Discover the IHRDC Energy Glossary_beta

R chart

A control chart used to plot the range of measurements in a sample group.

R h

Horizontal resistivity — resistivity measured with current flowing parallel to the bedding.

R signal

The part of an induction tool's received signal that is in phase with the transmitter current, carrying the formation conductivity.

R v

Vertical resistivity — resistivity measured with current flowing across the bedding.

R wa

Apparent water resistivity, computed from the resistivity and porosity logs as if the zone were fully water-bearing.

R-factor

The ratio of cumulative revenue to cumulative cost, used to slide the profit split as a project pays out.

rabbit

A drift gauge dropped or pushed through a tubular to confirm nothing smaller than the specified bore will obstruct it.

raceway

Any designed structure that cables and conductors follow.

raceway diagram

A drawing that shows the raceway layout in a specific plant or building.

RACI chart

rack room

The room housing control and protection equipment racks.

racking back pipe

Setting stands of pipe upright in the derrick's fingerboard as the string is pulled.

racking out

The act of physically disconnecting and removing a circuit breaker from a switchgear assembly to eliminate an electrical energy source.

radial

Relating to a line or direction, perpendicular to the shaft or axis of rotation.

radial array

A source or receiver array whose elements radiate outward from a common center.

radial bearing

A bearing that prevents shaft movement in any direction outward from the centerline of the shaft.

radial blade fan

A type of centrifugal fan in which the blades are flat and mounted radially to a hub so that air is pushed straight out from the hub.

radial differential temperature log

A record of the temperature difference between opposite sides of the casing wall at the same depth.

radial faulting

A set of faults whose planes strike outward from a common center, typically above a salt dome.

radial flow

Radial flow is the flow into the wellbore during a well test from a reservoir having no apparent outer boundary limit affecting the fluid flow during the test period, the direction of flow being perpendicular to the axis of the well.

radial impeller

An impeller that produces flow that is basically perpendicular to the shaft of a mixer.

radial load

Load acting perpendicular to the shaft axis.

radial movement

Movement perpendicular to the shaft axis.

radial processing

The joint inversion of resistivity curves of different depth of investigation into a radial model of invasion.

radial refraction

Refraction surveying with receivers on an arc around the source, to detect a buried high-velocity body from early arrivals.

radial resolution

How finely a logging measurement can distinguish changes with distance out from the borehole.

radial response

How a logging measurement responds as a function of distance out from the tool, perpendicular to the borehole.

radial thrust

A force exerted perpendicular to the centerline, or axis, of a shaft.

radially split pump

A pump with a casino that is split perpendicular to, or around, the axis of the pump's shaft. Sometimes caused a "barrel' pump or a -cartridge' pump.

radiant energy

Energy transferred as electromagnetic radiation, the dominant mode in a furnace.

radiant section

The tubes in a furnace that are in direct line of sight with the burner flame.

radiation

A mode of heat transfer in which heat is transferred through electromagnetic waves (infrared rays).

radiator

On a power transformer, typically an arrangement of tubes mounted externally on the transformer enclosure through which oil flows and through which heat is dissipated.

radii

The distances from the wellbore at which properties or pressures are evaluated.

radio repeater

A radio repeater is a combination of a radio receiver and a radio transmitter that receives a signal and retransmits it, so that two-way radio signals can cover longer distances.

radio silence

The shutdown of radio transmitters near the wellsite so stray energy cannot detonate perforating guns.

radio-safe detonator

An electric detonator designed not to fire from stray radio-frequency or static energy.

radioactive density analyzer

An analyzer that measures density without making direct contact with a process liquid.

radioactive tracer

A short half-life radioactive material released downhole and then logged to show where the fluid carrying it went.

radioactive, radioactivity, radioactive decay

The process by which a nucleus of an unstable atom loses energy by emitting ionizing radiation, including alpha particles, beta particles, gamma rays, and conversion electrons. A material that spontaneously emits such radiation is considered radioactive.

radioactive-tracer log

A log following radioactive material injected into the stream, to show where injected fluid is going.

radiographic inspection

Non-destructive testing in which X-rays or gamma rays passed through a weld or casting are recorded on film or a detector.

radioisotope

A radioactive material that will produce a constant amount of nuclear radiation.

radius

The distance from the center point of a circle to any point on its circumference; half the diameter.

radius investigation

How far from the borehole a measurement actually senses.

radius of curvature

A survey calculation method that joins successive stations with a smooth circular arc rather than a straight line.

radius of investigation

How far out from the wellbore a measurement actually senses the formation.

rag

The sludge-like, oily water mixture that collects at the water/oil interface in a desalter.

rail

The vertical lines on the left and right sides of a ladder diagram that connect the rungs.

raised face flanges

A flange designed so that the mating surface of the flanges extend out farther than the surface that contains the bolt holes.

raised-face flange

A flange with a raised area around the center upon which a gasket is usually compressed.

RAM

Random Access Memory, the storage area in a computer that contains active operating and program instructions.

ram blowout preventer

A preventer that seals by driving opposed rams together across the bore, around the pipe or on the open hole.

ram preventer

A blowout preventer that seals by driving opposed hydraulic rams together across the bore.

ramp

A controller enhancement that enables a process variable to be taken from a start point to a final set point in a series of controlled steps. The ramp function is typically used during startups to minimize thermal stress.

ramp rate

The change in temperature per unit of time during boiler warmup and shutdown.

ramp-and-soak control

A type of process control characterized by periods during which a process is stabilized before continuing to be ramped toward a setpoint.

ramping down

The process of gradually reducing temperature and pressure during boiler shutdown.

random decision forests (RDF)

Random Decision Forests are an ensemble learning method for classification, regression and other tasks that operates by constructing a multitude of decision trees at training time. For classification tasks, the output of the random forest is the class selected by most trees. For regression tasks, the mean or average prediction of the individual trees is returned. RDFs correct for decision trees' habit of overfitting to their training set.

random error

Scatter in repeated measurements that varies unpredictably in sign and size and tends to average out.

random noise

Seismic energy uncorrelated from trace to trace and unrelated to the source.

random packing

Loose shaped elements dumped into a column to provide contact surface, cheaper than structured packing and less predictable.

random variation

Variation with no assignable cause, which control charts distinguish from a real shift.

random-walk method

A stochastic technique that simulates a process as a sequence of random steps, and takes statistics over many realizations.

range

Range The low and high limits of a scale.

range control

A control on a test instrument that is used to determine the range of values that the instrument will measure.

range of load

The difference between peak and minimum polished rod load through a pumping cycle.

range uncertainty

The spread between low and high estimates, reported instead of a single figure.

ransomware

Malware that encrypts systems and demands payment, the Colonial Pipeline attack being the industry's case study.

rappers

Hammer-like devices that strike the plates of an electrostatic precipitator and dislodge particulates.

rarefaction

Rarefaction is the reduction of an item's density, the opposite of compression.

ratchet stop micrometer

An outside micrometer equipped with a ratchet stop to stop adjustment of the tool when the right amount of pressure is exerted.

ratchet wheel

A toothed wheel allowing motion in one direction only.

rate

In process control, the tuning parameter that applies derivative (PID) control, modifying the controller output according to the rate of change of the error or process variable. In mathematics, a comparison of two quantities through division.

rate of penetration (ROP)

How fast the bit deepens the hole, in feet or meters per hour.

rate of return

The gain or loss on an investment over a period, as a proportion of what was invested.

rate of shear

The velocity gradient across a flowing fluid — how fast adjacent layers move relative to each other.

rate of solution

The speed with which a solute dissolves in a solvent.

rate-dependent skin effect

The part of skin that grows with flow rate, caused by inertial non-Darcy pressure loss near the wellbore.

rated capacity (lifting capacity)

The amount of weight for a specific load center and maximum lift height that a forklift can safely lift and carry.

rated voltage

The voltage equipment is designed to operate at continuously.

rathole

A lined hole in the rig floor in which the kelly is stored when it is not in use.

ratio control

A control system designed to keep one or more dependent variables at a percentage of an independent variable.

ratio curve on pulsed neutron log

The ratio curve shown on pulsed neutron log displays is the ratio of the count rates of the near to the far detector.

rattail joint

A type of splice that is sometimes used in a junction box and for connecting branch circuits. Also called a rattail splice.

ravinement

An erosional surface cut by waves as the shoreline moves landward.

raw crude oil

Crude as it arrives from the well, before separation and treating.

raw natural gas

Natural gas as it is produced from the reservoir.

rawls' theory of justice

The argument that just arrangements are those chosen without knowing one's own position in them.

ray

A line drawn perpendicular to the wavefront, showing the direction seismic energy travels.

ray tracing

Computing traveltimes and paths by following rays through a velocity model.

Rayleigh wave

Rayleigh waves are a type of surface acoustic wave that travel on solids. They can be produced in materials in many ways, such as by a localized impact or by piezo-electric transduction, and are frequently used in non-destructive testing for detecting defects. They are part of the seismic waves that are produced on the Earth by earthquakes.

raymer-hunt equation

An empirical relation converting sonic transit time to porosity, improving on the time-average.

