Discover the IHRDC Energy Glossary_beta

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O

O-ring

A circular elastomer seal of round cross-section, seated in a groove and compressed between two surfaces to close a leak path.

OA

A designation for a self-cooled power transformer; abbreviation for "oil to air."

OA/FA

A designation for a self-cooled/forced air-cooled power transformer; abbreviation for "oil to air/forced air."

OBC

Ocean bottom cable: geophones and hydrophones on a cable laid on the seafloor, recording to a vessel and giving repeatable receiver positions.

object library

The icons that graphical software tools made available for building programs.

object-oriented vs. procedural programming

Organizing code around objects and their behavior against organizing it around sequences of steps.

objective criteria

Measures neither party controls, used to justify a term rather than assert it.

objectivity

Objectivity is the quality, or character, of being objective: lack of favoritism toward one side or another.

OBR

Oil/brine ratio — the proportion of oil to brine in the liquid phase of an oil mud.

observation [evidence]

Employees are directly observed doing their jobs.

observer

The member of a seismic field crew who runs the recording instruments and directs acquisition from the recording truck.

Occam's inversion

An inversion that fits electromagnetic sounding data with the smoothest model consistent with them, rather than with the closest-fitting model.

As it applies to bloodborne pathogens, reasonably anticipated skin, eye, mucous membrane or parenteral (such as piercing of the skin) contact with blood or other potentially infectious materials that may result from the performance of an employee's duties.

Occupational Safety and Health Administration (OSHA)

The United States regulator of workplace safety.

occupational safety law

The statutory framework requiring employers to provide a safe workplace.

occupational safety versus process safety

Preventing harm to individuals against preventing loss of containment, which need different controls.

ocean basin

A deep basin floored by oceanic crust.

ocean-bottom cable

A cable of geophones and hydrophones laid on the seafloor to record seismic data and relay it to a vessel, abbreviated OBC.

oceana (project economics simulation)

The petroleum economics simulation, building and defending a financial model for a field near Indonesia.

oceanic crust

Thin dense crust made at spreading ridges, too young and too hot to host most petroleum systems.

OCMA

The Oil Company Materials Association, a now-defunct body whose material specifications are still cited.

octahedral

The coordination geometry in clay mineral sheets, which governs their swelling.

octahedral layer

A sheet of aluminum or magnesium ions each surrounded by six oxygens or hydroxyls, forming one of the two building layers of clay minerals.

octahedral sheet

The alumina layer in clay structure, paired with tetrahedral sheets.

octal numbering system

The numbering system based on powers of eight.

octane

A number or rating that measures a fuel's anti-knock properties. Also, a paraffin hydrocarbon that is a liquid at atmospheric conditions.

octane gasoline

Gasoline classified by its octane rating.

octane giveaway

Deliberately blending a product to obtain an octane number that is above spec.

octane number

A measure of the antiknock properties of a gasoline.

octane pool

The octane numbers and the quantities of all of the gasoline blend components available within a refinery.

octane rating

A general indication of a gasoline's quality; a measure of how resistant a gasoline is to engine knock.

octanol

An eight-carbon alcohol; the iso- form is used as a defoamer in water-base muds.

octyl alcohol

Another name for octanol, the eight-carbon alcohol used as a mud defoamer.

OD

Outside diameter; the length of a straight line that passes from one side on the outside surface of a pipe, through the center of the pipe to the other side of the outside surface of the pipe.

odorless

Having no smell, which for hydrogen removes the leak warning that odorized natural gas provides.

off-delay time delay relay

A time delay relay in which the delay starts when the coil is de-energized, or turned off.

off-pattern well

A producer or injector displaced from the regular geometry of the injection pattern around it.

off-taker

The buyer committed to purchasing the output, whose creditworthiness underpins the financing.

offer and acceptance

The matched proposal and assent that create a contract.

offline

A state in which a PC or programming terminal is used to display, create, or edit a PLC program stored in its own memory. Also, a field communicator or laptop function that enables configuration data to be uploaded from and downloaded to smart field devices or a DCS.

offline and online assets

The materials and presence supporting a professional reputation in each sphere.

offloading

Discharging cargo from a vessel to shore or to another vessel.

offloading system

The equipment transferring cargo from a floating facility to a shuttle tanker.

offset

The error remaining after proportional control has stabilized a process variable following an upset; the difference between the final steady-state condition and the original set point value.

