crater v: (slang) to cave in; to fail. After a violent blowout, the force of the fluids escaping from the wellbore sometimes blows a large hole in the ground. In this case, the well is said to have cratered. Equipment craters when it fails.
crawler n: a self-propelled X-ray machine that rides inside pipe to examine welds for possible defects.
CRC abbr: Coordinating Research Council, Inc.
crd abbr: cored; used in drilling reports.
creaming or emulsiom n: the settling or rising of the particles of the dispersed phase of an emulsion. Identifiable by a difference in colour shading of the layers formed.
Creaming can be either upward or down- ward, depending on the relative densities of the continuous and dispersed phases.
created fracture n: fracture induced by means of hydraulic or mechanical pressure exerted on the formation. crest n: the top of a wave.
Cretaceous ad}: of or relating to the geologic period from about 135 million to 65 million years ago at the end of the Mesozoic era, or to the rocks formed during this period, including the extensive chalk deposits for which it was named.
crew n: 1. the workers on a drilling or workover rig, including the driller, the derrickhand, and the rotary helpers. 2. any group of oilfield workers.
crew chief n: the driller or head well puller in charge of operations on a well servicing rig that is used to pull sucker rods or tubing.
crg abbr: coring; used in drilling reports.
criminal penalties n pi: penalties (fines or imprisonment) for damages against society or government, typically determined by court cases brought against individuals or corporations.
criteria pollutants n pi: the six air pollutants listed under NAAQS in the CAA: ozone, carbon monoxide, sulfur dioxide,lead.
nitrogen dioxide, and particulate matter.
Sometimes called conventional pollutants.
critical density n: the density of a substance at the critical temperature and pressure.
critical flow n: the rate of flow of a fluid that is equivalent to the speed of sound in that fluid.
critical-flow prover n: a pipe-shaped device with a restriction, usually an orifice or nozzle, that is used to measure the velocity of gas flow during an open-flow test of a gas well.
critical point n: 1. the point at which, in terms of temperature and pressure, a fluid cannot be distinguished as being either a gas or a liquid, i.e., the point at which die physical properties of a liquid and a gas are identical.
2. one of the places along die length of milling line at which strain is exerted as pipe is run into or pulled out of the hole.
critical pressure n: the pressure needed to condense a vapour at its critical temperature.
critical speed n: the speed reached by an engine or rotating system that corresponds to a resonant frequency of the engine or system. Often, in combination with power impulses, critical speed can cause damaging shock waves.
critical temperature n: the highest temperature at which a substance can be separated into two fluid phases-liquid and vapour. Above the critical temperature, a gas cannot be liquefied by pressure alone.
critical value n: see critical point, defn. 1.
critical velocity n: the velocity at the transitional point between laminar and turbulent fluid flow. See laminar flow, turbulent fluid flow. critical volume n: the specific volume of gas at its critical temperature and pressure.
critical weight n: weight placed on the bit that results in tension on the drill string, which causes the mill string to vibrate at tile rotary speed being used. A drill stem operating with critical weight and at the critical speed for that weight will have stresses develop that cause very rapid failure.
critical zone n: in tanks with floating roofs, the vertical range in which the gauging measurements are not accurate.
crooked bole n: a wellbore that has been unintentionally drilled in a direction other than vertical. It usually occurs where there is a section of alliterating hard and soft strata steeply inclined from the horizontal.
crooked bole country n: an area in which particular subsurface formations make it difficult to keep a drilled hole straight.
cross assignment n: when several producers, either voluntarily or by state regulation, pool acreages to form a "unit."
