Oil and Gas Terms Beginning with “C” — Page 6

In seismic data acquisition, a channel is a single independent data path from a receiver group (an array of geophones or hydrophones) through the field electronics to the recording system. Each channel amplifies,… Read more →

A channel wave (also called an in-seam wave, seam wave, or guided seismic wave) is a seismic wave that propagates preferentially within a thin, low-velocity geological layer by total internal reflection at the layer… Read more →

Channeling in a reservoir waterflood or gas injection program refers to the preferential flow of injected fluid through high-permeability streaks, fractures, or thief zones rather than distributing uniformly through the… Read more →

Seismic character refers to the ensemble of measurable and visually distinctive attributes of a seismic reflection event that together define its signature on a seismic section or volume, encompassing amplitude (the… Read more →

A charged zone in petroleum well logging and formation evaluation refers to a permeable reservoir interval that has been invaded by drilling fluid filtrate under differential pressure during the drilling process,… Read more →

A check valve is a one-way flow control device that permits fluid to pass in the intended direction while automatically blocking reverse flow when the differential pressure across the valve reverses, operating without… Read more →

A check shot survey is a borehole seismic measurement in which a seismic source at surface fires and a downhole geophone clamped to the borehole wall records the first-arrival travel time of the compressional (P-wave)… Read more →

A chelate is a cyclic coordination complex formed when a polydentate ligand (a molecule or ion with two or more electron-donor atoms) binds simultaneously to a central metal ion through multiple coordinate bonds,… Read more →

A chelating agent in oilfield chemistry is a polydentate organic molecule that forms stable, water-soluble chelate complexes with metal ions by binding through two or more electron-donor atoms simultaneously, thereby… Read more →

Chelation in oilfield chemistry is the process by which a polydentate organic ligand (the chelating agent) forms a stable, water-soluble ring complex with a metal ion by simultaneously donating electrons from two or… Read more →

A chemical barrel in drilling fluid engineering is the standard volumetric unit of 42 United States gallons (approximately 158.99 litres) used to express drilling fluid system volume, chemical addition rates, and… Read more →

A chemical cutter is a downhole pipe-severing tool that uses the high-velocity jet of a chemically reactive fluid (typically a concentrated oxidizing acid or an oxidizer-fuel mixture) discharged radially through… Read more →

Chemical diversion in matrix acid stimulation is the practice of using a chemical agent injected into the wellbore ahead of, mixed with, or following the acid treatment stage to temporarily reduce the injectivity of… Read more →

A chemical diverter is a specific fluid, particle, or chemical system injected into a wellbore during a matrix acid stimulation or waterflood treatment to temporarily reduce the injectivity of the dominant… Read more →

Chemical flooding is an enhanced oil recovery (EOR) method in which chemicals dissolved or dispersed in an aqueous injection fluid are used to improve the displacement efficiency of a waterflood beyond what water alone… Read more →

Chemical injection in oil and gas production is the continuous or batch delivery of production chemicals through dedicated injection systems to specific points in the wellbore or surface facility where the chemicals are… Read more →

A chemical neutron source in oilfield well logging is a radioactive device that produces neutrons through a nuclear reaction between an alpha-emitting radioisotope and a beryllium target, where the alpha particles… Read more →

Chemical oxygen demand (COD) is a laboratory measurement that quantifies how much oxygen would be needed to chemically oxidize all the organic and inorganic oxidizable material in a water sample. It is expressed in… Read more →

Chemical potential in thermodynamics is the partial molar Gibbs free energy of a component in a mixture, defined as the rate of change of the total Gibbs free energy of the system with respect to the number of moles of… Read more →

A chemical wash in oilfield cementing operations is a low-viscosity, chemically active fluid pumped ahead of the cement slurry in the cementing train to clean drilling mud and mud cake from the casing interior and the… Read more →

Chemical marker injection in reservoir surveillance is the introduction of a detectable tracer compound into an injection well fluid stream (water, gas, or steam) so that its subsequent detection at one or more… Read more →

Chert is a fine-grained, extremely hard sedimentary rock composed almost entirely of microcrystalline or cryptocrystalline silica (SiO2) with individual quartz crystals ranging from less than 1 micrometre to 30… Read more →

The chloride test in oilfield drilling and production operations is an analytical procedure that measures the concentration of chloride ions (Cl-) in drilling mud filtrate, produced water, or formation water samples,… Read more →

Chlorite in petroleum geology and reservoir engineering is an iron-magnesium-aluminum phyllosilicate clay mineral (general formula (Fe,Mg,Al)6(Si,Al)4O10(OH)8) that occurs as a diagenetic cement, pore-lining coating,… Read more →

A choke in petroleum production and well testing is a flow restriction device installed in the production flowline or wellhead assembly that controls the rate of fluid flow from the well by creating a pressure drop… Read more →

The choke line in oilfield well control is a high-pressure conduit that connects the blowout preventer (BOP) stack to the choke manifold at the surface, providing a controlled flow path through which wellbore fluids… Read more →

The choke manifold in oilfield well control is the surface pressure control assembly connected to the choke line from the BOP stack that contains a series of manually operated and hydraulically actuated valves, fixed… Read more →

Chromate salts in oilfield operations are water-soluble inorganic compounds of hexavalent chromium (Cr6+), principally sodium chromate (Na2CrO4), potassium chromate (K2CrO4), and sodium dichromate (Na2Cr2O7), that were… Read more →

Chrome-free drilling fluid additives are water-base mud (WBM) chemical products that perform the thinning, dispersing, and filtration-control functions traditionally accomplished by chrome lignosulfonate (CLS) without… Read more →

Chrome lignite in oilfield drilling fluid engineering is a high-temperature filtration control additive produced by treating oxidized lignite (leonardite) with chromium salts to form chromium-humate complexes that… Read more →