offset fitting

A type of fitting that is used to change the level of a conduit run.

offset vertical seismic profile

A vertical seismic profile acquired with the source offset from the rig rather than beside it.

offset voltage

A voltage that is introduced at the input of an op amp in order to produce an output of exactly zero volts.

offset VSP

A vertical seismic profile recorded with the source set some distance from the wellhead, so the raypaths sample away from the borehole.

offset well

A nearby existing well whose records are used to plan a proposed well.

offset well location

A potential drill location adjacent to an existing well.

offset wells

An existing wellbore close or adjacent to a planned well, often used as a source of local geological and reservoir information, pressure regimes, and other data helpful to planning and executing the drilling of the proposed well.

offshore development

A development requiring platforms or subsea equipment and marine logistics.

offshore drilling

Drilling at sea, from a fixed, jackup or floating unit.

offshore field

A producing field located at sea.

offshore pipeline

A pipeline laid on or beneath the seabed.

offshore platform

The fixed or floating structure carrying wells and process equipment at sea.

offshore procurement

Buying from suppliers abroad.

offshore rig

A drilling unit operating at sea.

offshore wind

Wind generation sited at sea, where wind is stronger and steadier but installation and access cost more.

offshoring

Moving activity to another country, usually for cost.

offtake contract

The agreement committing a buyer to take a project's output, without which financing is unlikely.

OGMP 2.0 (Oil and Gas Methane Partnership)

The United Nations-backed framework for measurement-based methane emissions reporting.

ohm

The unit of measurement of electrical resistance. One ohm is defined as the resistance that allows one ampere of current flow in a circuit with a source voltage of one volt. The Greek letter omega (Ω) is typically used as an abbreviation.

ohm law

The relation making current proportional to voltage and inverse to resistance.

Ohm's law

The definite relationship between voltage, current, and resistance in an electrical circuit, stating that current equals voltage divided by resistance (I = E/R). Electric current is directly proportional to voltage and inversely proportional to resistance.

oil absorption

Recovering heavier hydrocarbons from gas by contacting it with a lean absorption oil.

oil allowable

The regulated volume of oil which can be produced over a designated period of time.

oil and gas accounting methods

The choice between successful efforts and full cost, which changes reported profit and asset value.

oil and gas lease

A contract by which a mineral owner grants a company the right to explore for and produce hydrocarbons on the owner's land.

oil and gas separator

A pressure vessel that splits the wellstream into a gas stream and a total liquid stream.

oil assay

The laboratory workup showing what products and yields a crude will give.

oil bank

A zone of raised oil saturation built up ahead of an injected fluid as it sweeps oil through the reservoir.

oil base drilling mud

An oil base drilling mud is an invert-emulsion mud, or an emulsion whose continuous phase is oil.

oil base mud

An invert-emulsion drilling mud whose continuous phase is oil.

oil circuit breaker

A breaker interrupting the arc under insulating oil.

oil content

The volume percentage of oil in a drilling mud, measured by retort distillation.

oil cooler

An exchanger removing heat from lubricating oil.

oil droplet

A discrete drop of oil dispersed in water.

oil dump valve

Automatic valve discharging separated oil on level.

oil field

An area underlain by one or more oil accumulations, treated as a single unit for development.

oil field emulsion

Water and oil mixed and stabilized at the wellsite, the form most production arrives in.

oil filtrate

The liquid phase of an oil-based mud that invades the formation.

oil fluorescence

Fluorescence that derives largely from the aromatic hydrocarbon fraction of oil. The emission is strongly influenced by the chemical composition (e.g., fluorophore and quencher concentrations) and physical characteristics (e.g., viscosity and optical density) of the oil.

oil formation volume factor

The volume a barrel of stock tank oil occupies in the reservoir, including the gas dissolved in it.

oil import

Crude or product brought into a country from abroad.

oil kitchen

The part of a basin where a source rock sits within the oil window and is actively generating liquid hydrocarbons.

oil measurement

Quantifying oil for custody, corrected for temperature, pressure and water content.

oil mining

Surface mining of shallow oil sand, which is then processed at a plant to separate the bitumen from the sand.