They may cross-assign their leases to one another, creating a common obligation to each royalty owner.
cross-bedding n: sedimentation in which laminations are transverse to the main stratification planes.
crosshead n: the block in a mud pump that is guided to move in a straight line and serves as a connection between the pony rod and the Commenting rod.
cross linking n: a process of molecular bridging of polymers with other chemical substances that alters viscosity and shear rates to enhance lifting of bit cuttings and increase drilling rates.
crossover n: the place at each end of the drawworks drum where the drilling line being spooled onto or off of the drum stops moving in one direction and starts moving in the other direction. Also called turn back.
crossover joint n: a length of casing with one thread on the field end and a different thread in the coupling, used to make a changeover from one thread to anod1er in a string of casing.
cover packer n: a type of packer developed for a dual-completion well in which there are
both an oil and a gas zone, with the gas zone on the bottom.
crossover section n: see angle-control section.
crossover sub n: a sub that allows different sizes and types of drill pipe to be joined.
cross sea n: the irregular wave patterns produced when different wave systems cross each other at an angle.
cross section n: I. the property of atomic nuclei of having the probability of collision with a neutron. The nucleus of a lighter element is more likely to collide with a neutron than is the nucleus of a heavier element. Cross section varies with the elements and with the energy of the neutron.
2. a geological or geophysical profile of a vertical section of the earth.
cross sectional area n: total area of the wall thickness if the pipe were to be cut transversally.
cross-thread v: to screw together two threaded pieces when the threads of the pieces have not been aligned properly.
crown n: I. the crown block or top of a derrick or mast. 2. the top of a piston. 3. a high spot formed on a tool joint shoulder as the result of wobble.
crown block n: an assembly of sheaves mounted on beams at the top of the derrick or mast and over which the drilling line is reeved. See block, reeve the line. sheave.
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crown frame flanges 47 curtailment
crown frame flanges n pi: projections on the frame to which the crown block is attached.
Crown-O-Matic n: see crown saver:
crown platform n: the working platform at the top of the derrick or mast that permits access to the sheaves of the crown block and provides a safe working area for service to the gin pole. See crown block.
crown saver n: a device mounted near the drawworks drum to keep the driller from inadvertently raising the travelling block into the crown block. A probe senses when too much line has been pulled onto the drum, indicating that the travel block is about to strike the crown. The probe activates a switch that simultaneously disconnects the drawworks from its power source and engages the drawworks brake.
crown walkaround n: the structure at the top of the drilling derrick or mast that supports the crown block. Also called water table.
crow's nest n: an elevated walkway where employees work (as on the top of a derrick or a refinery tower).
crude oil n: unrefined liquid petroleum. It ranges in gravity from 9. API to 55. API and in colour from yellow to black. and may have a paraffin, asphalt, or mixed base. If a crude oil, or crude, contains a sizeable amount of sulphur or sulphur compounds, it is called a sour crude; if it has little or no sulphur, it is called a sweet crude. In addition, crude oils may be referred to as heavy or light according to API gravity, the lighter oils having the higher gravities.
crude oil average domestic first purchase price n: the average price at which all domestic crude oil is purchased. Before February 1976, the price represented an estimate of the average of posted prices;
since then, it represents an average of actual first purchase prices. Frequently called wellhead price.
crude oil refinery input n: total crude oil (including lease condensate input to crude oil distillation units and other processing units.
crude oil stocks n: stocks of crude oil and lease condensate held at refineries, in pipe- lines, at pipeline terminals, and on leases.
crust n: the outer layer of the earth, varying in thickness from 50 to 30 miles (10 to 50 kilometres). It is composed chiefly of oxygen, silicon, and aluminum.
cryogenic plant n: a gas-processing plant that is capable of producing natural gas liquid products, including ethane, at very low operating temperatures.
cryogenics n: the study of the effects of very low temperatures.
crystalline e n: rock texture that is the result of progressive and simultaneous interlocking growth of mineral crystals. Compare clastic texture.
crystallisation n: the formation of crystals from solutions or melts.
Cs abbr: cirrosttatus.
Ctl abbr: the correction for temperature of liquid; a factor used during proving to convert the temperature of a liquid to a standard temperature.
Cts abbr: the correction for temperature of steel; a factor used during proving to adjust the temperature of the prover steel to a standard temperature.
CU abbr: cubic.
