Oil and Gas Terms Beginning with “O” — Page 2

In the context of heavy oil, an oil sand is a porousrocklayer, often considered to be a mixture of sand, clay, water, and bitumen. The term is predominantly used in Canada, where over 170 billion barrels of bitumen are… Read more →

An expansion in oil volume that can occur when a solvent contacts a reservoir fluid. The swelling is due to the complete or partial dissolution of the solvent molecules into the reservoir fluid. The amount of swelling… Read more →

A producing well with oil as its primary commercial product. Oil wells almost always produce some gas and frequently produce water. Most oil wells eventually produce mostly gas or water. Read more →

An invert-emulsionmud, or an emulsion whose continuous phase is oil. In the past, the term referred to an oil mud containing less than about 5 vol.% water. This definition, at the time, distinguished mud with less than… Read more →

A dispersion of oil droplets into an aqueous medium. This describes an emulsion mud, as contrasted with an invert-emulsion mud. The term should not be used to refer to synthetic-in-water emulsion because a synthetic… Read more →

A chemical used in preparation and maintenance of an oil- or synthetic-base drilling fluid that forms a water-in-oil emulsion (invert emulsion). An oil-mud emulsifier lowers the interfacial tension between oil and… Read more →

The quality of a source rock that makes it more likely to generate oil than gas. The nature of the organic matter (kerogen) in source rocks varies from coaly, plant-like material commonly found in terrestrial source… Read more →

A bounding surface in a reservoir above which predominantly oil occurs and below which predominantly water occurs. Although oil and water are immiscible, the contact between oil and water is commonly a transition zone… Read more →

The surface of contact between a water layer and an oil layer. Read more →

Pertaining to the preference of a solid to be in contact with an oil phase rather than a water or gas phase. Oil-wet rocks preferentially imbibe oil. Generally, polar compounds or asphaltenes deposited from the crude… Read more →

Ratio of the volume percent oil to the volume percent brine in an oil mud, in which each is expressed as a percent of the total liquid in the mud. OBR is determined by retort analyses of oil and water content, but the… Read more →

Ratio of the volume percent oil to the volume percent water in an oil mud, where each is a percent of the total liquid in the mud. OWR is calculated directly from the retort analysis of an oil mud. For example, if a mud… Read more →

An electrochemical source that provides electrical power to a downhole or surface tool used for determining the location or assisting in the extraction of hydrocarbons. Unlike a conventional battery, an oilfield battery… Read more →

The group of hydrocarbon compounds that has one or more double or triple bonds between carbon atoms in the linear chain. Ethylene, C2H2, is the smallest olefin. Synthetic olefinic hydrocarbons are made by polymerization… Read more →

A low-molecular-weight polymer typically with two to five monomer units. Read more →

(noun) A single seismic trace recording the amplitude of reflected seismic energy as a function of two-way travel time at one surface location, providing a vertical profile of acoustic impedance contrasts in the… Read more →

The time measured from a check-shot survey or vertical seismic profile (VSP), which is the time energy takes to travel from an energy source at the surface of the Earth to a receiver at a depth of interest. Read more →

The termination of shallowly dipping, younger strata against more steeply dipping, older strata, or the termination of low-angle reflections in seismic data against steeper reflections. Onlap is a particular pattern of… Read more →

The uncased portion of a well. All wells, at least when first drilled, have openhole sections that the well planner must contend with. Prior to running casing, the well planner must consider how the drilled rock will… Read more →

What Is Open-Flow Potential? The open-flow potential (OFP) is the maximum theoretical flow rate a well could sustain if the wellbore flowing pressure were reduced to zero (atmospheric) — representing the absolute upper… Read more →

A well completion that has no casing or liner set across the reservoirformation, allowing the produced fluids to flow directly into the wellbore. This type of completion suffers the major disadvantage that the sandface… Read more →

A type of sand-control completion in which the gravel pack screen is packed off in an openhole section with no casing or liner to support the producing formation. The openhole interval is often prepared by underreaming… Read more →

A type of packer designed for use in openhole applications such as drillstem testing. Openhole packers are typically configured with one large element that can be deformed easily to contact the uneven formation surface,… Read more →

A drillstem test performed in an openhole section of the wellbore. The test once was a popular method of assessing the productivity of exploration wells without the need to runcasing or liner across the reservoir… Read more →

A device used in stage cementing to open the stage collar or diverting valve through which the second or subsequent cement stage is placed. The opening bomb is dropped down the casing string to land in a seat within the… Read more →

An agreement between parties who own a working interest in a well that sets out responsibilities and duties of the operator and nonoperators, including drilling the test well and subsequent wells, and sharing of… Read more →

The lowermost gas-lift valve in a gas-lift completion through which the lift gas is injected during normal production. During startup, the upper gas-lift valves open in sequence, from the top down, to enable the tubing… Read more →

Ownership by a lessee, company or working interest owner, which is burdened with the costs of leasing the acreage and drilling and operating a well. Read more →

The owner of the right to drill or produce a well, or the entity contractually charged with drilling of a test well and production of subsequent wells. Read more →

A measure of the amount of light reflected by a fluid from an optical probe. It is the same as the relative refractive index of light between the probe and the fluid, being close to 1 in gas, 1.35 in water and 1.5 in… Read more →