Oil Mining Lease (OML)

The pre-Act instrument granting the right to produce, now converted to a petroleum mining lease.

oil mud

A drilling fluid whose continuous external phase is oil — diesel, mineral oil or a synthetic.

oil on cuttings

The quantity of oil clinging to drilled cuttings, measured in grams per kilogram of dry solids.

oil or gas show

A visual observation of hydrocarbons, typically observed as florescence on wellbore cuttings when viewed with ultraviolet light (indicating oil) or increased gas readings from the mud logger's gas-detection equipment (indicating gas).

oil outlet

The vessel connection oil leaves by, set above the water draw.

oil pipeline

The pipe system transporting crude or products.

oil pool

A single continuous accumulation of oil in the subsurface, one or more of which make up a field.

oil price forecasting

Projecting future prices for planning, knowing the forecast will be wrong and planning for a range.

oil prone

Said of a source rock whose kerogen is more likely to generate oil than gas on maturation.

Oil Prospecting Licence (OPL)

The pre-Act exploration instrument, now converted to a petroleum prospecting license.

oil recovery eor

Enhanced oil recovery, methods freeing oil that pressure maintenance leaves behind.

oil refinery

The plant converting crude into saleable products.

oil refining

Separating and converting crude into products, and today one of the largest consumers of hydrogen.

oil reservoir

A reservoir whose hydrocarbons are predominantly liquid.

oil sand

A sand or sandstone whose pore space is filled with oil, in current usage particularly one holding immobile bitumen.

oil sands

Geologic formation comprised predominantly of sand grains and bitumen, a highly viscous form of crude oil.

oil sands or tar sands

Sandstone deposits that are highly saturated with natural bitumen.

oil saturation

The fraction of pore space occupied by oil.

oil separator

Vessel recovering lubricating oil carried over from a compressor's discharge.

oil shale

Shale rich in immature kerogen, which yields oil only if heated artificially.

oil shales

Shale, siltstone, and marl deposits that are highly saturated with kerogen.

oil shrinkage

The volume a reservoir oil loses when its dissolved gas comes out at surface.

oil spill

An uncontained release of oil to the environment.

oil swelling

The increase in oil volume that occurs when injected gas or solvent dissolves into it.

oil tanker

The ship carrying crude or products in bulk.

oil viscosity

Oil's resistance to shear, which sets film thickness and therefore whether bearings survive.

oil well

A well whose principal commercial product is oil rather than gas.

oil wiper

The element wiping oil from a moving rod.

oil-emulsion mud

A water-base mud with oil emulsified into it as a dispersed internal phase, typically 5 to 10 percent by volume.

oil-in-water emulsion

An emulsion in which oil droplets are dispersed through a continuous water phase.

oil-indexed gas pricing

Pricing gas by formula against crude, a convention predating liquid gas markets.

oil-insulated shunt reactor

A reactor immersed in oil, connected across the line to absorb reactive power.

oil-mud emulsifier

The surfactant that holds brine droplets dispersed in the oil phase of an invert-emulsion mud.

oil-water contact

The level in a reservoir above which oil predominates and below which water predominates.

oil-water interface

The surface separating an oil layer from a water layer, in a reservoir or in a vessel.

oil-wet

The preference of a solid surface to be in contact with an oil phase rather than a water or gas phase. Wettability is the tendency of one fluid to spread on, or adhere to, a solid surface in the presence of other immiscible fluids.

oil/brine ratio

The proportion of oil to brine in the liquid phase of an oil mud, each as a percentage of total liquid.

oil/water ratio

The ratio of oil to water in the liquid phase of an oil mud, each as a percentage of the total liquid.

oiler

The crew member responsible for lubricating and maintaining machinery.

oilfield battery

An electrochemical cell supplying power to a downhole or surface tool, built to survive well temperatures.

oilfield service agreement

A contract for a defined technical service such as seismic, cementing or wireline.

oilfield service company

A contractor supplying drilling, seismic, completion or equipment services to operators.

OJT checklist

A document that identifies the on-the-job training (OJT) steps that a trainee must follow to accomplish a performance objective.

olefin

A hydrocarbon with carbon atoms connected in a straight chain, two of which are linked by a double bond. A high-octane, unstable component of the light ends produced in a cat cracking unit that is reacted with isobutane in the alkylation process.

olefinic hydrocarbon

An unsaturated hydrocarbon with at least one carbon-carbon double bond, also called an alkene.

olefins

Highly reactive, unsaturated hydrocarbons that can be used in alkylation units to produce high-octane gasoline and as petro-chemical feedstocks.

oligomer

A short polymer of only a few monomer units, typically two to five.