Raynaud's phenomenon

An MSD characterized by numbness and whitening of the fingers due to lack of blood supply, and with pain when subjected to cold temperatures. It is caused by significant exposure to vibration, such as when using heavy power tools.

raypath

The route seismic energy follows from source to receiver through the subsurface.

RC circuit

A circuit incorporating both resistance and capacitance.

RC oscillator

An oscillator that uses resistors and capacitors (connected in series) in its tuned circuit.

RCD

Rotating control device: a pressure-containing head that seals around the drillstring while it turns, closing the annulus so returns can be diverted.

RCRA

The Resource Conservation and Recovery Act: the 1976 US statute governing hazardous waste from generation through treatment, storage and disposal.

re-range

To reset the lower range value and the upper range value of a smart field device, either because of a process alteration or to use the device on another process.

reaching closure

Moving deliberately from open discussion to a committed agreement.

reactance

The vector sum of the inductive reactance and the capacitive reactance in a circuit. In electrical formulas, reactance is typically represented by a capital X.

reactant

A product of one reaction that is suitable and appropriate for use as a feed or charge material for another reaction.

reaction

In turbines, a type of blade that causes the wheel to rotate when high-speed steam forces the blades opposite the flow direction. In process engineering, an operation used to change the form of materials under carefully controlled conditions.

reaction rate

A measure of the amounts of reactants that are converted into products in a given period of time.

reaction section

The section of an alkylation unit in which the process reactions occur and in which the catalyst is separated from the reacted and unreacted hydrocarbons.

reactivation

Renewed movement on an existing fault, which can breach a seal that held for millions of years.

reactive power

Power that goes back and forth between a power source and an inductive or capacitive device.

reactivity

The tendency of a substance to undergo a chemical change or reaction, describing how a chemical interacts with other substances or how its characteristics might change under some conditions, potentially involving a release of energy such as an explosion.

reactivity hazard

A material that poses a risk of a violent chemical reaction.

reactor

A vessel or tank used to combine or convert raw materials into products by chemical reactions. In a cat cracker, it is where cracked gas is disengaged from spent catalyst. In protective relaying, a component of a filter circuit that functions like an induction coil, working with capacitors to produce voltage across a voltage coil.

reactor effluent

The stream leaving the reactor.

reactor process system

A process system that contains a reactor.

reactor system

The reactor with its feed, heat and effluent equipment.

reactor temperature

The temperature inside a reactor, which sets conversion and selectivity.

readout

The displayed value of an instrument.

reagent

A substance added to produce a chemical reaction in an analysis.

reagents

Chemicals added to produce a specific reaction in a test or process.

real property

Land and what is permanently attached to it.

real time

Real time is used to distinguish reporting, depicting, or reacting to events at the same rate and sometimes at the same time as they unfold, rather than compressing a depiction or delaying a report or action.

real time, real-time

Real-time or real time is used to distinguish reporting, depicting, or reacting to events at the same rate and sometimes at the same time as they unfold, rather than compressing a depiction or delaying a report or action.

real-time data

Information concerning the current status of some variable. For example, present temperature, pressure, or speed.

real-time sampling

A sampling mode in which an oscilloscope collects as many samples as it can as a signal occurs.

ream

To enlarge or clean up a hole already drilled, by running the bit or a reamer back through it.

reaming

Reaming is an additional operation when drilling a borehole that may be done to part or all of the borehole. Reaming is conducted to enlarge the hole to its planned diameter. Several possible reasons account for the diameter of the borehole being smaller than planned, for example, the drill bit could be worn and thus smaller diameter, which results in an under-gauge hole.

reasonable accommodation

An adjustment enabling a disabled employee to perform the job.

reasonable certainty

A high degree of certainty. Much more likely to be achieved than not.

reasonableness test

Checking a figure against independent expectation rather than only against its supporting record.

reasoning fallacy

A flaw in argument structure that makes a conclusion unsupported even when it sounds persuasive.

reboiler

A type of shell and tube heat exchanger used to heat and vaporize the bottoms product and lighter products in a distillation column. Also, the vessel that generates steam at the bottom of a stripper to strip acid gases from rich amine solution.

reboiler (reconcentrator)

The vessel where water is boiled out of the glycol.

reboiler fire tube

The tube carrying combustion gas through the reboiler liquid, and where glycol degrades if the wall gets too hot.

reboiler heat

The heat input regenerating the solvent, and the largest energy demand in a dehydration unit.

reboiler overload

Heat input beyond what the reboiler can pass without overheating the liquid film and degrading it.

reboiler still column

A vertically mounted vessel on top of the reboiler where glycol vapors condense and water vapors are released.

reboiler temperature

The reboiler's temperature, which sets how dry the regenerated solvent gets and how fast it degrades.

receivables

Amounts owed by customers, and a working capital item that ties up cash.

receiver

A component in a refrigeration system that stores liquid refrigerant under pressure. In sonic level measurement, the part that receives sound waves after they bounce off the liquid surface and converts sound energy to electrical energy.

receiver array

A receiver array is a group of receivers that are connected together, traditionally by wires, although cableless receivers are now available.

receiver group

Several receivers combined into one recording channel.

receiver line

The line along which receivers are laid out in a survey.

receiver location

Where a receiver actually sat, which positioning error turns into imaging error.

receiver static

The timing correction belonging to a receiver position.

receiver stations

A receiver station is generally considered a shotpoint location to which specific receivers are located.

receiving

The first step of a production process, in which incoming feedstocks and materials are checked and regulated.

receptacle

A profile in the completion designed to receive and hold a tool.

recertification

Periodic reassessment or continuing study required to keep a credential valid.

reciprocate

To move a string up and down in the hole without rotating it.

reciprocating

A back and forth, straight-line motion; a device that has forward and backward motion.

reciprocating compressor

A device for raising gas pressure using reciprocating motion.

reciprocating motion

Back-and-forth linear motion, the working stroke of both rod pumps and piston compressors.

reciprocating pump

A type of positive displacement pump that uses a piston, diaphragm, or other device moving in a back-and-forth motion to move fluid.

reciprocating rod pump

A downhole pump worked up and down by a rod string.

reciprocating saw

A relatively heavy-duty, portable power saw that has a blade mounted at the end of the using. The blade cuts with a back-and-forth, horizontal motion.

reciprocation

Moving pipe up and down, used during cementing to improve mud displacement.

recirculate

Return part of a flow to its source.

recirculated

Returned and passed through the system again.

recirculating mixer

A mixer that recycles slurry through the mixing tub, giving more consistent density than a single-pass jet mixer.

recirculation

Returning part of a flow to its source, to protect a machine or maintain velocity.

recirculation line

The line returning part of a flow to the machine's suction.

reclaimer

Unit boiling contaminants out of a circulating solvent so the inventory can stay in service.

reclose

Close again automatically after a protective trip, used on distribution circuits where faults are often transient.

reclosing relay

A relay designed to reclose a circuit breaker after it has been tripped.

recommendation system

An algorithm proposing the next action or item based on patterns in prior data.

recommissioning a tank

The process of putting an out-of-service storage tank back online.

recommissioning checklist

A checklist of inspections or other procedures that are performed during a recommissioning operation.

recompletion

The process of entering an existing wellbore and performing work designed to establish production from a new zone.

record

The set of traces from all channels for a single seismic shot.

recordable cases

As related to health, safety and environment (HSE), recordable cases include occupational death, nonfatal occupational illness and those nonfatal occupational injuries which involve one or more of the following: loss of consciousness, restriction of work or motion, transfer to another job or medical treatment (other than first aid).

recordable incident

An injury meeting the regulatory threshold for inclusion in reported statistics.

recorded data

Measurement-while-drilling data written to downhole memory and read out at surface, rather than pulsed up in real time.

recorder

A device or instrument that indicates the value of one or more process variables at the time of reading and provides a record of the values over a period of time.

recorder carrier

The downhole sub that houses and positions a pressure recorder in a test string.

recorder controller

A process control instrument that performs a recording function and a controlling function.

recording psychrometer

An analyzer that is used for continuous humidity measurements.

recoverable

Capable of being produced, as distinct from merely present in the rock.

recoverable gas lift gas

Lift gas that returns to surface and is taken into the sales or fuel stream rather than recompressed and reinjected.

recoverable reserves

The portion of hydrocarbons in place that can actually be brought to surface.

recovery

The fraction of the hydrocarbon in place that has been or can be produced.

recovery efficiency

Recovery efficiency is a numeric expression, expressed as a percentage, of that portion of the in place hydrocarbon quantities of petroleum estimated to be recoverable.

recovery factor

The recovery factor is the hydrocarbon recovery per unit volume of an oil or gas field, usually expressed in barrels per acre-foot, or cubic feet per acre-foot.

recovery forecast

A prediction of how much a well, reservoir or field will ultimately produce, and on what schedule.

recovery tank

A tank used to store off-spec materials, by-products from processes, and wastes from which valuable products or components can be recovered; also called a slop tank.

recovery waterflooding

Producing additional oil by injecting water to maintain pressure and sweep.

recruitment analytics

Measuring the hiring process to find where candidates are lost and cost is incurred.

recruitment strategy

The deliberate plan for where and how to find the people needed.

