which to measure the depth of a well.
Kerogen	the organic matter which is the base for the formation of oil or gas.
Kick	a sudden influx of high pressure into a well, usually experienced while drilling.
Kill	the process of increasing drilling fluid weight to control a potential blowout.
Lacustrine	sediments deposited in a lake environment.
Lead	an immature unpenetrated/undiscovered exploration target.
Leakoff	the magnitude of pressure exerted on a formation that causes fluid to be forced into the formation. The fluid may be flowing into the pore spaces of the rock or into cracks opened and propagated into the formation by the fluid pressure. This term is normally associated with a test to determine the strength of the rock, commonly called a pressure integrity test (PIT) or a leakoff test (LOT). During the test, a real-time plot of injected fluid versus fluid pressure is plotted. The initial stable portion of this plot for most wellbores is a straight line, within the limits of the measurements. The leakoff is the point of permanent deflection from that straight portion. The well designer must then either adjust plans for the well to this leakoff pressure, or if the design is sufficiently conservative, proceed as planned.
Licence	an authority to explore for or to produce for oil or gas in a particular area issued to a company by the governing state.
Limestone	a rock composed of calcium carbonate.
Liner	steel tube of small diameter extending into a producing reservoir from the bottom of the last string of casing in a well.
Lithology	a study of the rock types in a given region, including descriptions of mineral content.
Log(s)	see well log.
Log Interpretation	technical analysis of the data obtained in well logging leading to quantitative estimates of various rock properties including contained liquids and gases.
Logging Tools	devices lowered down a well to measure various parameters and properties of the formations being drilled.
Marker crude	a commonly traded crude oil in a particular region that is used as a quality standard to price other crudes.
Market Capitalisation	on an undiluted basis defined as the number of issued shares multiplied by the share price – it is a measure of the value of a company. On a fully diluted basis defined as the number of issued shares plus the number of options multiplied by the share price. The option price should ideally be at a price equal or less than the current share price to be included in a fully diluted basis but this is sometimes ignored.
Mature (source)	the condition, caused by pressure, temperature and time, in which organic matter in a potential source rock will be converted to hydrocarbons.
Migration	the movement of oil/gas from a petroleum source rock into and then within a reservoir rock.
MM (oil volume) or mm (gas flow)	an oil field abbreviation for millions.
MMSTB	millions of standard barrels.
MMCFD	millions of cubic feet per day = 28,317 cubic metres per day.
Monkey Board	the small platform high in the derrick of a rig occupied by the derrickman when guiding stands of drill pipe and casing to and from storage racks during drilling operations.
Mud (drilling fluid)	is the suspension of minerals and chemicals in oil or water which forms the well circulatory system.
Mud Logging	this includes routine geological examination of drill cuttings from a well, plus a record of the variations in drilling rate, mud pumping pressure, depths of formation changes and an analysis of the mud for oil and gas traces.
Net Pay	the aggregate thickness of only those parts of the reservoir which contain and produce hydrocarbons.
Nipple	a completion component fabricated as a short section of heavy wall tubular with a machined internal surface that provides a seal area and a locking profile.
Nipple Down	to take apart, disassemble and otherwise prepare to move the rig or blowout preventers. This term is usually reserved for the dismantling of a blow-out preventer stack.
Nipple Up	to put together, connect parts and plumbing, or otherwise make ready for use. This term is usually reserved for the installation of a blow-out preventer stack.
Nuclear Logs	a measurement of gamma rays and thermal neutrons from down hole formations which can be used to determine rock porosity and lithology.
Oil	a mixture of liquid hydrocarbons of different molecular weights.
Oil Field	a geographical area under which an oil reservoir lies.
Oil/Gas Seep	a natural flow of oil and/or gas to the earth’s surface.
Oil in Place (OIP or OIIP)	an estimated measure of the total amount of oil contained in a reservoir and, as such, a higher figure than Recoverable Oil. Oil initially in place (OIIP) pertains to the oil that would be in the reservoir at initial discovery.
On stream	in production.
Open hole	refers to a well which has no casing or which is cased only to the top of the reservoir section.
Operator	the company which organises the exploration and production programs in a permit on behalf of all the interest holders in the permit.
Packer	a device (often rubber) which seals off a section of the well during testing.