omni-directional

Responding equally in all directions.

on stream

In production and delivering to market.

on-delay time delay relay

A time delay relay in which the delay starts when the coil is energized, or turned on.

on-the-job training (OJT)

Formal, structured training for acquiring the skills and knowledge to perform a job that takes place in the actual work environment.

on/off control

A control algorithm that causes an output signal to be either on or off.

onboarding

The structured first period that turns a hire into a productive, retained employee.

onboarding plan

The scheduled activities, contacts and milestones for a new hire's first months.

onboarding remotely

Integrating a new hire who never physically enters the workplace.

once-through boiler

A boiler in which water goes through only once without recirculating.

once-through system

A type of circulating water system in which the water from a large source, such as a lake, flows through the system one time and is returned to the source.

one-dimensional (1D) seismic data

A check-shot or vertical seismic profile at a single well, giving traveltime against depth on one vertical line.

one-hole panelboard connector

A mechanical connector that is designed for terminating a circuit at a panelboard or breaker box.

one-slot addressing

An I/O addressing scheme where each slot in the I/O rack is defined as a 16-bit group.

one-time fuse

A fuse that is discarded after it has blown.

one-way time

The traveltime from surface to a given depth in one direction only, as measured by a check-shot survey or VSP.

onlap

The termination of gently dipping younger beds against a more steeply dipping older surface.

onlapping

Terminating landward against an underlying slope, the pattern of a transgressive sequence.

online

The state in which the PC or other programming terminal is used to display, create or edit a PLC program while the program resides in the PLCs memory.

online learning accessibility

Designing so learners with disabilities can use the material without barriers.

online programming

The process of modifying a PLC program while the processor is in the "Run" mode.

onshore

On land, as opposed to offshore.

onshore development

A field development on land, where costs and logistics differ sharply from offshore.

onshore exploration

Exploration conducted on land.

onsite

At the location itself rather than remote.

OOC

Oil on cuttings — the mass of oil retained per unit mass of dry cuttings, in grams per kilogram.

ooid

A small spherical carbonate grain with concentric coats, forming in agitated shallow water.

ooip

Original oil in place, the total volume in the reservoir before production.

oolitic

Made of ooids, small concentric carbonate grains, and typically well sorted and porous.

opacity

A measure of the lack of penetration of light through a substance.

opacity meter

An instrument that measures the concentration of suspended particles in a gas.

OPEC (Organization of the Petroleum Exporting Countries)

OPEC together with allied non-member producers, chiefly Russia, coordinating supply since 2016.

opec country

A member of the Organization of the Petroleum Exporting Countries.

opec member

A country belonging to the Organization of the Petroleum Exporting Countries.

open

A break that stops current flow in an electrical circuit; a circuit in which resistance is so great that there is no current flow.

open borehole

The uncased section of the well.

open circuit

A break in an electrical conductor or a circuit with resistance so great that there is no current flow. Can occur when fault current is not high enough to trip circuit breakers or blow fuses.

open flow potential

The rate a well would produce against zero flowing bottomhole pressure — the theoretical maximum with no restriction.

open heater

A heater in which condensate or feedwater is mixed together with steam.

open hole

Open hole is the uncased portion of a well.

open impeller

An impeller whose vanes are not enclosed by shrouds.

open loop gain

The designed gain of an op amp; the gain listed on op amp data sheets.

open perforation

A perforation that is clear and flowing, as against one plugged by debris.

open radial fan

A type of radial blade fan in which the blades are not enclosed; used for extremely abrasive service and for material handling.

open season

The process whereby the developer of a greenfield UGS facility or the owner/operator of an existing UGS facility solicits the interest of customers regarding a commitment to and pricing of various gas storage services.

open software

Software that is designed to run on standard computer platforms independently of proprietary equipment. Some open software can share information with other open programs.

open source

Software whose source code is published under a license allowing anyone to inspect, modify and redistribute it.

open system (network)

A system that is not proprietary, but rather uses a standard made available to many vendors. Some examples are PROFIBUS and TCP/IP.

open vs. closed systems

Systems that exchange with their environment against those that do not.

open-loop transresistance

In a transimpedance or current feedback amplifier, it is the ratio of change in dc output voltage to the change in dc current at the inverting input.

open-loop voltage gain

The ratio of change in output voltage to the change in voltage across the input terminals. Usually the dc value and a graph showing the frequency dependence are shown in the data sheet.