rectangle

A four-sided shape with four 90 angles.

rectification

The process of changing AC voltage to pulsating DC voltage.

rectifier

An electronic device or circuit that allows alternating current to flow in only one direction, thereby changing AC to pulsating DC voltage.

rectifier bridge

The part of a variable speed drive (typically a DC drive) that changes applied AC into DC.

rectifier circuit

A circuit converting alternating to direct current.

recurved spit

A recurved spit is a spit whose outer end is turned landward by current deflection, by the opposing action of two or more currents, or by wave refraction.

recycle compressor

The compressor returning unreacted gas to the reactor inlet.

recycle line

The route returning flow to an earlier point, used for control rather than for processing.

recycle valve

A valve which allows compressed gas to recycle from the discharge line back into the suction line of the cylinder.

recycled gas

Gas that stays in the mud after it reaches surface and is pumped back down the hole with it.

red beds

Sedimentary rocks (typically sandstone, siltstone, and shale) that are predominantly red in color due to the presence of ferric oxides, which typically occur as a coating on the grains of sediments.

red mud

A lime-treated water mud deflocculated with tannates, which gave it a characteristic reddish color.

redox

A paired reaction in which one substance loses electrons and another gains them.

redox reaction

A reaction that involves a transfer of electrons from one atom, molecule, or ion to another.

reduced voltage start motor controller

A motor controller that reduces the amount of power supplied to a motor during start up to limit high inrush current and reduce start up torque.

reduced-water slurry

A cement slurry mixed with less than the normal water, giving higher density and strength without additives.

reducer

A fitting joining pipe of two diameters.

reducing agent

A chemical added to an acid treatment to hold dissolved iron in its ferrous state so it cannot precipitate.

reducing connector

A crimp-on connector that is used to splice together two wires of different sizes.

reduction

In chemistry, a reaction in which a substance gains electrons. In catalysis, a stage of catalyst regeneration in which oxygen is removed from the catalyst surface.

reed switch

A device used to close and open an electrical circuit; consists of a pair of contacts, each mounted on a flexible metal strip, that are closed or opened by the introduction of a magnetic field around the switch.

reed valve

A suction or discharge valve that uses reeds (or strips) which lift and seat by differential pressure to control gas flow. This valve is used for low pressure compression requirements.

reef

A wave-resistant carbonate buildup constructed by organisms, standing above the surrounding sea floor.

reef talus

Reef talus is massive, inclined strata composed of reef detritus deposited along the seaward margin of an organic reef.

reefal

Pertaining to or made up of reef material.

reefs

A reef is a rock, sandbar, or other feature lying beneath the surface of the water, often 80 meters or less beneath low water.

reel

The powered drum that stores the coiled tubing string and spools it in and out of the well.

reel back tension

The pull maintained between the reel and the injector so the coiled tubing stays under control and spools evenly.

reeled tubing

Another name for coiled tubing — continuous pipe carried on a spool and run into the well without connections.

reeve

To pass, or thread, rope around the sheaves in a block.

reference check

Verifying a candidate's account of their history and conduct with previous employers.

reference fuels

Fuels that have undergone multiple lab tests and have a guaranteed octane number.

reference junction

A point on the non-inverting input terminal of an op amp circuit at which the voltage is said to be the reference voltage for the op amp's summing junction.

reference point

The fixed point on a tool string or vessel from which all other positions and depths are measured.

reference voltage

The voltage in a comparator that the input signal is compared to; often zero volts.

refined petroleum product

Any saleable output of a refinery.

refined product

Any saleable output of a refinery, from gasoline to bitumen.

refiner

A company that runs refineries, buying crude and selling products.

refinery

A group of plants or units that work together to produce a variety of products.

refinery addition

New refining capacity brought into service.

refinery complexity

The measure of conversion capacity relative to distillation, which predicts margin capability.

refinery configuration

The particular set of process units a refinery has, which fixes what crudes it can run.

refinery fuel

The portion of throughput a refinery burns to run itself.

refinery margin

The difference between what a refinery's products fetch and what its crude and operating costs are.

refinery market

The market a refinery supplies, which shapes its product slate.

refinery output

The volume and mix of products a refinery produces.

refinery petrochemical plant

An integrated site combining refining with chemical production.

refinery run

The volume of crude a refinery processes over a period.

refinery scheduling

Sequencing crude runs and unit rates day by day to hit the planned product slate.

refining capacity

The volume a refinery or region can process, usually quoted per day.

refining center

A region with concentrated refining capacity serving a wide market.

refining complexity

The extent of a refinery's conversion capability.

refining crude oil

Converting crude into saleable products.

refining industry

The sector converting crude oil into saleable products.

refining margin

The difference between the value of a refinery's products and the cost of its crude.

reflectance

The proportion of light a surface reflects, measured on vitrinite to establish thermal maturity.

reflection

The return of wave energy from an interface between materials of differing properties.

reflection amplitude

The strength of a reflected arrival.

reflection coefficient

The ratio of reflected to incident amplitude at an interface, set by the acoustic impedance contrast across it.

reflection pulse

The wavelet returned from an interface.

reflection seismic

Imaging the subsurface from waves reflected at interfaces.

reflection tomography

The inversion of many reflected traveltimes into a three-dimensional velocity model of the subsurface.

reflective listening

Restating what was said to confirm understanding before responding.

reflectivity

Another term for reflection coefficient — reflected amplitude divided by incident amplitude.

reflectivity series

The sequence of reflection coefficients with depth, what seismic is trying to recover.

reflector

An interface across which acoustic impedance changes enough to return seismic energy.

reflux

Condensed overhead product that is pumped back into the top of a distillation column to control temperatures. Also, the process of condensing vapor to liquid so it falls downward in a still column while allowing lighter vapor to continue rising. Generally, a process where a fluid is removed from a vessel, condensed, and returned to enhance the process.

reflux accumulator

Vessel collecting condensed overhead before it is returned as reflux or drawn as product.

reflux coil

Coil located in the top of still column to aid in condensation of glycol vapor.

reflux condenser

Condenser returning part of the overhead as liquid, improving separation in the column below.

reflux flow

The rate of condensed overhead returned to a column, the main handle on separation.

reflux liquid

A cooler liquid that is circulated through coils in the reboiler still column to condense glycol vapors.

reflux pump

Pump returning condensed overhead to the top of a column.

reflux rate

The rate at which reflux is pumped back into a distillation column.

reflux ratio

The ratio between the amount of overhead product returned to a distillation column as reflux and the amount sent to storage.

reformate

A high-octane, high-quality gasoline feed produced from a charge material by a catalytic reforming process, sent to the gasoline blending area.

reforming

A chemical modification that converts a charge material into a higher-octane product called reformate.

reforming catalyst

The platinum-bearing catalyst rearranging naphtha molecules to raise octane.

reforming reaction

The catalytic rearrangement of naphtha molecules to raise octane, releasing hydrogen.

reforming unit

The refinery unit converting naphtha to high-octane reformate and hydrogen.

reformulated gasoline

Gasoline blended to reduce emissions, mandated in areas with poor air quality.

refracted

Bent on crossing a velocity boundary, the basis of refraction surveying.

refraction

The bending of a ray as it crosses into a medium of different velocity, governed by Snell's law.

refractive index

The speed of light in vacuum divided by its speed in the material, symbol n.

refractor

A layer fast enough and thick enough to carry a head wave along its top, and so to be mapped by refraction.

refractory

Heat-resistant material used to line a furnace shell.

refracturing

A second fracture treatment on a well that has already produced, to restore or improve its rate.

refrigerant

A fluid used in a refrigeration system to transport heat, which boils at relatively low temperatures and liquefies under pressure higher than atmospheric.

refrigerant compressor

The compressor driving a refrigeration loop, raising refrigerant pressure so it can reject heat.

refrigerant compressor oil

Lubricant in the refrigeration compressor, whose carryover fouls the chiller it reaches.

refrigerant flow

The refrigerant circulation through a refrigeration loop.

refrigerant vapor

Refrigerant in gas phase, on its way from evaporator to compressor.

refrigerated ship

A vessel carrying LPG or chemicals at low temperature rather than under pressure.

refrigerated tank

A tank that has been modified to contain materials at low temperatures.

refrigeration

A process of cooling by transferring heat out of a substance or area. In gas processing, a method for chilling a natural gas stream to remove NGLs.

refrigeration cycle

The compress, condense, expand and evaporate sequence that moves heat against its gradient.

refrigeration system

A system that controls air temperature in a conditioned area.

refueling

Replenishing a vehicle's stored fuel, and for hydrogen the operation that competes with battery charging on time.

regasification

Warming LNG back to gas at the importing terminal for delivery into the pipeline network.

regenerable fixed-bed system

A carbon adsorption system that allows one carbon bed to be desorbed while a second carbon bed removes contaminants from a gas stream.

regenerate

To separate the acid gases from the amine solution.

regenerated catalyst

Catalyst restored to activity by burning off coke.

regenerating section

In an amine treatment unit, the section in which the H₂S is stripped from the amine so that the amine may be used again. In a mercaptan extraction system, the section in which mercaptans are converted to disulfides and then separated from the caustic so that the caustic may be used again.

