Oil and Gas Terms Beginning with “C” — Page 12

A small-diameter hydraulic line used to operate downhole completion equipment such as the surface controlled subsurface safety valve (SCSSV). Most systems operated by control line operate on a fail-safe basis. In this… Read more →

(noun) A directional survey method in which measurements of wellbore inclination and azimuth are taken at predetermined time intervals or depth stations during drilling operations to monitor the trajectory of the… Read more →

The density- and heat-driven cycling, transfer or circulation of energy through which material initially warms up and becomes relatively less dense, then rises, cools and becomes relatively more dense, and finally… Read more →

A term that, in the past, referred to a mud containing bentonite clay, water, caustic soda and perhaps barite (as needed for density) usually with lignite or lignosulfonate present. Modern drilling does not necessarily… Read more →

A reservoir in which buoyant forces keep hydrocarbons in place below a sealing caprock. Reservoir and fluid characteristics of conventional reservoirs typically permit oil or natural gas to flow readily into wellbores.… Read more →

The effect of performing computations using a planar surface instead of the curved surface of survey measurements. A convergence correction accommodates the change from rectangular coordinates to latitude and longitude. Read more →

A seismic wave that changes from a P-wave to an S-wave, or vice versa, when it encounters an interface. Read more →

A written contract between a grantor and grantee, used to transfer title or rights to real estate or property. Typical conveyances include oil, gas and mineral leases; assignments; deeds and rights of way. Read more →

A mathematical operation that uses downhole flow-rate measurements to transform bottomhole pressure measurements distorted by variable rates to an interpretable transient. Convolution also can use surface rates to… Read more →

A polymer that is formed from two or more different structural units. Read more →

A compound, CuCO3, that was used as a sulfide scavenger for water-base muds. However, it was found to be corrosive due to spontaneous plating of metallic copper onto metal surfaces, causing pitting corrosion; it has… Read more →

A cylindrical sample of geologicformation, usually reservoirrock, taken during or after drilling a well. Cores can be full-diameter cores (that is, they are nearly as large in diameter as the drill bit) taken at the… Read more →

Laboratory study of a sample of a geologicformation, usually reservoirrock, taken during or after drilling a well. Economic and efficient oil and gas production is highly dependent on understanding key properties of… Read more →

A log obtained in the laboratory by moving the core past a gamma ray detector. The log can be of the total gamma ray in API units, or of the spectral response in weight concentrations of thorium, uranium and potassium.… Read more →

An image of the external or internal features of a core. External images are photographs taken under natural or ultraviolet light; natural light highlights lithology and sedimentary structures, while ultraviolet light… Read more →

A plug, or sample, taken from a conventional core for analysis. Core plugs are typically 1 in. to 1 1/2 in. [2.5 to 3.8 cm] in diameter and 1 in. to 2 in. [5 cm] long. Core plugs are ordinarily cut perpendicular to the… Read more →

Laboratory analyses performed on formationcore samples as part of a stimulation-treatment design process. Tests such as the formation flow potential, fracture orientation and fluid compatibility tests are commonly run… Read more →

What Is Coreflooding? Coreflooding is a laboratory test in which fluids are injected through a core plug or core composite at controlled temperature, pressure, and flow rate to measure reservoir rock properties under… Read more →

A specially designed fluid that is used for cutting cores with a core barrel and core bit. Sometimes the fluid used is the drilling mud, but if cores are for special studies, the coring fluid must be carefully designed… Read more →

The result of certain drilling conditions that cause the borehole to take the shape of a corkscrew. Most logging tools are much longer than the wavelength of the corkscrew, and therefore see it as a change in standoff… Read more →

A gamma ray log from which the uranium contribution has been subtracted. In some rocks, and in particular in carbonate rocks, the contribution from uranium can be large and erratic, and can cause the carbonate to be… Read more →

A procedure for correcting pressure measurements in a reservoir to a common datum level. This is not required for calculating kh, permeability thickness, and s, skin effect, but is required for determining average… Read more →

A positive relationship between data samples that implies a connection or a relationship between them. Read more →

A log run for the purpose of correlating between wells. The most common logs used for this purpose are the gamma ray, the resistivity and the acoustic log; the most common depth scales are 1/500 and 1/1000, or 2 in./100… Read more →

A graphical representation of the degree of agreement between segments of curves being correlated between different wells. The degree of lag (required shift), the amplitude of the peaks and the shapes of the peaks are… Read more →

The loss of metal due to chemical or electrochemical reactions, which could eventually destroy a structure.Corrosion can occur anywhere in the production system, either at bottomhole or in surface lines and equipment.… Read more →

The measures used to prevent or considerably reduce the effects of corrosion. Corrosion can occur anywhere in the production system, either at bottomhole or in surface lines and equipment. Some practices for corrosion… Read more →

A specimen of test material to be used in a corrosion test, usually a metal strip or ring shaped to fit into a testing cell or between joints of drillpipe. Rings, or coupons, are weighed before and after exposure, and… Read more →

A type of corrosion in which the metal components of a structure fail due to cyclic stresses applied in a corrosive environment, such as salt water. Consequently, a break in the metal will occur at stresses considerably… Read more →

What Is a Corrosion Inhibitor in Oil and Gas? A corrosion inhibitor is a chemical compound injected into oil and gas production systems to reduce the rate of metal deterioration caused by corrosive fluids — primarily… Read more →