openhole completion

A completion in which the reservoir interval is left uncased, so fluids enter the wellbore directly from the rock.

openhole gravel pack

A gravel pack placed against an uncased producing interval, with the screen packed off directly in the open hole.

openhole log

A measurement recorded before casing is run.

openhole packer

A heavy-duty packer whose element seals against bare rock rather than casing.

openhole test

A drillstem test run in an uncased interval, with the tool sealed against the borehole wall by a packer.

opening bomb

A weighted plug dropped down the casing to shift the sleeve of a stage collar and open it for the second stage of cement.

opening gauge

Measurement of oil level in lease tank prior to a transfer or run. May be called top gauge.

opening position

The terms first put on the table, which anchor the discussion that follows.

operability

How readily a plant can actually be run and kept within limits, as distinct from its design capacity.

operating agreement

The contract among working interest owners in a well or block, setting out what the operator does and what the nonoperators pay.

operating budget

The budget for day-to-day revenue and expense.

operating characteristic

How a device behaves across its operating range.

operating coil

The conducting coil of a magnetic contactor or relay that becomes an electromagnet when current flows through it, working to close contacts.

operating gas-lift valve (OGLV)

The lowest valve in a gas-lift string, the one lift gas enters through in normal production, abbreviated OGLV.

operating instruction

The written direction for running equipment.

operating interest

The working interest, which carries the right to develop the leased acreage and the obligation to pay its share of the costs.

operating parameter

A variable the equipment is run by, such as pressure, temperature or rate.

operating radius

The horizontal distance from the centerline of a crane's rotation to the center of the vertical hoist line or load block, measured with the load freely suspended.

operating temperature

Temperature over which the op-amp may be operated. Some of the other parameters may change with temperature, leading to degraded operation at temperature extremes.

operating valve

The gas lift valve actually injecting at the current conditions, the others being unloading valves.

operating voltage

The voltage equipment is designed to run at.

operation geologist

The geologist at the wellsite calling formation tops and sampling as the well is drilled.

operational amplifier

A high-gain, DC amplifier that can be configured to perform many functions. Commonly called an op amp.

operational and production planning

Translating strategic targets into rates, schedules and budgets at asset level.

operational integrity

Keeping equipment and procedures in a condition where containment and safety are assured.

operational readiness

The state of having people, procedures and systems in place before a facility starts up.

operational technology (OT)

The control systems that run physical plant, where availability matters more than confidentiality.

operations strategy

How operations will be configured to deliver the business strategy.

operator

The entity responsible for managing operations in a field or undeveloped acreage position.

operator interface

The equipment a machine or process operator uses to monitor and control the machine or process.

operator pumper

The field operator responsible for the wells and surface equipment on a lease.

OPEX (operating expenditure)

The recurring cost of running a facility once built.

OPITO

The Offshore Petroleum Industry Training Organization is an industry-owned skills body for the energy industry, offering a range of services and products to meet international skills needs and support workforce development.

opportunity statement

The short framing of an investment prospect that opens a simulation.

opposed blade damper

A type of damper that operates with alternate blades turning in opposite directions.

optical analyzers

Analyzers that determine properties of materials by measuring the interactivity of electromagnetic radiation with matter.

optical index

A measure of how much light an optical probe receives back from the fluid at its tip, used to distinguish gas, oil and water.

optical probe

A production logging sensor that identifies the fluid at its tip from how light is reflected at the probe face.

optimal development plan

The chosen combination of wells, facilities and phasing that maximizes value.

option

The right, without the obligation, to buy or sell at an agreed price.

optionality

The value in having a choice — of grade, timing or destination — that need not be exercised.

OR gate

A digital logic gate that produces a HIGH output (1) if one or more of its inputs are HIGH (1). If neither input is HIGH, the output is LOW (0).

orchestration

Coordinating several models, services or data pipelines so they run together as one workflow.

organic acid

A weak acid such as acetic or formic acid used to stimulate a well where mineral acid would be too aggressive.

organic chemistry

The branch of chemistry dealing with compounds that contain carbon.

organic deposit

Damage caused by heavy hydrocarbons — paraffin wax or asphaltene — dropping out of solution as pressure or temperature falls.

organic geochemistry

The study of organic matter in rock, which establishes source potential and maturity.

organic material

Material composed of carbon based molecules.