regeneration

The process of purifying and reusing glycol (after it has absorbed water and hydrocarbons) or amine solution (after it has absorbed acid gases).

regenerative process

Process of purifying the glycol after it has absorbed water and hydrocarbons.

regenerator

The vessel in a cat cracking unit in which coke deposits are burned off of spent catalyst so that the catalyst can be reused.

regional dip

The prevailing tilt of beds across an area, on which local structure is superimposed.

regolith

Regolith is a blanket of unconsolidated, loose, heterogeneous superficial deposits that cover solid rock. It includes dust, broken rocks, and other related materials.

regressing

Regression occurs when the sea level drops and the shoreline moves away from land, exposing areas of the seafloor that were previously submerged.

regression

The seaward migration of the shoreline as sediment progrades into the basin or relative sea level falls.

regression coefficient

The slope term of a fitted regression line, giving the change in the response per unit change in the predictor.

regressive

Regression is a geological process where, due to a falling sea level, the shoreline moves seaward causing the water to move away from the land, exposing previously submerged areas to weathering. Transgression is the opposite process where, due to a rising sea level, the shoreline moves landward, often flooding low-lying areas.

regular gasoline

The lowest octane grade sold at retail.

regular lay

A form of wire rope construction in which the strands of the rope spiral in one direction while the wires that make up the strands are wound in the opposite direction.

regulated pipeline accounting

Accounting for a utility whose allowed return is set by a regulator rather than by the market.

regulation

In drives, how closely speed matches the set speed, a function of how well feedback modifies a command signal. In power supplies, how well a constant voltage is maintained to a load regardless of changes in source voltage or load resistance.

regulator

In oxy-fuel welding, the component attached to a cylinder valve that reduces high cylinder pressures to working pressures and maintains steady gas flow. In electronics, a circuit that maintains a constant voltage to a load regardless of changes in source voltage or load resistance.

regulators

On a gas-sealed power transformer, devices that control the flow of gas from a gas cylinder to the transformer enclosure. The regulators also reduce the high pressure in the cylinder to a safer, lower pressure in the transformer enclosure.

regulatory body

The government or industry authority that sets the rules an operation must meet and verifies compliance.

regulatory compliance

Meeting the legal and sector requirements applying to information handling.

regulatory law

The body of rules made by agencies rather than legislatures, and how they are challenged.

regulatory scrutiny

Heightened official attention, usually following an incident or political pressure.

rehearsal

Practicing aloud under conditions resembling the real thing.

reheat steam

Steam returned to the boiler for reheating between turbine stages, raising cycle efficiency.

reheat steam system

A system that increases the energy of steam exhausted from the HP section of the turbine before it enters the IP section.

reheat stop

The valve isolating reheat steam to the turbine.

reheat stop valve

A valve that stops the flow of steam to the IP section of the turbine in case of turbine overspeed. Controlled by the turbine control system.

reheater

A boiler component that adds heat to steam after it has moved through a portion of the turbine. The reheated steam then flows through the remainder of the turbine.

Reid vapor pressure (RVP) analyzer

An analyzer that may be used to measure vapor pressure during an inline blending process.

Reid vapour pressure (RVP)

A standard measure of how readily a fuel vaporizes, limiting summer gasoline volatility.

reinforcement and recognition

Responding to good performance so it is repeated, the cheapest management lever available.

reinforcement learning

Training in which a system learns by acting, receiving a reward or penalty, and adjusting toward higher reward.

relationship management

Building and maintaining the working relationships that get things done.

relative age

The age of a rock expressed as older or younger than another, without assigning it a number of years.

relative dielectric constant

A material's permittivity divided by that of free space — how much charge it can store relative to a vacuum.

relative dielectric permittivity

Relative dielectric permittivity is the degree to which a medium resists the flow of electric charge divided by the degree to which free space resists such charge. The degree, or dielectric permittivity, is defined as the ratio of the electric displacement to the electric field strength. The term is also known as the relative dielectric constant.

relative filtrate volume

Twice the filtrate collected between 7.5 and 30 minutes of a filtration test.

relative humidity

The amount of water vapor in air compared to the amount of water vapor that the air could hold at a given temperature and pressure.

relative permeability

A dimensionless measure of the effective permeability of a phase in multiphase flow through porous media. It is the ratio of the effective permeability of that phase at a particular saturation to the absolute permeability at total saturation.

relative permeability curve

The plot of each phase's permeability against saturation, which governs how a displacement actually proceeds.

relative volatility

The ratio of two components' tendencies to vaporize, which decides how easily distillation separates them.

relaxation time

The characteristic time over which excited protons return to equilibrium in a nuclear magnetic resonance measurement.

relaxation, nuclear magnetic relaxation

Relaxation is the processes by which an excited magnetic state returns to its equilibrium distribution. Nuclear magnetic resonance relaxation measurement can be used for spectral assignment and the study of quadrupolar and paramagnetic interactions, and exchange dynamics.

relaxed-filtrate oil mud

An oil mud deliberately built with few colloidal solids, so it gives up a controlled amount of oil filtrate instead of almost none.

relay

A device that responds to changes in current or voltage in a circuit to operate contacts in the same circuit or in a different circuit.

relay circuit

A circuit built from relays.

relay coil

The coil energizing a relay.

relay contact

The switching contact a relay opens or closes.

relay logic

Control logic implemented in relays rather than in software.

relaying

Protection by relays, and the discipline of setting them to coordinate.

release joint

A tool designed to part on command, separating the string above from the assembly below.

release lever

The lever freeing a latch or mechanism.

release plan

The schedule of what functionality is delivered in which release.

relief device

Any device that is used either to vent off vapors that cause excess pressure, or to admit air or a gas into an area to prevent pulling a vacuum.

relief valve

A valve that opens (slowly or proportionally) to relieve excess pressure in a system and then closes automatically. Used to protect equipment from overpressure and often installed near the discharge of positive displacement pumps. Also known as pressure-relief valve, safety valve, or pop valve.

relieve pressure

Release pressure to prevent equipment being overpressured.

relinquishment

At the beginning of the Exploration Period, a Contractor usually has a large “block” or area to explore; however, as each exploration phase concludes, a portion—often around 20% of the area—must be relinquished or returned to the government for potential issuance to another company.

remaining oil saturation

The oil still present in the pore space at a given place and time, whether it is movable or not.

remanent

Retained magnetization recording the field direction when the rock formed.

remedial cementing

Any cementing done to repair a well problem rather than to place the original sheath.

remittance

The payment sent to settle an invoice, and the advice identifying what it covers.

remote control

A type of device that allows a welder to control the operation of a welding machine while welding.

remote I/O

An Allen-Bradley network for connecting PLC-5 processors, remote I/0 chassis, PCs, and HMIS together.

remote I/O network

Allen-Bradley's proprietary network for connecting I/O racks and high-end HMIs together.

remote rack or chassis

A rack of I/O modules in a PLC system that is connected to the local rack containing the processor module. There may be several such racks in a system.

remote racks

The logical racks in a PLC system chassis that do not have the PLC processor in them.

remote sensing

The acquisition, processing and interpretation of images of the Earth taken from aircraft or satellites.

remote set point (RSP)

The set point provided to a controller from another part of a loop; often the set point provided by the primary loop in a cascade system.

remote work

Working away from the employer's premises, usually from home.

remotely operated vehicle

An unmanned submersible flown from surface on an umbilical, used for subsea inspection and intervention, abbreviated ROV.

renegotiation

Reopening agreed terms, usually because circumstances or the balance of power has changed.

renewable electricity

Power generated from renewable sources, the input that determines whether electrolytic hydrogen is clean.

renewable energy

Energy from sources that replenish on a human timescale, so the fuel cost is nil and the capital cost is everything.

renewable energy source

A specific origin of renewable supply, such as solar, wind, hydro or biomass.

renewable hydrogen

Hydrogen made with renewable electricity or biomass, distinguished by input rather than by process.

renewable resource assessment

Measuring the wind, solar or biomass resource at a site to size and value a project.

renewable-link fuse

A fuse that can be used again after its blown fuse link is replaced with a new one.

repeat section

A short interval logged a second time to demonstrate that the measurements are reproducible, usually about 200 ft.

repeatability

A characteristic required of a flow meter in which volume measured must be within 0.05% for five of six consecutive trips.

repeatable

Giving the same result on remeasurement, the basic test of a log or an experiment.

repetition

An ergonomic risk factor that involves performing the same motions over and over again with little variation. Repetition can gradually wear on muscles and tendons, even if the force required is low, because of inadequate time for them to recover.

replaceable

Designed to be changed out rather than repaired in place.

replacement velocity

The velocity assigned to the material between the datum and the base of the weathered layer when static corrections are computed.

reproducibility

The agreement between results for the same material obtained under different conditions — different operator, apparatus or laboratory.

reproductive toxins

Chemicals that affect the reproductive capabilities, including chromosomal damage (mutations) and effects on fetuses (teratogenesis).

reputational risk

Exposure to loss of standing, which can cost more and last longer than the triggering event.

requirements

The stated conditions a solution must satisfy.

requirements analysis

Examining stated requirements for conflict, gaps and feasibility.

requirements elicitation

Drawing out requirements from stakeholders, who rarely state them completely unprompted.

requirements prioritization

Ranking requirements so the most valuable are delivered first.

requirements tracing and monitoring

Tracking each requirement through to the delivered feature that satisfies it.