Paper Crude	crude oil which is sold on the futures market, but which will not be physically produced for several months or longer.
Pay Zone	a stratum of rock in which oil and/or gas is found, and from which it is produced.
PELXXX	Petroleum Exploration Licence as used in South Australia e.g. PEL92.
P50 (and P90, Menu Expected and P10)	this is a statistical uncertainty abbreviation that results from probabilistic evaluations.P50 is defined as 50% of outcomes are expected to exceed the estimate and 50% of outcomes are expected to be less than the estimate. It is a good middle estimate. mean and expected (same level of measure Just different names) usually lie about the P40- P30 levels in oil field evaluations and are therefore high estimates. P90 and P10 are low and high estimates respectfully. the PXX number defines the uncertainty of the Estimate and has to be accompanied with a maturity indicator to be meaningful. Cooper Energy uses a very simple and transparent maturity versus uncertainty classification system for recoverable hydrocarbons. The definitions associated with this classification can be downloaded from Cooper Energy’s website (www.cooperenergy.com.au)
Permeability	a measure of the capacity of rock or stratum to allow water or other fluids such as oil to pass through it.
Permian	a geological time period approximately 298 to 251 million years ago.
Permit	an area of specified size within a sedimentary basin which is licensed or allocated to a company or companies by the government for the purpose of exploring for and producing oil and gas. In Australia separate licences are issued for exploration and production.
Petroleum	a generic name for hydrocarbons, including crude oil, natural gas liquids, natural gas and their products.
Petroleum System	the established geological conditions which give rise to petroleum accumulations.
Petrophysical	the physical properties of rocks, in this context, as measured by well logs.
Pig	a mechanical device sent through a pipeline to scour the inside walls or to run internal checks on the integrity of the line.
Pipeline	a pipe through which oil, its products, or gas is pumped between two points, either offshore or onshore.
Play	a specific combination of geological features which is perceived as having potential for petroleum accumulation.
Plug	a seal deliberately placed in a well to prevent escape of high pressure material from the substance after it has been abandoned. Usually plugs are of cement.
POOH (pull out of hole)	to remove the drill string from the wellbore.
Porosity	a measure of the pore space within a rock and expressed as a percentage of volume.
PPLXXX	petroleum production licence as used in South Australia e.g. PPL207. Once a commercial discovery has been made in a PEL the area of the discovery is exercised out of the PEL and converted to a PPL.
Production	the volume of oil that is produced at the facilities. Production should ideally be stated at standard and stabilised conditions but sometimes it can be stated at non-standard or non-stabilised conditions (i.e. the oil has not been fully stabilized and still contains some light hydrocarbon fractions or is at a pressure and temperature that is not standard conditions).
Production Sales	the volume of produced oil that has been sold to the buyer. Usually equal to production minus fuel minus flare minus losses.
Production Well	an exploration, appraisal or development well that has successfully penetrated a hydrocarbon accumulation and has subsequently been prepared so that hydrocarbons can flow to the surface to be processed and sold.
Prospect	a reasonably mature unpenetrated/undiscovered exploration target.
Proven or Proved	an estimate of the future volume of hydrocarbons
Recoverable Oil	that is expected to be economically recovered and sold from the producing oil fields. Cooper Energy usually states Proved volumes at the P50 estimate level (see P50 definition). proved recoverable oil is an estimate of what is accessible in the future by existing infrastructure – assuming no further capital investment. Probable and Possible estimates usually need some level of further investment before the volumes of hydrocarbons can be accessed. Cooper Energy uses a very simple and transparent maturity versus uncertainty classification system for recoverable hydrocarbons. The definitions associated with this classification can be downloaded from Cooper Energy’s website (www.cooperenergy.com.au).
PSC	abbreviation of production sharing contract. This is the title instrument that allows an oil company to hold tenure to an area of ground and defines the work program associated with the area and the contractors rights to any production. PSCs are used in many countries. in Tunisia they allow the oil company to produce hydrocarbons after declaration of a commercial discovery. In Indonesia they allow the oil company to explore for and produce hydrocarbons. Indonesia uses the PSC as the exploration and production instrument rather than issue separate Exploration Permits and production concessions.
Quartz	a mineral composed of silicon dioxide.