organic peroxide

An organic compound that contains the bivalent -O-O- structure and which may be considered to be a structural derivative of hydrogen peroxide where one or both of the hydrogen atoms has been replaced by an organic radical.

organic solids

Solids composed of living or formerly living matter, such as fish and plant material.

organizational change

Any deliberate alteration to structure, process, technology or culture.

organizational climate

How it currently feels to work somewhere, which leaders can change faster than they can change culture.

organizational climate survey

The instrument measuring that, giving a baseline against which action can be judged.

organizational culture

The shared assumptions and habits that persist regardless of what policy says.

organizational design

Arranging structure, processes, rewards and people so the organization can execute its strategy.

organizational structure

How reporting lines, functions and decision rights are arranged.

organophilic

Said of a material treated so that it associates with oil and rejects water.

organophilic clay

Clay whose surfaces have been chemically coated so that it disperses in oil, used to viscosify an oil-base mud.

organophilic lignite

Lignite treated with a chemical that makes it oil-dispersible, used for filtration control in an oil-base mud.

orientation

The first introduction to the organization, its rules and its people.

orientation data

Orientation data shows where the dipmeter tool is located downhole with respect to vertical and geographic coordinates.

orienting

Setting a tool's rotational position, as for directional drilling or perforating.

orifice

A calibrated restriction across which pressure drop is measured to infer flow rate.

orifice fitting

A device designed to hold an orifice plate in a meter tube.

orifice flow constant (C')

Pronounced C-Prime. Part of the flow rate formulas. Consists of eleven factors which affect orifice flow rates.

orifice meter

An instrument used to measure the flow of fluids in a pipe.

orifice plate

A flat metal plate with a carefully machined circular, square-edged or beveled-edge hole, inserted in a pipeline to create a differential pressure that can be measured and converted to an indication of flow. Can also be used for pulsation control or pressure drops to create a sidestream.

orifice plate size

The bore of the plate, chosen so the differential falls in the middle of the recorder's range.

orifice size

The bore of the orifice plate, which sets the differential produced at a given flow.

orifice valve

A valve containing a fixed restriction that meters flow through it rather than shutting it off.

origin of installation

A reference to the main service drop bringing power into a plant.

original depositional

Relating to the condition at the time of deposition, before later alteration.

original drawings

Drawings created by a drafting person based on notes and sketches provided by the architect or engineer who designed the project.

orogenic

Pertaining to mountain building — the intense deformation that occurs where lithospheric plates converge.

orogeny

Orogeny is the tectonic process in which a section of Earth's crust is folded and deformed by lateral compression to form a mountain range.

orthographic projection

A type of drawing, sometimes called a Multiview projection, in which different views of the same object are shown.

orthorhombic

A symmetry class describing rock with three distinct principal directions.

oscillating

Moving back and forth about a mean position.

oscillation

Repeated variation about a mean, in pressure, flow or a wave.

oscillator

A device or circuit that converts a constant power into a fluctuating current or signal.

oscilloscope

A device for viewing oscillations by displaying them on a screen.

OSHA

Occupational Safety and Health Administration.

OSHA National Emphasis Program (NEP)

A targeted United States inspection campaign focused on a specific high-hazard industry.

OSHA standard

A specific mandatory workplace safety requirement issued by that agency.

OSI reference model

The seven-layer model describing how network functions stack.

osmosis

The movement of water through a semipermeable membrane from the less saline side toward the more saline side.

osmotic

Driven by a difference in salinity, which moves water into or out of shale.

osmotic pressure

The pressure that must be applied to the less saline side of a membrane to stop water crossing into the more saline side.

OSPAR

The Oslo and Paris Convention and its commission, which set marine environmental obligations for the North East Atlantic, including offshore decommissioning.

ostracod

A small bivalved crustacean whose shells date and correlate non-marine and marginal strata.

other potentially infectious materials

(1) The following human body fluids: semen, vaginal secretions, cerebrospinal fluid, synovial fluid, pleural fluid, pericardial fluid, peritoneal fluid, amniotic fluid, saliva in dental procedures, any body fluid that is visibly contaminated with blood, and all body fluids in situations where it is difficult or impossible to differentiate between body fluids; (2) Any unfixed tissue or organ (other than intact skin) from a human (living or dead); and (3) HIV-containing cell or tissue cultures, organ cultures, and HIV- or HBV-containing culture medium or other solutions; and blood, organs, or other tissues from experimental animals infected with HIV or HBV.

