Oil and gas terminology · MLC-0103

Oil and gas terms: O (94)

• OBCOcean-bottom cable, a type of marine seismic acquisition system where receivers are deployed on the seafloor...
• OBROil-based drilling fluid, a type of drilling mud where oil forms the continuous phase and water is dispersed...
• ObserverThe person responsible for managing the quality control and technical operations of a seismic acquisition...
• Occam's inversionA geophysical inversion technique that seeks the simplest model (in terms of roughness or complexity) that...
• Ocean-bottom cableA type of marine seismic acquisition system where receivers are deployed on the seafloor rather than towed in...
• OCMAAn acronym for the Oil Companies Materials Association, a former organization that published standards and...
• Octahedral layerA structural component of clay minerals, consisting of aluminum or magnesium ions surrounded by six hydroxyl...
• OctanolAn eight-carbon alcohol, specifically 1-octanol, used as a defoamer or foam suppressant in drilling fluids...
• Octyl alcoholA type of higher-molecular-weight alcohol, also known as 1-octanol, used as a defoamer in drilling fluids. It...
• ODThe external dimension across a cylindrical component, such as drill pipe, casing, or a downhole tool. This...
• Off-pattern wellA well drilled outside the regular geometric arrangement of injection and production wells in a developed...
• OffsetThe horizontal displacement of rock layers or a geological feature, such as a reservoir boundary, across a...
• Offset vertical seismic profileA type of vertical seismic profile (VSP) where the seismic source is positioned at a horizontal distance from...
• Offset VSPA type of Vertical Seismic Profile (VSP) where the seismic source is positioned at a lateral distance from...
• Offset wellA well drilled in proximity to an existing well to gather geological data, evaluate a different part of the...
• Ohm's lawA fundamental principle of electricity stating that the current flowing through a conductor is directly...
• Oil and gas leaseA legal agreement between a mineral owner (lessor) and an oil company (lessee) that grants the company the...
• Oil and gas separatorA pressure vessel designed to separate a well stream into its constituent components: oil, gas, and water...
• Oil bankA zone of accumulated oil that forms ahead of the displacing fluid front during an enhanced oil recovery...
• Oil contentThe volume percentage of oil in a sample of drilling fluid, cuttings, or produced water. In drilling fluids...
• Oil fieldA geographical area containing one or more oil reservoirs, typically sharing a common geological structure or...
• Oil formation volume factorThe ratio of the volume of oil at reservoir conditions (pressure and temperature) to its volume at standard...
• Oil kitchenA subsurface region where organic-rich source rocks have reached sufficient temperature and pressure...
• Oil miningA method of extracting oil from shallow, heavy oil deposits or oil sands by surface mining techniques, rather...
• Oil mudA drilling fluid in which oil is the continuous phase and water is the dispersed phase, forming an invert...
• Oil on cuttingsThe quantity of oil-based or synthetic-based drilling fluid adhering to drill cuttings when they reach the...
• Oil poolA subsurface accumulation of crude oil within a porous and permeable rock formation, sealed by an impermeable...
• Oil sandA naturally occurring mixture of sand, clay, water, and bitumen, a heavy, viscous form of petroleum. The...
• Oil swellingThe increase in volume of crude oil when it absorbs an injected gas, such as carbon dioxide or a hydrocarbon...
• Oil wellA borehole drilled into the earth to extract crude oil from a subsurface reservoir. These wells are completed...
• Oil-base mudA drilling fluid system where oil forms the continuous phase, and water is emulsified within it as the...
• Oil/brine ratioThe volumetric proportion of oil to brine in an oil-based drilling fluid or emulsion. This ratio is a key...
• Oil-emulsion mudA drilling fluid where oil is dispersed as droplets within a continuous water phase, stabilized by...
• OilfieldA geographical area containing one or more oil reservoirs, typically sharing a common geological structure or...
• Oilfield batteryA collection of production equipment, including separators, tanks, and pumps, located at a central site to...
• Oil-in-water emulsionA fluid system where small droplets of a non-aqueous liquid, such as oil or synthetic fluid, are dispersed as...
• Oil-mud emulsifierA chemical additive used to stabilize the emulsion in oil-based drilling fluids, preventing the separation of...
• Oil-water contactThe boundary surface within a reservoir rock where crude oil and formation water meet. Due to density...
• Oil-water interfaceThe boundary surface between an oil phase and a water phase within a drilling fluid or reservoir. This...
• Oil/water ratioThe volume percentage of the oil (or synthetic fluid) and water phases in an invert-emulsion drilling fluid...
• Oil-wetDescribing a rock surface or pore throat that preferentially attracts and is coated by oil rather than water...
• Olefinic hydrocarbonAn organic compound containing at least one carbon-carbon double bond, belonging to the alkene family...
• OligomerA polymer composed of a relatively small number of repeating monomer units, typically fewer than ten. In...
• One-dimensional (1D) seismic dataSeismic data that represents subsurface properties varying only with depth, assuming horizontal layering and...
• One-way timeThe time taken for a seismic wave to travel from the source to a reflector in the subsurface. This is half of...
• OnlapA stratigraphic relationship where younger sedimentary layers terminate progressively against an older...
• OOCAn abbreviation for "oil on cuttings," which describes the presence of oil adhering to drill cuttings...