Quaternary	the most recent geological era, commencing approximately 1. 8 million years ago.
Ream	to enlarge a wellbore. Reaming may be necessary for several reasons. Perhaps the most common reason for reaming a section of a hole is that the hole was not drilled as large as it should have been at the outset. This can occur when a bit has been worn down from its original size, but might not be discovered until the bit is tripped out of the hole and some undergauge hole has been drilled. Also, some plastic formations may slowly flow into the wellbore over time, requiring the reaming operation to maintain the original hole size.
Recovery Factor	simply the volume of hydrocarbons that is expected to be recovered from a reservoir divided by the original amount of hydrocarbons that was in place at discovery or the start of the recovery process. Usually expressed as a percentage
Recoverable Gas	an estimated measure of the total amount of gas which could be brought to the surface from a given reservoir.
Recoverable Oil	defined as the amount of oil that has been added
Replacement Ratio	to the recoverable oil portfolio through the financial year divided by the amount of production. the ratio will be greater than one if more oil has been added to the portfolio than has been produced – the best result. A ratio greater than zero but less than one means that recoverable oil has been added to the portfolio but it is less than what was produced – an acceptable result. A ratio of zero means no recoverable oil has been added to the portfolio – not a good result. it is possible to go negative if no oil has been discovered during the year and/or if studies revise downwards the previous recoverable oil estimate – the worst result. unless stated otherwise Cooper Energy usually states the ratio in relation to the Proved oil portfolio.
Refinery	an installation that manufactures finished petroleum products from crude oil, unfinished oils, natural gas liquids and other hydrocarbons.
Reservoir	a porous rock or formation which holds hydrocarbons within the pore spaces between individual grains.
Risk	an expression of uncertainty often relating to the presence of principal geological factors controlling oil accumulations.
Rolling Cutter Bit	a bit with hardened steel or tungsten carbide teeth of varying lengths and spacings mounted on three roller cones.
Rotary Drilling	a system whereby a bit is forced against a rock face and mechanically rotated to penetrate the various formations.
Rotary Swivel	the part of a rotary drilling rig which connects the travelling block to the drill string.
Rotary Table	a flat plate in the drill floor which is turned mechanically at varying speeds and imparting the rotary action to the drill string which passes through its centre.
Roughneck	a rig worker who handles the drill pipe and other equipment on the drill floor.
Round Trip	the complete operation of pulling out the drill string from a well (for instance to change a bit) and then running it back into the well.
Roustabout	a general labourer on a rig.
Rugosity	the irregularity or roughness of a borehole, often caused by unstable formation or by poor drilling practice.
Sandstone	a sedimentary rock composed predominantly of sand sized grains, usually quartz.
Sales Revenue	the Production Sales multiplied by the price that is received for each unit of sale i.e. 1 million barrels multiplied by US$100 per barren equals US$100 million of revenue. sales revenue does not have deductions for operating costs or off-take costs.
Seal	an impermeable rock (usually claystone or shale) that prevents the passage of hydrocarbons.
Sediment	solid material, whether mineral or organic, which has been moved from its position of origin and redeposited.
Sedimentary Cycle	the period encompassing an encroachment of the sea over the land and then a subsequent withdrawal of the sea.
Sedimentary Rock	a rock formed as a result of the consolidation of sediments.
Seep	a point where migrating oil or gas, not already trapped, reaches the earth’s surface.
Seismic Survey	a method of determining the sub-surface features by sending shock waves into the various buried rock layers in the earth and measuring the time taken to return to the surface.
Sequence	a succession of sedimentary rocks laid down sequentially.
Shale	a claystone exhibiting a finely laminated structure.
Shale Shaker	equipment near the rig floor which separates the drill cuttings from the drilling mud.
Shoe	(see casing shoe).
Shows	the detectable presence of hydrocarbons observed during the drilling of a well.
Sidetracking	when a well is deliberately deviated around an obstruction or branched off part way down a completed well to reach another part of the reservoir.
Silt/siltstone	rock intermediate in texture and grain size between sandstone and claystone.
Source rock	a sedimentary rock which is capable to generating hydrocarbons under optimum maturation conditions of temperature, pressure and time.
Sour Crude	crude oil that contains appreciable amounts of sulphur compounds.