Requisition to Pay (RtP)

The controlled sequence from raising a requirement to paying the supplier's invoice.

rerun column

A type of acid regenerator that uses a stream of hot isobutane to strip out HF acid from contaminants.

rescue service

The personnel designated to rescue employees from permit spaces.

reservation price

The least favorable price a party would still accept rather than walk away.

reservation value

The least favorable terms a party would still rationally accept.

reserve estimation

Quantifying recoverable volumes to an agreed standard of certainty.

reserve pit

An earthen pit at an onshore location holding waste mud and cuttings until they are disposed of.

reserve quantities

The volumes disclosed in a company's reserves statement, audited and reported annually.

reserve quantities disclosure

The supplementary statement of reserves volumes and value that oil and gas companies must publish.

reserve-mud pit

A pit holding mud that is not part of the active circulating system.

reserves

Estimated remaining quantities of oil, gas, and related substances anticipated to be commercially and economically producible by application of development projects to known accumulations from a given point forward, justified for development. There must exist, or be reasonable expectation of, the legal right to produce, installed means of delivery, and all required permits and financing.

reserves estimation

Quantifying how much of the hydrocarbon in place can be recovered commercially.

reserves replacement

The ratio of new reserves booked to volumes produced in the same year.

reservoir

A subsurface body of porous and permeable rock containing an individual and separate natural accumulation of moveable petroleum, confined by impermeable rocks or water barriers and characterized by a single pressure system.

reservoir area

The plan-view extent of the accumulation.

reservoir characteristic

Any measured property describing the reservoir rock or its fluids.

reservoir characterization

The process of building a model of a reservoir that incorporates all characteristics pertinent to its ability to store and produce hydrocarbons. These models are used to simulate fluid behavior under different conditions and find optimal production techniques to maximize recovery. Some data is derived from cuttings, core analyses, and other geologic studies.

reservoir characterization model

A three-dimensional model of the reservoir carrying its geological properties cell by cell.

reservoir communication

Fluid movement between parts of a reservoir, or between reservoirs, showing they are hydraulically connected.

reservoir compaction

Compaction that occurs as hydrocarbons are produced from a reservoir and pore pressures decline, causing effective stresses to increase.

reservoir condition

The in-situ pressure and temperature, at which fluid volumes and properties differ sharply from surface.

reservoir data

The logs, cores, tests and production history describing a reservoir.

reservoir depletion

Reservoir depletion is the decline in the hydrocarbons within a reservoir. Oil depletion is the decline in oil production of a well, or oil field.

reservoir depletion, depleted reservoir

A depleted reservoir can be defined as a reservoir that has produced oil or gas.

reservoir description

The geological model of how rock and fluid properties are distributed through a reservoir.

reservoir development

Putting in the wells and facilities to produce a discovered accumulation.

reservoir drive mechanism

The natural energy producing the reservoir, such as water drive or solution gas.

reservoir drive mechanisms

The natural energy sources that move hydrocarbons to the wellbore — solution gas, gas cap, water drive, compaction and gravity drainage.

reservoir engineer

The engineer responsible for forecasting and optimizing recovery from a field.

reservoir engineering

The discipline of predicting and managing how much hydrocarbon a reservoir will give up and how fast.

reservoir evaluation

Establishing what a reservoir holds and what it will produce.

reservoir facies

The rock types within the reservoir and their spatial arrangement.

reservoir fluid

The oil, gas and water occupying the pore space, whose behavior governs recovery.

reservoir fluid property

The composition, viscosity and phase behavior governing how the fluid flows.

reservoir geological model

The rock framework model the flow simulation is built on.

reservoir height

The vertical thickness of reservoir open to flow at the well.

reservoir heterogeneities

The variations in rock properties from place to place within a reservoir.

reservoir heterogeneity

Variation of rock properties within the reservoir, which decides sweep more than average properties do.

reservoir interval

The depth range holding the reservoir.

reservoir lithology

The rock type of the reservoir, which governs porosity and how it is stimulated.

reservoir management

Operating a field over its life to maximize recovery and value rather than short-term rate.

reservoir model

The numerical description of the reservoir used to forecast production.

reservoir modeling

The construction of a computer model of a petroleum reservoir for the purposes of improving the estimation of reserves and making decisions regarding the development of the field. Reservoir models typically fall into two categories: a) geological models are created by geoscientists and aim to provide a static description of the reservoir, prior to production. b) reservoir simulation models are created by reservoir engineers and use finite difference or streamline methods to simulate the flow of fluids within the reservoir over its production lifetime.

reservoir monitoring

Watching pressure, rates and fluid movement through field life to steer development.

reservoir oil

The oil as it exists at reservoir conditions, before shrinkage at surface.

reservoir parameter

A property the reservoir's behavior depends on, such as porosity, permeability or saturation.

reservoir performance

How a reservoir actually produces against what was forecast.

reservoir permeability

The reservoir's ability to transmit fluid.

reservoir porosity

The pore fraction of the reservoir rock.

reservoir pressure

The pressure of the fluid in the pore space of a reservoir.

reservoir property

A measured attribute such as porosity, permeability or saturation.

reservoir quality (RQ)

A composite measure of how well a rock can store and deliver hydrocarbons — porosity, permeability and saturation together.

reservoir rock

Porous, permeable rock capable of holding and yielding hydrocarbons.

reservoir sand

A sand body capable of holding and yielding hydrocarbons.

reservoir simulation

The numerical solution of fluid flow through a gridded reservoir model, run forward in time.

reservoir simulator

The numerical program solving flow equations over a gridded reservoir model.

reservoir study

An integrated review of a reservoir made to decide how to develop or manage it.

reservoir surveillance

Reservoir surveillance, starting with the data acquisition from the wells and the production network, is to obtain data for evaluating well and reservoir performance, reserves evaluation and finally, the foundation development, on which development options are optimally selected and decisions are made.

reservoir temperature

The in-situ temperature, which fixes fluid viscosity and phase behavior.

reservoir trap

A reservoir trap consists of an impervious stratum that overlies the top and side of the reservoir rock, thereby prohibiting hydrocarbons from escaping upward and laterally.

reservoir unit

A distinct flow layer within the reservoir.

reservoir volume

The bulk volume of rock holding the accumulation.

reset

The tuning parameter that applies integral (PID) control, modifying the controller output according to the time integral of the error.

reset contacts

Contacts in a reclosing relay that turn the motor off with the relay in the "start" position.

reset windup

The increasing reset correction that builds up before a process variable responds.

residence time

How long fluid stays in a vessel, set by the vessel's liquid volume divided by the throughput.

residual

In statistics, the difference between the observed value and the mean value that a model predicts. In refining, leftover material that collects in the bottom of an atmospheric distillation tower.

residual bend

The permanent curvature a length of coiled tubing keeps after being unspooled and left unstressed.

residual chlorine

The amount of chlorine left over in water after micro-organisms have been killed.

residual energy

Hazardous energy that is present in equipment even when no source of power is connected.

residual fuel

A heavy fuel made of residuals, or tower bottoms; used for firing boilers or furnaces. Also called bunker oil or #6 fuel oil.

residual fuel oil

The heavy bottoms remaining after distillation, burned in ships and power plants.

residual gravity

The gravity field left after removing the regional trend, which shows local structure.

residual oil

The oil left in the pore space that cannot be moved by continued flooding, held by capillary forces.

residual oil saturation

The fraction of pore volume occupied by oil at the end of oil displacement using a specific fluid (ROS). It signifies the ultimate recovery under a given displacement process and represents the end point of relative permeability curves. It is the saturation achieved after an infinite number of pore volumes of displacing fluid have flowed through the rock. Depends on flow rate, permeability, capillary end effects, test methodology, and the test laboratory.

residual oil/gas saturation

Residual oil/gas saturation is the oil/gas that cannot be mobilized and recovered from a rock.

residual static

The small timing error left after the main static correction, removed by cross-correlation.

residual statics

The small remaining time shifts corrected late in seismic processing to sharpen the stack.

residuals

In statistical models, a residual is the difference between the observed value and the mean value that the model predicts for that observation.

residue gas

Gas after being processed with the liquids removed.

residuum

The heavy material remaining after distillation.

residuum fraction (also known as residue, or residual)

The fraction containing the heaviest hydrocarbons (over C33) with the highest boiling points (over 800°F).

resilience

The capacity to recover function after setback or sustained pressure.

resin

A high molecular weight polar fraction of crude oil, intermediate between the oil and the asphaltenes it keeps in suspension.

resin bead

The small sphere of ion exchange resin that does the work in a demineralizer.

resin beads

Small, porous, plastic beads used in ion exchangers.

resistance

An electrical property that opposes or restricts the flow of current through a circuit, measured in ohms. In process control, any opposition to flow. In electrical formulas, resistance is typically represented by a capital R.

resistance temperature detector (RTD)

A type of temperature measurement device that measures temperature changes in terms of changes in electrical resistance.