out of phase

A situation in which the voltages at the top or bottom of the primary and secondary windings on a transformer are of opposite polarity.

outage

A measurement taken from the surface of a liquid to a reference point at the top of the container. Also, a space for expansion created in a sample cylinder by bleeding displacement fluid, required for safe handling of NGL samples.

outboard

Away from the driver, said of the bearing furthest from the coupling.

outboard feet

The reading taken at the far end from the coupling during alignment.

outbound logistics

Moving finished goods out to customers.

outcrop

Rock exposed at the Earth's surface, where it can be examined and sampled directly.

outer boundary

The far edge of the modelled reservoir, whose assumed condition governs late-time pressure behavior.

outer casing

The outermost pressure-containing shell of a machine.

outermost shell

The outer electron shell, whose occupancy decides how an element bonds.

outlet damper

A damper that is located on the outlet side of a fan and used to control the air flow out of the fan.

outlet gas

Gas leaving a vessel or unit, having met whatever the unit was there to achieve.

outlet line

The line leaving a unit.

outlet nozzle

The vessel connection fluid leaves through, positioned to avoid drawing the wrong phase.

outlet separator

Separator on a unit's outlet, catching whatever the unit failed to remove.

outlet temperature

The temperature of the stream leaving a unit.

outlet valve

The valve on an outlet.

outlet water

Water leaving a unit, carrying whatever heat or contaminant it picked up.

outliers

A plotted data point that falls outside of a control limit on a control chart.

outlying data

Outlying data is data that lies an abnormal distance from other values in a random sample from a population.

output

Data provided by an EFC or other instrument.

output current

The amount of current that is drawn from the op-amp output. Usually specified as an absolute maximum rating, not for long term operation at the specified level.

output device

A device that acts as a load connected to an output module in a PLC.

output image table

Output Image Table The part of data memory in which the current states of the real outputs are stored.

output impedance

The frequency dependent small-signal impedance that is placed in series with an ideal amplifier and the output terminal.

output instruction

The programmable controller instruction setting an output.

output resistance

The dc resistance that is placed in series with an ideal amplifier and the output terminal.

output voltage

The voltage a device delivers, as distinct from what it was supplied.

output waveform

The wavelet actually produced by the source.

outright exposure

Exposure to the flat price level itself, rather than to a differential between two prices.

outside diameter

The measurement across the outside of a tubular, abbreviated OD.

outside micrometer

A micrometer used for measuring outside dimensions; the reading is taken between a fixed anvil and a movable spindle.

outsourcing

Contracting a function to an external provider rather than performing it internally.

oval gear

A positive-displacement meter using meshing oval rotors, each rotation passing a fixed volume.

oval gear meter

A type of flow meter that uses gears to trap and measure specific quantities of liquid.

ovality limit

The maximum out-of-round distortion allowed in a coiled tubing string before it is retired.

over travel

The condition in which the downhole pump plunger strokes further than the polished rod does at surface.

overall extended height

The distance from the floor to the highest point on a forklift when the mast and the forks are fully raised.

overbalance

Overbalance is the amount of pressure (or force per unit area) in the wellbore that exceeds the pressure of fluids in the formation.

overbalanced

Drilled with wellbore pressure above formation pressure, the conventional condition.

overburden

The rock and sediment lying above a point of interest, and the vertical stress its weight imposes there.

overburden pressure

Overburden pressure, also termed lithostatic pressure, confining pressure or vertical stress, is the pressure or stress imposed on a layer of soil or rock by the weight of overlying material.

overburden stress

The vertical stress from the weight of overlying rock.

overcracking

Cracking hydrocarbon chains beyond the desired degree.

overcurrent

Current above the rated value, which protective devices exist to interrupt before insulation burns.

overcurrent condition

Current above the rated value.

overcurrent protection

Protection achieved by de-energizing a circuit whenever the current exceeds a predetermined value, using devices such as fuses, circuit breakers, and magnetic relays.

overcurrent relay

A relay designed to operate when current is higher than desirable in part of a transmission and distribution system.

overcurrent unit

The element of a protective relay responding to excess current.

overdetermined system

An overdetermined system is the situation when there are more equations than the number of unknowns.

overfill

The situation created when a storage tank is filled to a specified level that is usually close to the tank's rated capacity.

overflush

Fluid pumped behind an acid treatment to push spent acid and reaction products away from the wellbore.