Spot Market	the sale of individual shipments of crude oil priced at the international market rate at the time of sale.
Spud In	to begin drilling. To start a well. Usually the point in time when the bit penetrates the surface of the earth.
Spud Date	the date when drilling of a well begins.
Stabilised Conditions	the end product that is sold. For oil this is usually minus all the volatile light hydrocarbon fractions.
Stack	a processed seismic record that contains traces that have been added together from different records to reduce noise and improve overall data quality. The number of traces that have been added together during stacking is called the fold.
Standard Conditions	the benchmark pressure and temperature condition for measuring hydrocarbons in the petroleum industry – usually 60 ºF (degrees Fahrenheit) and 14.7 psia (pounds per square inch absolute).
Stratigraphy	a description of the rock formations in sequence from top to bottom in a sedimentary basin.
Structural Trap	a trap formed as a result of folding, faulting or a combination of both.
Structure	in oil industry terms it refers to a feature within the earth’s crust with the potential to trap migrating hydrocarbons.
Sweet Crude	crude oil that is free of sulphur compounds.
Tectonic	descriptive of all movements of the Earth’s crust caused by directed pressures, and the results of those movements.
Tertiary Era	an era of geological time approximately 65 to 1. 8 million years ago.
Test	(see wireline test).
Three Dimensional Seismic Survey (3D)	a survey with seismic lines set out in close grid pattern to gain better resolution of detail in an area.
Tight	a term indicating that a formation has no permeability and hydrocarbons cannot flow in economic or commercial quantities from the rock.
Time Map	a plan of mapped horizons from the seismic sections where the contours connecting equal values in times of waves reaching the geophones are plotted on the grid map for the survey. To convert this to a geological map, velocity measurements are used to change time to depth values.
Toolpusher	the chief driller in charge of operations on the rig floor.
Top Drive	a drilling system where a motor is attached to the top of the drill string in the rig derrick to impart a rotary action directly, rather than use a Kelly and rotary table.
Top seal	an impervious layer of rock which overlies a reservoir rock, thus preventing hydrocarbons from escaping to the surface.
Transmission Cost	the cost of transporting oil or gas to market, usually refers to pipeline transport and includes a fee for the pipeline owner.
Transmission Lines	usually refers to high pressure pipelines carrying natural gas from the producing areas to major markets.
Trap	a formation in the earth’s sub-surface which prevents the onward migration of hydrocarbons.
Trend	a strike direction of a geological feature.
Triassic	a geological time period approximately 251 to 205 million years ago.
Tri-cone it	(see rolling cutter bit).
Tscf or Tcf (gas volume)	trillions of standard cubic feet of gas. Equivalent to 1,000,000,000,000 standard cubic feet (twelve zeros)
Tubing	usually a continuous steel pipe that is run from the wellhead to the reservoir to transport hydrocarbons from the reservoir to the surface. usually part of the Completion.
Turbo Drill	a drill bit which is rotated via a multi-stage turbine mounted at the bottom of the drill pipe. Power to rotate is supplied by the drilling fluid being pumped down hole from the surface.
Unconformity	lack of parallelism between rock strata in sequential contact, caused by a time break in sedimentation.
Updip	the direction leading most directly to higher elevations on an inclined stratum or structure.
Unloading Station	when oil is trucked the Unloading Station is the destination point where oil is pumped out of the truck. trucks are filled up at the Loading Station at the oil facilities before driving off to the Unloading Station.
Uplift	elevation of any extensive part of the Earth’s surface relative to some other part.
US$	united states dollars.
Vibroseis	a form of survey where the seismic waves are created by mechanically vibrating a steel pad or plate on the earth’s surface.
Wash	a term used to describe loose debris.
Wellbore	(see borehole).
Well-log (log)	a recording of rock properties obtained by lowering various electrical or nuclear instruments down a drilled well.
Wellhead price	the price at which petroleum producers sell oil or gas from the field.
Wildcat	the first well drilled in a new area. It can also mean the first well in a new structure or prospect.
Wireline test	a test for hydrocarbons in a formation by lowering a chamber downhole on the end of a wire and allowing reservoir fluids to flow into it.
Working Capital	current Assets minus Current Liabilities.
Workover	the re-entry into a completed well for modification or repair and maintenance work.