resistance temperature device (RTD)

A variable resister which measures winding temperatures in an electrical motor.

resistance to change

Opposition to a change, usually rational from the resister's position and worth understanding.

resistive

Opposing the flow of electrical current, the log response that indicates hydrocarbons.

resistive circuit

A circuit whose impedance is resistance alone, with no reactance.

resistive invasion

Invasion in which the flushed zone is more resistive than the undisturbed formation.

resistivity

An intrinsic property that quantifies how strongly a material opposes the flow of electric current. The inverse of conductivity. Resistivity is a property of the material itself, while resistance also depends on the volume measured. The two are related by a system constant (length divided by area).

resistivity curve

The logged trace of formation resistivity against depth.

resistivity device

The tool measuring formation resistance to electrical current.

resistivity factor, formation resistivity ratio

The resistivity factor, or formation resistivity ratio, is the ratio of the resistivity of the rock saturated with brine (Ro) to the resistivity of the brine (Rw).

resistivity imaging

Producing a picture of the borehole wall from closely spaced resistivity measurements.

resistivity imaging tool

A tool making a picture of the borehole wall from many resistivity buttons.

resistivity index

The ratio of the true resistivity (Rt) to the resistivity of the same rock filled with water (Ro). It is related to water saturation by the saturation exponent n (I = Sw⁻ⁿ), and is a key component of the Archie equation.

resistivity log

A record of formation resistivity against depth, in ohm-m.

resistivity logging

Measuring formation resistance to current, the primary saturation indicator.

resistivity measurement

Measuring the formation's electrical resistance, the basis of estimating water saturation.

resistivity reading

The resistivity value a log records at a depth.

resistivity tool

The logging instrument measuring formation resistance to current.

resistivity, electrical resistivity

An intrinsic property that quantifies how strongly a given material opposes the flow of electric current.

resistor

A component specifically designed to increase and/or control the amount of resistance in a circuit, used to reduce current flow.

reskilling and upskilling

Training for a different role against deepening capability in the present one.

resolution

The size of the minimum step in input or output voltage or current in an analog I/O module.

resolution matched

Said of two or more logs processed to the same vertical resolution so their readings can be combined.

resolver

A feedback device typically used with a variable speed controller to monitor the position and speed of a shaft by generating sine waves as the shaft turns.

resource allocation

Directing money and people to the priorities rather than spreading them evenly.

resource levelling

Rescheduling to remove over-allocation of people or equipment.

resource nationalism

A state asserting greater control over, or a larger share of, its petroleum wealth.

resource negotiation

Negotiating internally for people, budget or equipment.

resource pool

The shared set of resources available across projects.

resources

All quantities of petroleum (recoverable and unrecoverable), naturally occurring, discovered and undiscovered, plus those quantities already produced. Resources include both discovered and undiscovered accumulations.

resources, hydrocarbon resources

Hydrocarbons which may or may not be produced in the future. A resource number may be assigned to an undrilled prospect or unappraised discovery. Appraisal by drilling additional delineation wells will confirm field size and may lead to project sanction, at which point the relevant government body issues a production license enabling development. This is also the point at which reserves can be formally booked.

respirator

Any device designed to protect the user from airborne contamination or to supply the user with a breathable gas in an oxygen-deficient atmosphere.

respirator fit

How well a respirator seals to the wearer's face, without which its rating means nothing.

respiratory protection

Equipment protecting the wearer from an unbreathable or contaminated atmosphere.

response curve

The plot of an instrument's output against its input.

response matched

Said of measurements whose responses to the formation have been made equivalent, in depth of investigation as well as resolution.

responsible ai

Developing and deploying models in a way that is transparent, accountable and consistent with legal and ethical obligations.

responsive design website

A site that adapts its layout to whatever screen it is viewed on.

restore

The process of downloading a project from a PC or an EEPROM to a PLC.

restored state core

A cleaned core plug resaturated with reservoir fluids and aged, to bring its wettability back toward the in-situ condition.

restraining spring

The spring opposing movement in a relay or valve, which sets its operating point.

restraint coil

A component that works to keep the contacts of a relay open.

restriction orifice

A fixed plate limiting flow permanently, cheaper and more reliable than a control valve.

results-based management

Managing toward defined outcomes rather than toward completion of activities.

resume tailoring

Rewriting a resume for each specific role rather than sending one version everywhere.

retail gasoline

Gasoline sold to the public at service stations.

retail outlet

The station or shop at which fuel is sold to the end consumer.

retain, divest or expand

The three standing choices for any asset, revisited as conditions change.

retaining nut

A nut that keeps a part in place.

retarder

A cement additive that delays setting so the slurry stays pumpable long enough to be placed.

retarders

Additives that slow cement setting so it can be placed before it hardens.

retention

A percentage of payment withheld until defects have been made good.

retention pond

A pond designed to capture contaminated rainwater runoff and keep it from getting into a nearby body of water or soaking into the ground.

retention time

The time a fluid element spends inside a vessel before leaving it.

retentive time-delay relay

A time-delay relay that retains the accumulated value of the delay when the timer rung goes false. When the rung goes true again, the timer starts timing where it left off. (Normal time-delay relays immediately reset the accumulated value to 0 when the timer rung goes false.)

retort

A distillation unit that boils off and condenses the liquids from a measured sample so its water, oil and solids fractions can be determined.

retort method

Determining core fluid saturations by heating the sample and measuring the water and oil driven off.

retort solids

The fraction of a mud not recovered as liquid in the retort, taken as its total solids content.

retort test

The API procedure that determines a mud's water, oil and solids content by distillation.

retrievable

Designed to be recovered from the well rather than left permanently.

retrievable bridge plug

A plug set to isolate the wellbore below it that can be unset and pulled once the work is finished.

retrievable gun

A perforating gun whose carrier survives the shot and is pulled back out of the well.

retrievable packer

A packer run and pulled on the same string, unset by string manipulation or pressure rather than milled out.

retrieval augmented generation (rag)

An architecture in which a language model retrieves relevant documents at query time and answers from them, abbreviated RAG.

retrieval system

The equipment (including a retrieval line, chest or full-body harness, wristlets, if appropriate, and a lifting device or anchor) used for non-entry rescue of persons from permit spaces.

retriever

The tool run to recover a plug or device from the well.

retrofitting

Modifying existing plant for a new duty, usually cheaper than new build and constrained by what is already there.

retrogradation

A stacking pattern in which successive beds step landward because sediment supply cannot keep pace with accommodation.

retrograde condensation

The dropping out of liquid in a gas reservoir as pressure falls below the dewpoint, the opposite of ordinary vaporization.

return

The instruction that directs PLC program control to return to the original program when a subroutine is terminated.

return activated sludge

Activated sludge that is returned from a clarifier to an aeration basin in a biological treatment system.

return on capital employed (ROCE)

ROCE is a measure of the profitability of a company's capital employed in its business compared with that of its peers. ROCE is calculated as a ratio, with the numerator of net income plus after-tax interest expense and the denominator of average total equity plus total debt. The net income is adjusted for nonoperational or special items impacts.

return on investment (ROI)

Gain relative to the amount invested, expressed as a percentage.

returns

The fluid coming back up the annulus and out of the flowline while circulating.

reverberation

Repeated energy from a strong interface, which obscures deeper reflections.

reverse acting

A type of controller setup in which an increase in the value of the input causes a decrease in the value of the output.

reverse bias

The bias potential that inhibits current flow across a P-N junction: a positive potential applied to the N-type material and a negative potential applied to the P-type material.

reverse biased

The bias potential that inhibits current flow across a P-N junction: a positive potential applied to the N-type material and a negative potential applied to the P-type material.

reverse buckling disc

A pressure relief device that ruptures when the disc is pushed outward by system pressure. Some reverse buckling discs have a knife point to puncture the disc or are scored.

reverse circulating valve

A downhole valve that opens a port between tubing and annulus so the string can be circulated out from the top down.

reverse circulation

Pumping down the annulus and taking returns up the string, the opposite of normal circulation.

reverse combustion

In-situ combustion in which the burn front moves toward the injection well, against the direction of the injected air.

reverse dial

An alignment method reading two dial indicators facing opposite ways to resolve offset and angle.

reverse drilling break

This slowing of drilling progress, while technically also a drilling break, is usually referred to as a "reverse drilling break", or simply "reverse break."

reverse fault

A dip-slip fault on which the hanging wall has moved up relative to the footwall, formed under compression.

reverse fault, thrust fault

A reverse, or thrust, fault is a geological fault in which the hanging wall has moved upwards relative to the footwall. Reverse faults occur where two blocks of rock are forced together by compression.

reverse flow

See Counterflow.

reverse logistics

Handling returns, repairs and end-of-life recovery back up the chain.

reverse resistance

Resistance across a reverse-biased P-N junction.

reversing out

Circulating down the annulus and up the string to bring the contents of the string to surface.

revision

Reworking a draft for structure and argument, as distinct from correcting it.

revision block

A portion of a title block that usually contains a general description of each revision, the revision number, and the date of the revision.

revision number

A number on a diagram that indicates the number of times a diagram has been revised.

reward system

How pay, promotion and recognition are structured, which drives behavior more than policy statements do.

reworking

Reworking is the mixing of various sediments in a fluvial environment.

