Oil and Gas Terms Beginning with “C” — Page 14

Crossover (also called a crossover sub) in drilling engineering is a short tubular subassembly machined with two different API or premium thread connections, one on each end, used to join two drill string or bottom hole… Read more →

A crossover service tool (also called a crossover tool, crossover sub, or crossover adapter) is a downhole completion or intervention device that enables the fluid communication pathway in the wellbore to be redirected… Read more →

A crossplot in petroleum geoscience and engineering is a scatter diagram in which two different measurements or calculated parameters from the same set of samples (core plugs, well log depths, or seismic traces) are… Read more →

Crossplot porosity is an estimate of formation porosity derived by combining the readings from two different porosity-sensitive well logs (most commonly the neutron porosity log and the density log) to cancel or reduce… Read more →

What Is Crosswell Electromagnetic Tomography? Crosswell electromagnetic (EM) tomography is a borehole geophysical technique that measures the electromagnetic field transmitted between two wellbores at low frequencies (1… Read more →

Crosswell reflection tomography is a borehole seismic imaging technique in which a seismic source deployed in one well and a hydrophone or geophone receiver array deployed in an adjacent well are used to record both… Read more →

What Is Crosswell Seismic Tomography? Crosswell seismic tomography is a borehole geophysics technique that generates seismic waves in one wellbore and records them in a second parallel wellbore, using the travel times… Read more →

Crosswell tomography is a specialized geophysical technique for measuring formation properties between two adjacent wells by deploying a transmitter or source in one well and a receiver array in a neighboring well, with… Read more →

What Is a Crown Block? Crown block (also called the crown sheave assembly or crown pulley block ) is the stationary assembly of sheaves (pulleys), their supporting steel frame, and associated bearings mounted at the… Read more →

(noun) A valve installed at the top of a Christmas tree or wellhead assembly that provides the uppermost point of closure on the vertical bore of the tree, used to isolate the well during wireline operations,… Read more →

What Is Crude Oil? Crude oil is a naturally occurring liquid petroleum extracted from subsurface geological formations, composed primarily of hydrocarbon chains and varying concentrations of sulfur, nitrogen, oxygen,… Read more →

The crushed zone in perforating is the highly compacted, severely damaged annular region of rock and debris immediately surrounding a perforation tunnel created by the high-velocity jet from a shaped explosive charge,… Read more →

The crust is the outermost solid shell of the Earth, divided into thin, dense oceanic crust (5 to 10 km thick, composed of mafic basaltic rock with density 2.9 to 3.0 g/cm3) and thicker, less dense continental crust (25… Read more →

Crystallization temperature in petroleum engineering is the temperature at which dissolved salts begin to precipitate out of a clear brine solution as solid crystals, defining the lower operational limit of the brine… Read more →

Cubic packing is the specific arrangement in space of uniform spheres (representing atoms and molecules in mineral crystals or grains in clastic sedimentary rocks) that produces a cubic material structure with… Read more →

Cultural anomaly in applied geophysics is a local deviation in a measured geophysical field (magnetic intensity, gravitational acceleration, electrical resistivity, electromagnetic response, or seismic velocity) that is… Read more →

Cultural noise in applied geophysics is time-varying, unwanted energy generated by human activity that contaminates geophysical measurements and must be distinguished from, and suppressed relative to, the geological… Read more →

What Is Cumulative Production? Cumulative production (also called Np for oil, Gp for gas, or simply cum production ) is the total volume of hydrocarbons or water produced from a well, reservoir, or field from the date… Read more →

The aging of cement under specific temperature and pressure conditions. Read more →

The presentation on hard copy of log data from a single measurement versus depth. The term is also used to refer to the log data themselves, as a synonym for a single log. Read more →

The generation of a theoretical equation to define a given data set. In contrast, curve matching involves the comparison of well-understood data to a data set of interest. Read more →

Curve matching in petroleum engineering is an analytical technique used in both pressure transient analysis and production decline analysis to determine reservoir and well properties by finding the theoretical model… Read more →

A cushion in drilling and well testing operations refers to a volume of fluid — typically a lighter density fluid (diesel oil, fresh water, nitrogen gas, or weighted brine) — placed below the test string in a drill stem… Read more →

In production engineering the word cut denotes the fraction of a well's total produced flow that is contributed by one particular fluid phase, normally quoted at standard surface conditions of temperature and pressure.… Read more →

Cut oil is crude oil contaminated with water in emulsified form, typically as a stable water-in-oil emulsion where micron-scale water droplets are dispersed throughout the continuous oil phase and stabilized by natural… Read more →

A cut point in petroleum refining and crude oil processing is the distillation temperature boundary that defines the separation between two adjacent petroleum fractions — the temperature at which the boiling point… Read more →

The cut-and-thread fishing technique is a wellbore fishing procedure used to recover a stuck tubular or workstring from a wellbore by first cutting the stuck pipe at a selected depth above the obstruction point, then… Read more →

Cuttings (also called drill cuttings or drilling cuttings) are the rock fragments dislodged from the formation by the drill bit as it penetrates subsurface rocks during the drilling of an oil or gas well, transported… Read more →

A condensate (liquid hydrocarbon) produced at surface from cycle gas. Read more →

Cycle gas in petroleum drilling is the gas that appears in the drilling fluid returns at the surface after completing a full circulation of the wellbore volume — the time required for drilling fluid pumped down the… Read more →