Cu abbr: cumulus.
cubic centimetre (cm3) n: a commonly used unit of volume measurement in the metric system equal to 10-6 cubic metre, or I millilitre. The volume of a cube whose edge is 1 centimetre.
cubic foot (ft3) n: the volume of a cube, all edges of which measure I foot. Natural gas in the United States is usually measured in cubic feet. with the most common standard cubic foot being measured at roof and 14.65 pounds per square inch absolute, although base conditions vary from state to state.
cubic metre (m3) n: a unit of volume measurement in the metric system, replacing the previous stagnant unit known as the barrel, which was equivalent to 35 imperial gallons or 42 US gallons. The cubic metre equals approximately 6.2898 barrels.
cumulonimbus n: a cloud formed from a cumulus cloud that has reached great vertical development. This type of cloud has a top composed of ice crystals and a bottom composed of water droplets. Also called a thunderhead.
cumulus n: a white, puffy cloud with a dark base. Its shape is constantly changing.
Prominent in the summer months, cumulus clouds generally cover only 25% of the sky.
cup case thermometer n: a holder for a mercury-in-glass thermometer that incorporates a small metal container into which the bulb of the thermometer is inserted and that serves to hold a small sample of liquid the temperature of which is being measured. The liquid in the cup keeps the bulb sub-merged in liquid until the temperature is recorded.
cup pecker n: a device made up in the drill stem and lowered into the well to allow the casing and blowout presenters to be pressure- tested. The sealing device is cup-shaped and is therefore called a cup.
cup test n: see packer test.
cup-type elements n pi: rubber seals that are energised by pressure and not by mechanical force.
cure v: to age cement under specified conditions of temperature and pressure.
cure a title v: to remedy defects and omissions that, in the opinion of the examining attorney, could make the present owner's claim to property questionable. To cure a title. a title examiner may require additional facts not evident in the material examined. The curative material is usually obtained in recordable form.
current n: 1. the flow of electric charge or the rate of such flow, measured in amperes. 2.
the predominantly horizontal movement of ocean waters.
current meter n: an instrument that records an ocean current's speed and direction (along with temperature, salinity, pressure, and other variables). The current meter is moored in position by an anchor or weight on the ocean bottom that is connected to a float at the surface.
curtailment n: reduction in service or purchases below contracted-for levels.
Curtailment of gas sales service is a method of balancing a utility's natural gas requirements with its natural gas supply.
There is usually a hierarchy of customers for the curtailment plan based on priority of us- age according to established regulatory standards of priority. A customer may be required to cut back partially or totally to eliminate this take of gas, depending on the severity of the shortfall between gas sup- ply and demand and the customer's position in the hierarchy. From the customer's standpoint. curtailment may also mean a reduction by the customer of its takes of gas from its supplier. Curtailment of a transportation service occurs when demands for service exceed the capacity of the pipeline. Capacity curtailment is based on contract rather than end-use priority. All interruptible service must be entirely cur- tailed before any firm service is curtailed.
Currently, interruptible transportation service is curtailed based on position in the first-come, first-served queue. Firm transportation service is usually curtailed on a pro rata basis.
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cushion 48 CZM
cushion n: a quantity of water, drilling fluid, or compressed gas placed inside drill pipe or tubing to control both annular and formation pressures. Usually mud in the pipe or tubing supports prevents the pipe or tubing from collapsing; mud also holds back formation pressure pushing up the pipe or tubing. But sometimes, such as in drill stem testing, it is necessary to have empty pipe or tubing downhole. The cushion protects the pipe or tubing until it is in place. It also allows control of the rising formation pressure as the cushion is removed, as in drill stem testing, to prevent formation damage.
cushion gas n: see blanket gas.
custodian n: also called a lease operator or pumper. See pumper.
custody transfer n: the changing of the ownership of or the responsibility for quantities of gas, petroleum, or petroleum products. See also lease automatic custody transfer:
cut n: 1. portion or fraction of hydrocarbons that have been separated according to boiling point or gravity. 2. the line of demarcation on the measuring scale made by the material being measured.
cut and fill v: to cut down high ground or fill in low ground to achieve a uniform grade for a pipeline.