RFx / Request for Proposal (RFP)

The formal invitation asking suppliers to propose against a defined scope.

rheologic

Describing flow and deformation behavior, including elasticity, plasticity and viscosity. In geology it governs how ice, salt, magma and rock move.

rheological

Pertaining to how a material deforms and flows — its viscosity, plasticity and elasticity.

rheological property

Any of the measured flow characteristics of a fluid — plastic viscosity, yield point and gel strengths.

rheology

Rheology is a branch of physics that deals with the deformation and flow of matter, especially the non-Newtonian flow of liquids and the plastic flow of solids.

rheology modifier

An additive for oil and synthetic muds that raises low-shear-rate viscosity without thickening the fluid at the bit.

rheostat

A rheostat is an electrical instrument used to control a current by varying the resistance.

rhine graben

The European rift valley, a textbook example of an extensional basin.

rhombohedral

The crystal form of calcite and dolomite, which governs how carbonates dissolve.

rhombohedral packing

The tightest regular arrangement of equal spheres, leaving about 26 percent of the volume as pore space.

ribbon mixer

A mixer that consists of two spiral-shaped impellers, called ribbons, inside a rectangular vessel.

rich amine

An amine solution that has absorbed acid gases (hydrogen sulfide and/or CO2).

rich gas

Natural gas carrying a substantial fraction of ethane and heavier components, as opposed to a lean, mostly methane gas.

rich gas condensate

A gas condensate that drops out a large volume of liquid below the dewpoint, often several hundred barrels per million cubic feet.

rich glycol

Glycol leaving the bottom of a dehydration contactor after it has absorbed water from the wet gas.

rich oil

A special oil used in gas processing when it is saturated with NGLs.

Rich-azimuth towed-streamer acquisition

Marine acquisition combining wide-azimuth geometry with sailing in several directions, so both offset and azimuth coverage are dense.

Ricker wavelet

A zero-phase, symmetric wavelet defined by a single dominant frequency, convolved with a reflectivity series to produce a synthetic seismogram.

rider

A type of motor-driven pallet jack that has a platform to allow the operator to stand on the jack as it is being used. Also called a walkie/rider.

rift

A zone where the crust is being pulled apart, dropping a block down between normal faults.

rift basin

A basin formed where crust is pulled apart, characteristically deep, narrow and fault-bounded.

rift system

A connected set of rift basins formed in one extensional episode.

rifting

Crustal extension that thins and drops the crust, forming many of the world's petroleum basins.

rig

The assembly of hoisting, rotating, circulating and power equipment used to drill a well.

rig count

The published tally of active rigs, watched as a leading indicator of future supply.

rig down

To dismantle equipment after a job and prepare it for removal from the wellsite.

rig floor

The working deck of the rig, at the top of the substructure, where the crew handles pipe.

rig spread cost

The rig spread cost is the total daily operating cost of an operating oil rig.

rig time

Time the rig is engaged, and the unit almost every drilling decision is costed in.

rig up

To make ready for use. Equipment must be moved onto the rig floor and assembled.

rigger

The person planning and directing a lift.

rigging

The planned movement of material, equipment, and loads from one place to another using ropes, chains, hoists, or other types of equipment.

rigging equipment

The slings, shackles and hooks used to make a lift.

rigging link

A type of rigging connector that typically has two holes.

right angle

A 90 angle.

right angle set

A slurry that stays thin and then thickens from about 30 to 100 Bc in a very short time.

right cylinder

A cylinder that has generating lines perpendicular to the bases, with its ends closed to form two circular surfaces.

right of first negotiation

A right to negotiate exclusively for a period before the seller may deal with others.

right of first offer

A right to receive the first opportunity to buy before the seller approaches the market.

right of first refusal

The right of other parties in a lease, well or unit to buy a selling party's interest on the same terms before a third party can.

right triangle

A triangle that has a 90 angle.

rigidity

Resistance to shear deformation, one of the elastic moduli controlling seismic velocity.

rigless operation

Well intervention performed without a rig over the well, leaving the tree and completion in place and working under pressure.

RIH

Run in hole: lowering pipe, a tool string or coiled tubing into the well in a controlled manner.

ring

A type of network topology that resembles a bus network with joined, rather than terminated, ends.

ring gasket

A type of gasket normally used with raised face flanges. A ring gasket covers only the raised portion of the flange, fitting within the ring of bolts/studs.

ring packing

Packing supplied as split rings stacked in a gland.

ring resistivity

A focused shallow resistivity measured by a ring electrode on a logging-while-drilling collar.

ring terminal

A crimp-on terminal that has a circular, ring-like tongue.

ring type joint

A joint constructed with a groove machined into the face of each flange that matches the groove in its companion flange. When the flange is tightened, a metal ring is used instead of a gasket to seal the flange. These types of joints are most commonly found in high pressure systems.

ring-fencing

Confining cost recovery and tax relief to a single license, so losses elsewhere cannot shelter its income.

ring-joint flange

A flange that has a raised area around the center opening with a flat-bottomed groove machined into the center of the raised area.

ringworm corrosion

A ring of corrosion a few inches below the upset on a tubular, where the metallurgy differs from the rest of the pipe.

ripple marks

Sedimentary structures which indicate agitation by water (either current or waves) or wind.

rise time

The time taken for a pulse or output voltage step to change from 10% to 90% of its maximum or final value. An oscilloscope cannot accurately display pulses with rise times faster than its own.

riser

The area of a cat cracker in which the cracking reaction takes place.

risers

Points on the commutator of a DC motor where the actual connections between the armature windings and the commutator segments are made.

rising stem

A valve stem that travels up out of the body as the valve opens, showing its position.

rising-bubble apparatus

A laboratory cell in which a gas bubble is watched rising through reservoir oil, its shape and disappearance indicating miscibility.

risk analysis

Examining a risk in enough detail to decide how to treat it.

risk and return

The principle that higher expected return is compensation for accepting more risk.

risk appetite

How much risk an organization is willing to accept in pursuit of its objectives.

risk assessment

Identifying risks and judging their likelihood and impact.

risk management (HR)

Identifying and controlling the people-related exposures that could cost the organization.

risk management framework

The structured process by which risk is identified, assessed, treated and monitored.

risk mitigation

Action taken to reduce a risk's likelihood or impact.

risk ranking

Placing risks in order of severity and likelihood so attention goes where it matters.

risk register

The maintained list of identified risks with their assessment, owner and mitigation.

risk tolerance

The acceptable variation around that appetite for a specific risk.

risked and unrisked value

Value before and after multiplying by the chance the project happens at all.

river delta

The sediment body built where a river enters standing water.

rivet

A fastener upset in place to join plates permanently.

RM

Rheology modifier — an oil mud additive that raises low-shear viscosity without raising plastic viscosity.

rms velocity

The root-mean-square velocity, the quantity stacking analysis actually measures.

RMS voltage

Root Mean Square voltage; the voltage displayed by an AC voltmeter, a value equal to 0.707 x Emax, where Emax is the maximum value of the AC voltage.

road box

A covered concrete or metal box giving access to a buried valve alongside a road.

road octane number

The average of the research octane number and the motor octane number [(R + M) ÷ 2]; the octane number given on gasoline pumps.

road-grade asphalts

Asphalts that are suitable for use in paving.

roadmap to change

The sequenced route from current state to intended state, with checkpoints.

roadmap to success

The sequenced plan of what must be achieved by when for a strategy to be realized.

robustness

The measure of a control loop's stability under all operating conditions.

rock

A rock is a naturally occurring solid aggregate of minerals, or mineraloids.

rock deformation

Change of shape or volume in rock under stress.

rock formation, formation

Rock formation refers to specific sedimentary strata, or other rock unit, in stratigraphic and petrologic studies.

rock fragment

A piece of pre-existing rock incorporated as a grain, which weakens the framework as it compacts.

rock matrix acidizing

Rock matrix acidizing involves injecting acid into the well, penetrating the rock pores at pressures below the fracture pressure. This stimulates the well to improve the hydrocarbon flow.

rock mechanics

The study of how rock deforms and fails under stress.

rock porosity

The fraction of rock volume that is void space.

rock properties

The physical characteristics of a reservoir rock — chiefly porosity and permeability — that let it hold and deliver fluids.

rock texture

The sizes and shapes of grains, the relationships between neighboring grains, and the orientation of grains within a rock.

rock texture, texture

Rock texture refers to the sizes and shapes of grains, the relationships between neighbouring grains and the orientation of grains within a rock.

rock types

A grouping of rocks sharing the same depositional and petrophysical characteristics.

Rockwell hardness number

A hardness value from the depth an indenter penetrates a metal under a set load, quoted with its scale letter.

