Oil and Gas Terms Beginning with “C” — Page 8

Clear water drilling solids control refers to the integrated mechanical and chemical treatment processes applied to the circulating water stream in a clear water drilling program to remove formation cuttings, dispersed… Read more →

Close-in pressure in oil and gas well operations refers to the stabilized wellhead or bottomhole pressure measured after a producing well has been shut in for a defined period sufficient to allow near-wellbore pressure… Read more →

A closed mud system is a drilling fluid management configuration in which all drilling returns, waste mud, and drilled cuttings are processed and contained within a sealed, integrated solids control circuit without… Read more →

Closed-chamber testing (CCT) is a drillstem test variant in which the drill string remains in the hole with the surface valve closed, creating a sealed chamber of precisely known internal volume into which reservoir… Read more →

A closed-in well is a producing, injection, or appraisal well in which all surface flow valves have been shut and the wellbore is sealed at the wellhead, preventing fluid or gas from flowing to the surface processing… Read more →

A closing unit is the hydraulic power system mounted on or adjacent to a drilling rig that stores pressurized hydraulic fluid in nitrogen-precharged accumulator bottles and delivers the high-pressure hydraulic flow… Read more →

Closure in petroleum geology and reservoir engineering is the three-dimensional geometry of a structural or stratigraphic trap that confines hydrocarbons within a definable volume bounded laterally and vertically by the… Read more →

Closure pressure in hydraulic fracture engineering is the fluid pressure at which a hydraulic fracture mechanically closes after injection stops, numerically equal to the minimum principal in-situ stress acting… Read more →

Cloud point is the temperature at which dissolved wax crystals (long-chain n-paraffin molecules, predominantly C20 to C40+) first nucleate and become visible as a hazy turbidity in a petroleum fluid, crude oil,… Read more →

A perforation cluster in hydraulic fracturing completions is a group of perforations shot within a short interval (typically 0.3 to 1.5 m) of casing at a single depth station, with each cluster containing 4 to 8… Read more →

Cluster analysis in petroleum geoscience and petrophysics is a multivariate statistical technique that partitions a dataset of observations (wireline log readings, core measurements, or production parameters) into… Read more →

Coal in the context of the oil and gas industry is a sedimentary organic rock formed from the compaction and diagenesis of plant material accumulated in ancient swamp and peat bog environments, relevant to petroleum… Read more →

Coalescence in oil and gas production engineering is the physical process by which small dispersed droplets of one liquid phase collide, drain the thin continuous-phase film trapped between their interfaces, and merge… Read more →

Coarse solids in drilling fluid technology refers to solid particles larger than 74 micrometres (retained on a No. 200 US standard mesh sieve), which in a water-base or oil-base mud system include the drilled formation… Read more →

Coating in the oil and gas pipeline and facility context is a layer of protective material applied to the external or internal surface of steel pipe, vessels, tanks, and structural components to prevent corrosion from… Read more →

Coating flaw (also called a holiday or coating defect) in pipeline integrity engineering is a discontinuity in the external or internal protective coating of a buried or submerged steel pipeline or vessel that exposes… Read more →

Well coding in Western Canada petroleum regulation refers to the standardized classification system used by provincial energy regulators to categorize each wellbore by its intended purpose, production type, and… Read more →

Cogeneration (also called combined heat and power, CHP) in oil and gas facility engineering is the simultaneous production of electrical power and useful thermal energy from a single fuel source, recovering heat that a… Read more →

Coherence in 3D seismic interpretation is a volumetric attribute that quantifies the lateral similarity of waveforms between adjacent seismic traces over a short vertical analysis window, producing a normalized measure… Read more →

Coherence filtering (also called structure-oriented filtering or dip-steered filtering) in seismic data processing is a noise-attenuation technique that applies a smoothing filter oriented along the local dip and… Read more →

A coherence map in 3D seismic interpretation is a two-dimensional image extracted from a three-dimensional coherence volume that displays lateral waveform similarity between adjacent seismic traces on a time slice,… Read more →

A coherence vector map in 3D seismic interpretation is a directional attribute display derived from a coherence volume that shows not only the magnitude of lateral waveform dissimilarity at each sample location in the… Read more →

In seismic interpretation, "coherent" describes seismic events (reflections) that show continuity from one trace to the next across a seismic section. A coherent reflector traces smoothly across many adjacent traces,… Read more →

Coherent noise in seismic data acquisition and processing is any unwanted energy that exhibits a predictable, repeatable pattern across adjacent seismic traces, propagating with a consistent apparent velocity, frequency… Read more →

Coil shooting acquisition (also called circular shooting or continuous-azimuth marine seismic) is a marine seismic acquisition method in which the vessel sails overlapping circular paths of 3 to 8 km radius rather than… Read more →

Coiled tubing (CT) is a continuous string of small-diameter high-strength steel tube, manufactured in lengths of 4,000 to 9,000 m and wound on a large surface reel, that is run into oil and gas wellbores without… Read more →

Coiled tubing completion is a well completion technique in which a continuous coiled tubing string serves as the primary mechanical delivery system for perforation guns, frac plug assemblies, velocity string… Read more →

A coiled tubing connector (also called a CT end fitting, CT bottom connector, or BHA connector sub) is the pressure-rated mechanical fitting at the lower end of a coiled tubing string that bridges the interface between… Read more →

Coiled tubing drilling (CTD) is a drilling technique that uses a continuous steel coiled tubing string (typically 60 mm to 89 mm OD) to convey a positive displacement motor (PDM), measurement-while-drilling (MWD)… Read more →

A coiled tubing string (also called a CT string or CT pipe) is the continuous, unjointed steel tube wound on a surface reel and deployed into oil and gas wellbores to convey downhole tools and fluids for well… Read more →