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

Drilling operations using a water-base drilling fluid that contains few solids. Clear-water drilling is done in "hard rocks" in which density and fluid loss are not critical. Rapid drilling rate is the incentive for… Read more →

To close a valve to stop or isolate fluid flow. The term is most commonly applied to "closing-in the well," meaning isolation of the wellbore by closing the master valve. Read more →

What Is a Closed Mud System? Closed mud system (also called a zero-discharge system or closed-loop drilling system) is a surface drilling fluid management configuration that collects, treats, and recirculates all… Read more →

What Is Closed Chamber Testing? Closed chamber testing (CCT; also called closed chamber drill stem testing or pressure build-up chamber testing) is a formation evaluation technique used in exploratory and appraisal… Read more →

What Is a Closed-In Well? A closed-in well is a well in which all surface valves have been shut and the wellbore is sealed — no fluid or gas is flowing to surface — allowing wellbore pressure to build up toward the… Read more →

What Is a Closing Unit? Closing unit (also called a BOP accumulator unit or accumulator skid) is the hydraulic power system that stores pressurized hydraulic fluid in nitrogen-charged accumulator bottles and delivers… Read more →

The area, or areal closure, included in the lowest closing contour of a trap. Measurements of both the areal closure and the distance from the apex to the lowest closing contour are typically incorporated in… Read more →

What Is Closure Pressure? Closure pressure (also called fracture closure pressure or minimum in-situ stress) is the fluid pressure at which a hydraulic fracture closes after injection stops — it equals the minimum… Read more →

What Is a Cloud Point? Cloud point (also called wax appearance temperature or WAT) is the temperature at which dissolved wax, paraffin, or asphaltene crystals begin to nucleate and become visible as a cloudy haze in a… Read more →

The act of determining clusters from data sets. Read more →

Mathematical techniques for summarizing large amounts of multidimensional data into groups. The two most popular techniques are: hierarchicalk-means.The hierarchical system calculates as many clusters as there are data… Read more →

A carbon-rich sedimentaryrock that forms from the remains of plants deposited as peat in swampy environments. Burial and increase in temperature bring about physical and chemical changes called coalification. Because of… Read more →

The process of droplet growth as small drops merge together when they come in contact. If this occurs repeatedly, a continuous liquid phase forms. Through this phenomenon, emulsions break and form two distinct liquid… Read more →

Referring in the strict sense (API Bulletin 13C) to any particle larger than 2000 microns. Read more →

Any thin material, liquid or powder, which, applied over a structure, forms a continuous film to protect against corrosion.Corrosion coatings should possess flexibility, resistance against impact and moisture, good… Read more →

What Is a Coating Flaw? Coating flaw (also called a holiday) is a defect in the external protective coating of a buried or submerged pipeline — including pinholes, cracks, disbondment zones, or bare metal spots — that… Read more →

The characteristics of the trace used to display a log. The most common codings are solid, long-dashed, short-dashed and dotted. The trace can also have a different line weight or thickness, from light to heavy. Read more →

The process of generating two or more forms of energy from a single energy source. For example, in a heavy oilfield, turbines are often used to generate electricity while their waste heat is removed to generate steam.… Read more →

A quantitative assessment of the similarity of three or more functions, also called semblance. Read more →

A technique for removing noise and emphasizing coherent events from multiple channels of seismic data. Read more →

(noun) A seismic attribute display that measures the trace-to-trace similarity of seismic waveforms across a survey area. Areas of low coherence indicate discontinuities such as faults, fractures, stratigraphic edges,… Read more →

A map that displays the degree of correlation between wells as a vector that points from one well to another, the length of the vector being related to the degree of correlation from a correlogram. These maps are used… Read more →

Pertaining to seismic events that show continuity from trace to trace. Seismic processing to enhance recognition of coherent events and emphasize discontinuities such as faults and stratigraphic changes has gained… Read more →

Undesirable seismic energy that shows consistent phase from trace to trace, such as ground roll and multiples. Read more →

A technique for acquiring full-azimuthmarineseismic data. This technique uses a vessel equipped with source arrays and streamers to shoot and record seismic data; however, unlike conventional surveys acquired in a… Read more →

What Is Coiled Tubing? Coiled tubing is a continuous length of small-diameter steel or composite tubing (25 to 114 mm / 1 to 4.5 inches) wound on a large surface reel and deployed into wells under live wellbore pressure… Read more →

What Is a Coiled Tubing Completion? Coiled tubing completion (also called CT completion or coil-deployed completion) is a well completion technique in which a continuous coiled tubing string serves as the production… Read more →

What Is a Coiled Tubing Connector? Coiled tubing connector (also called CT bottom connector, CT BHA connector, or end fitting sub) is the threaded or hydraulically-activated fitting at the lower end of the coiled tubing… Read more →

What Is Coiled Tubing Drilling? Coiled tubing drilling (CTD) is a drilling technique that uses a continuous string of small-diameter — typically 2-3/8" to 3-1/2" OD — coiled tubing to convey a positive displacement… Read more →

What Is a Coiled Tubing String? Coiled tubing string (also called CT string or CT pipe) is the continuous, unjointed steel tube — typically 1 inch to 4-1/2 inches OD with wall thicknesses from 0.087 to 0.300 inches —… Read more →