Rockwell hardness testing

Hardness measurement from the depth a diamond cone or steel ball penetrates under a defined load.

rod elevators

Light elevators shaped to grip a sucker rod under its coupling for running and pulling the rod string.

rod end

The end of a rod, and where thread or eye connections fail.

rod load

The load carried by the rod string, which sets rod size and fatigue life.

rod pump

A downhole plunger pump driven from surface through a string of sucker rods, the original artificial lift method.

rod pumping

Artificial lift by reciprocating a downhole pump on rods, the most common method on land.

rod string

The assembled sucker rods and couplings that transmit surface stroke to the downhole pump.

rod unit

A light workover rig built for pulling and running rods and downhole pumps rather than tubing.

role delineation study

The research establishing what practitioners actually do, from which an exam's content is derived.

role play

An exercise where participants take defined parts and negotiate or decide in character.

role-playing

Learning by taking a part and acting the situation through.

roles and responsibilities

Who does what and who decides, agreed explicitly rather than assumed.

roll a tank

To circulate or inject through the roll line to stir a tank's contents into a uniform mixture.

roll line

A perforated pipe around the inside of a tank through which fluid is pumped to stir the contents.

roll-off

The roll-off frequency is the frequency above which a filter generates significant attenuation. Empirically this is regarded as the point where the amplitude is reduced by 3 dB, or the power by 6 dB.

roller bearing

A bearing carrying load on cylindrical rollers, suited to heavy radial loads.

roller cone bit

A bit whose cutting structure sits on two or three rotating cones that crush and gouge the rock as they turn.

roller stem

A slickline stem fitted with rollers so it runs through deviated tubing on rolling rather than sliding friction.

rolling aging test

A mud test in which the sample is tumbled at elevated temperature for a set period before its properties are measured.

rolling contact bearing

A bearing that uses balls or rollers to overcome friction. Can oppose radial or axial thrust, or a combination of the two. Also called an anti-friction bearing.

rollover

Rollover is the cumulative effect of downthrown thickening, slumping and rotation.

rollover anticlines, fault rollovers

Rollover anticlines and fault rollovers form when the hanging wall slumps into the low pressure extensional zone associated with listric normal faulting.

rollovers

Components on each end of a tank truck's spill dam that help prevent the tank from being punctured and valves and vents from being damaged if the truck rolls over.

RON

Research octane number; indicates gasoline performance under mild operating conditions.

roof drain

The drain removing rainwater from a tank roof.

root

The quantity that when multiplied by itself a specific number of times equals a given number.

root cause

The underlying failure whose correction would have prevented the incident.

root-mean-square velocity

The square root of the mean of the squared interval velocities, weighted by traveltime through each layer.

rootlet horizons

A rootlet horizon refers to the layer of soil (within a soil profile) where the majority of plant roots, particularly fine rootlets, are concentrated; commonly this is considered the topsoil layer where roots actively absorb nutrients and water from the soil.

rose diagram

A circular distribution plot of directional data (azimuth frequency), plotting lines at each of the 360 degrees of a compass distribution.

rotameter

A type of flow meter, consisting basically of a tapered tube and a float, that measures and indicates flow rate.

rotary

A circular or turning motion.

rotary air heater

An air heater that operates by rotating heated surfaces through the air being supplied to a boiler.

rotary bushing

The bushing set into the rotary table that transmits rotation to the kelly.

rotary drilling

Drilling by turning the bit on the end of the drillstring while circulating fluid to remove cuttings.

rotary hose

The large-bore flexible hose carrying mud from the standpipe to the swivel or top drive.

rotary motion

Movement in a circle about an axis.

rotary pump

A type of positive displacement pump containing screws, gears, or similar devices that move fluid with a rotary motion.

rotary sidewall core

A sidewall core sample acquired from the side of the borehole by using a diamond-tipped drill to mechanically cut individual plugs, which are then broken off and pulled from the borehole wall.

rotary sidewall coring

The rotary sidewall coring tool was developed to recover sidewall core samples without the shattering impact of the percussion system. Suitable for hard to friable rock, the rotary sidewall corer uses a diamond-tipped drill to cut individual plugs from the sidewall.

rotary sliding vane

A positive-displacement machine with vanes sliding in a rotor to sweep the working volume.

rotary steerable

A system steering the well while the whole string rotates continuously.

rotary steerable system

A directional tool that steers the bit while the whole drillstring keeps rotating, abbreviated RSS.

rotary table

The revolving or spinning section of the drill floor that provides power to turn the drill string in a clockwise direction. The rotary motion and power are transmitted through the kelly bushing and kelly to the drill string.

rotating blade

A blade on a rotor that does work on the fluid.

rotating control device

A pressure-containing head that seals around the drillstring while it rotates, diverting returns to a closed line.

rotating equipment

Pumps, compressors and turbines, the class needing alignment, lubrication and vibration monitoring.

rotating field generator

A type of AC generator in which direct current is fed to the rotor and the output voltage from the generator is taken directly from the stator coils.

rotating part

A component that turns in service.

rotating ring

The rotating half of a mechanical seal face.

rotating shaft

A shaft that turns in service.

rotating system

The rig components that turn the drillstring.

rotation

A circular or turning motion.

rotational gas lift

A closed gas-lift system in which produced gas is compressed and reinjected rather than taken to sales.

rotational slides

Rotational slides move along a surface of rupture that is curved and concave.

rotational viscometer

The instrument measuring viscosity from the torque on a rotating bob.

rotor

The movable or rotating part of a motor, pump, turbine, or AC generator. In a centrifugal pump, it usually includes the impeller, shaft, and all parts between the bearing housings and impeller.

rotor blade

The blade on a rotating element that does the work on the fluid.

rotor shaft

The rotating shaft carrying a machine's impellers or lobes, and where vibration is measured.

rotor winding

The winding on the rotating element of a machine.

roughneck

A roughneck is a drill floor hand, or member of the drilling crew, who works under the direction of the driller to make or break connections as drill pipe is tripped in or out of the hole.

round the shoulders

Round the shoulders refers to reducing the sharpness of the waveform peaks.

round thread

An API connection with a rounded thread profile that seals on thread compound rather than on metal contact.

round trip

The process of removing the entire drill string from the borehole (normally to replace a component such as the bit), followed by running it back down to the bottom. In metering, the movement of a displacer completely in one direction and back to the starting point.

roustabout

A general labourer on a rig or production site, handling maintenance, housekeeping and manual work.

route of exposure

The means by which material may gain access into the body, such as breathing, swallowing, or entering through the skin or eyes.

routes of entry

The means by which material may gain access into the body, for example, breathing, swallowing, or entering through the skin or eyes.

routine core analysis

The standard set of core measurements — porosity, permeability, grain density and fluid saturations.

routine inspection

A scheduled check made without taking equipment apart.

routing protocol

The protocol by which routers learn and share paths through a network.

ROV

Remotely operated vehicle: an unmanned submersible flown from a surface vessel on a tether, used for subsea installation, inspection and light intervention.

royalty

Payment made to the owner of oil or gas rights equal to a percentage of production ("in kind") or equivalent free of all costs.

royalty interest

A share of production or its revenue, free of the costs of drilling and operating.

RP

Recommended Practice — an API document setting out accepted procedure, as distinct from a Specification, which sets requirements.

RS-232

A PC communication standard for connecting two serial devices together.

RS-232 protocol

A standard communications protocol that governs the transmission of data through networks.

RS-485 protocol

A standard communications protocol that governs the transmission of data through networks.

RSLinx

Allen-Bradley's software for communicating between PLCs and PCs.

RSLogix

Allen-Bradley's PLC programming software.

RTD

Resistance Temperature Detector. A type of sensor that uses a resistor whose resistance is directly related to its temperature.

rubber glove

Insulating or chemical-resistant hand protection.

rubber tape

A splicing tape that is used to replace original insulation made of rubber. Also called latex tape.

rugose

Said of a borehole wall that is rough or irregular rather than smooth.

rugose borehole

A hole with an irregular wall, which degrades pad-contact log measurements.

rugosity

The roughness of the borehole wall, or the rapidity with which its diameter changes with depth.

rugosity, borehole rugosity

The roughness, unevenness, or irregularity of a borehole wall.

rule-based AI

Systems following explicitly written rules rather than learning from data.

run

In electrical work, a continuous installation of conduit from start to termination. In quality control, a pattern of instability on a control chart with a group of data points above or below the centerline. In oil production, the volume of crude oil sold or transferred from a lease tank to pipeline or tank truck.

run in hole

To lower a string or tool assembly into the well, abbreviated RIH.

rundown tank

A tank that receives a product or a blend component from a process unit and provides intermediate storage.

rundown tanks

Storage tanks that receive blend components from process units.

rung

The horizontal lines and the devices connected by them that make up a "row" on a ladder diagram.

running squeeze

A squeeze in which slurry is pumped continuously until the target pressure is reached.

running tool

The tool that carries a device downhole, sets it and releases from it.

runout

Deviation of a rotating surface from true, measured to judge shaft and coupling condition.

runout test

A procedure for determining if a pump shaft is bent or out of round.

rupture disc

A fail-safe pressure relief device made of metal that is designed to burst at a preset pressure, protecting equipment from excessive pressure.

rupture discs

Protective devices that are designed to break when pressure inside the exhaust hood rises above atmospheric pressure.

rupture disk

A disk installed in a flange fitting that ruptures when pressure becomes too great; another type of relief device.

ruptured disc

A burst rupture disc, which must be replaced before the equipment can be repressured.