overfractionation

A condition that results in the excessive use of steam and other utilities to produce products.

overgrowth

Mineral grown onto an existing grain, which cements the rock and closes pore throats.

overhead condenser

The exchanger condensing a column's overhead vapor.

overhead guard

A forklift component that protects the forklift operator from falling objects.

overhead product

The product that is condensed from the vapor that flows out of the top of a distillation column.

overhead product flow

The rate of product drawn from a column's overhead.

overhead receiver

The vessel collecting condensed overhead from a column.

overhead system

The condenser, receiver and reflux equipment handling a column's overhead.

overhead vapor

The vapor leaving the top of a column.

overheat

Rise above safe temperature, which damages insulation, lubricant and metal in that order.

overlain

Covered by a younger unit above.

overload contact

The contact opening when a motor draws sustained excess current.

overload device

A device inside a motor controller that senses excessive levels of current and operates to create a break in the motor circuit.

overloading

A condition in which the vapor rising up a column is impeded by the liquid flowing down the column.

overmature

Said of a source rock heated beyond the oil window, having generated all it can and now yielding only dry gas or nothing.

overpressure

A condition when fluid pressure in a formation is higher than estimated from the normal hydrostatic fluid gradient for a given depth. Overpressure is a drilling hazard responsible for many well blowouts.

overpressured

At formation pressure above the normal hydrostatic gradient, a principal drilling hazard.

overpressured formation

An overpressured formation is when a fluid pressure is higher than estimated from the normal hydrostatic fluid gradient for a given depth.

overpressured zone

An interval at pressure above the normal gradient, requiring careful mud weight control.

overpressuring

Taking equipment above its rated pressure, which relief devices exist to prevent.

overpull

Tension applied above string weight when attempting to free stuck pipe.

override control

A control function that bypasses normal control algorithms or parameters in order to maintain safe or acceptable system operation when certain conditions occur.

overriding royalty

A share of production carved out of the working interest, free of drilling and operating costs but ending with the lease.

overriding royalty interest

A royalty carved out of the working interest by the lessee, free of production cost and expiring with the lease, abbreviated ORRI.

overshoot

The distance that a process variable passes the set point when the control loop responds to error.

overshoot factor

The ratio of the largest deviation of the output voltage from its final steady-state value to the absolute value of the step after a step change at the output.

overshot

An overshot is a downhole tool used in fishing operations to engage on the outside surface of a wireline tool. A grapple on the overshot grips the fish, allowing application of tensile force and jarring action. If the fish cannot be removed, a release system within the overshot allows the overshot to be disengaged and retrieved.

oversight

Monitoring delegated work closely enough to catch problems without taking the work back.

overspeed

A mechanical condition that occurs when rotating machinery, such as a turbine, exceeds its designed operating speed.

overspeed governor

A protective device that automatically energizes trip circuits to trip the turbine valves and stop steam flow to a turbine during an overspeed condition.

overthrust

A low-angle thrust fault along which one block has been carried a long distance over another.

overthrust block

An overthrust block is pushed by compressional forces over the offsetting beds, often during reverse or thrust faulting episodes.

overvoltage

Higher than normal voltage.

overvoltage reflections

High voltage spikes commonly created as a result of long cabling or short PWM rise times.

overvoltage relay

A relay tripping when voltage rises above a set value.

OWC

Oil-water contact: the surface in a reservoir above which oil predominates and below which water does, marking the deepest producible oil.

OWR

Oil/water ratio — the proportion of oil to water in the liquid phase of an oil mud.

oxidation

The combination of a substance with oxygen to form a new substance; a reaction in which a substance loses electrons.

oxidation inhibitor

An additive that helps prevent gum from forming in diesel fuel if the fuel is exposed to oxygen while it is in storage.

oxidation reduction potential

The electrochemical potential that exists in a chemical reaction involving an exchange of ions. Abbreviated as ORP. Also called a redox reaction.

oxide-closure model

A method converting relative elemental yields from spectroscopy logging into absolute weight fractions by requiring the oxides to sum to one.

oxides

An oxide is a binary compound of oxygen with another element.

oxidizer

A chemical (other than a blasting agent or explosive) that initiates or promotes combustion in other materials, causing fire either of itself or through the release of oxygen or other gases. It presents a fire and explosion hazard on contact with organic compounds and other oxidizable substances.

O