• Open flow potentialThe maximum theoretical rate at which a gas well could produce if there were no restrictions to flow, such as...
• Open holeThe section of a wellbore that has been drilled but has not yet been cased or lined with pipe. This exposed...
• Open sourceRelating to software for which the original source code is made freely available and may be redistributed and...
• OpenholeDescribing the section of a wellbore that remains uncased after drilling, exposing the formation directly to...
• Openhole completionA well completion method where the production casing is set above the reservoir interval, leaving the...
• Openhole gravel packA sand control technique applied in an openhole completion where a permeable screen is run into the uncased...
• Openhole packerA downhole tool used to isolate sections of an uncased wellbore during testing, stimulation, or completion...
• Openhole testA temporary well test conducted in an uncased wellbore to evaluate reservoir characteristics before...
• Opening bombA specialized downhole tool, typically run on wireline, used to open a sliding sleeve or other flow control...
• Operating agreementA contract among co-owners of an oil and gas leasehold that governs the exploration, development, and...
• Operating gas-lift valve (OGLV)The primary, lowermost valve in a gas-lift system through which injection gas continuously enters the...
• Operating interestA working interest in an oil and gas lease that carries the obligation to pay a share of the costs of...
• OperatorThe company or entity responsible for the day-to-day management and execution of drilling, completion, and...
• Optical indexA measurement of a fluid's refractive index, used by downhole optical probes to differentiate between...
• Optical probeA downhole sensor that uses light to detect and characterize fluid phases in a wellbore. It typically...
• OrchestrationThe automated configuration, coordination, and management of complex computer systems, services, and software...
• Organic acidA type of acid containing carbon atoms, such as formic acid or acetic acid, used in well stimulation and...
• Organic depositAccumulations of hydrocarbon-based solids, such as paraffin waxes or asphaltenes, that precipitate from crude...
• OrganophilicDescribing a substance that has an affinity for oil or organic compounds, meaning it readily mixes with or...
• Organophilic clayA clay mineral, such as bentonite, that has been chemically treated with organic cations to make its surface...
• Orifice meterA differential pressure flow meter that measures fluid flow rate by creating a pressure drop across a...
• Orifice valveA type of gas-lift valve that contains a fixed-size opening, or orifice, for the continuous injection of gas...
• O-ringA circular, elastomeric seal with a round cross-section, commonly used to prevent fluid or gas leakage...
• OrogenicRelating to or resulting from orogeny, the process of mountain building, which involves intense deformation...
• OrogenyA geological process of mountain building that involves the deformation of the Earth's crust, forming folds...
• OSHAThe United States government body, the Occupational Safety and Health Administration, tasked with setting and...
• OsmosisThe passive movement of solvent molecules, typically water, across a semipermeable membrane from an area of...
• Osmotic pressureThe pressure difference that develops across a semipermeable membrane separating two solutions of different...
• OutcropAn exposure of bedrock or an older geological formation at the Earth's surface, unobscured by soil or recent...
• Outside diameterThe external dimension of a cylindrical object, such as a pipe, casing, or tubing, measured across its...
• Ovality limitThe maximum permissible deviation from a perfectly circular cross-section for a tubular component, such as...
• Over travelThe additional distance a downhole tool or component moves beyond its intended or designed stopping point...
• OverbalanceA condition where the hydrostatic pressure exerted by the drilling fluid column in the wellbore is...
• OverburdenThe rock and sediment layers that lie above a target formation in the subsurface. This material exerts...
• OverflushA volume of fluid injected into a well after a primary treatment fluid, such as acid or a proppant slurry...
• OvermatureDescribing a source rock that has been subjected to temperatures and pressures beyond the optimal window for...
• OverpressurePore fluid pressure that exceeds the normal hydrostatic pressure expected at a given depth, which is the...
• Overriding royaltyA fractional share of the gross production of oil and gas, free of the costs of exploration, development, and...
• Overriding royalty interestA percentage of the gross production of oil and gas, free of all costs of drilling and producing, that is...
• OvershotA fishing tool used in well intervention to retrieve lost or stuck equipment from the wellbore. It consists...
• OverthrustA type of thrust fault with a very low dip angle, where older rock units are pushed over younger ones for a...
• OvertravelThe additional distance a downhole tool or component moves beyond its intended set point or operational...
• OWCThe depth or surface within a reservoir that separates the zone containing mobile oil from the underlying...
• OWRAn abbreviation for "oil/water ratio," which represents the volumetric proportion of oil to water in a...
• Oxide-closure modelA geochemical model used to interpret elemental concentration logs by converting the measured weight...
• Oxygen activationA nuclear logging technique that uses pulsed neutrons to activate oxygen atoms in the formation and fluids...
• Oxygen scavengerA chemical additive introduced into drilling fluids to remove dissolved oxygen, which can cause corrosion of...

94 of 4,499 terms in Oil and gas terminology (MLC-0103). Request the full dataset.