cut-and-fill boundary n: the limits to which a crew may cut and fill when laying a pipeline.
cut drilling fluid n: a drilling mud whose density has been decreased by the entrainment of formation fluids or air.
cut fluorescence test n: a test involving the observation of a formation sample immersed in solvent and under ultraviolet light. If any hydrocarbons, which fluoresce under ultraviolet light, are in the sample, they will dissolve and appear as streamers or streaks of colour different from the solvent.
cutoff valve n: a special valve on an engine that, when activated, blocks the flow of fuel to the engine to make it stop running.
cut oil n: an oil that contains water, usually in the form of an emulsion. Also called wet oil.
cutterhead n: in pipeline construction, the lead component in a directional drilling assembly. A circular steel band ringed with conical cutting teeth, the cutterhead does the actual boring of the hole for the pipeline under the waterway being crossed. Also called fly cutter.
cutters n pI: 1. on a bit used on a rotary rig, the elements on the end (and sometimes the
sides) of the bit that scrapes, gouges, or otherwise removes the formation to make hole. 2. the parts of a reamer that actually contact the wall of the hole and open it to full gauge. A three-point reamer has three cutters; a six-point reamer has six cutters.
Cutters are available for different formations.
cutting in n: an action of wire rope during loose drum spooling in which a layer of rope spreads apart so that the next layer travels in the groove produced. Crushing, flattening, or distorting of the rope results.
cuttings n pI: the fragments of rock dislodged by the bit and brought to the sulphur in the drilling mud. Washed and dried cuttings samples are analysed by geologists to obtain information about the formations drilled.
cuttings-sample log n: a record of hydro- carbon content in cuttings gathered at the shale shaker; usually recorded on the mud log.
CWA abbr: Oean Water Act.
cycle n: the number of strokes a piston makes from one intake stroke to another intake stroke. Diesel engines may have either two strokes or four strokes per cycle.
cycle condense n: condense produced from cycle gas.
cycle gas n: gas that is compressed and returned to the gas reservoir to minimise the decline of reservoir pressure.
cyclic compound n: a compound that contains a ring of atoms.
cyclic steam injection n: the injection of steam into the rock surrounding a production well to lower the viscosity of heavy oil and increase its flow into the wellbore. Steam injection may be followed by immediate production or by closing the well (called the soak phase) to allow even heat distribution before production is begun. The cycle of injection, soak, and production is repeated as long as the oil yield is profitable. Also called steam soak and huff 'n' puff.
cyclic stressing n: stress that occurs on a pipe. vessel. or machine in cycles. such as the sucker rod string.
cycling n: the process by which effluent gas from a gas reservoir is passed through a gas- processing plant or separation system and the remaining residue gas returned to the reservoir. The word recycling is sometimes used for this function, but it is not the preferred term.
cycling plant n: a plant that cycles residue gas back into the reservoir.
cyclogenesis n: the development of a low- pressure system, or cyclone.
cyclone n: 1. a low-pressure area, around which wind flow is counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The term is sometimes used to describe storms occurring in the atmosphere; in the Indian Ocean it is used to designate a tropical cyclone. 2. a device for the separation of various particles from a drilling fluid, most commonly used as a desander. The fluid is pumped tangentially into a cone, and the fluid rotation provides enough centrifugal force to separate particles by mass weight.
cyclonic wind n: the wind associated with a low-pressure area.
cyclonite n: a powerful, highly explosive material (cyclo-trimethylene-trinitramine) used as the main charge in jet perforating guns. Also called RDX. See jet-perforate.
cycloparaffin n: a saturated nonaromatic hydrocarbon compound with ring-shaped molecules. of the general chemical formula CnH2n' Also called naphthene.
cylinder n: 1. the unit of an internal- combustion engine in which combustion and compression take place. 2. a chamber in a pump from which the piston expels fluid.
cylinder n: 1. the unit of an internal- combustion engine in which combustion and compression take place. 2. a chamber in a pump from which the piston expels fluid.