C

C-store
Convenience store.

Cap Rock
An impervious layer of rock that overlies a reservoir rock, thus preventing hydro- carbons from escaping to the surface.

Capillaries
The minute spaces, cracks or pores in rock through which hydrocarbon fluids move in response to natural forces.

Capping
Tightly closing a well so that oil or natural gas cannot escape.

Carbon
The base of all hydrocarbons; capable of combining with hydrogen in almost numberless hydrocarbon compounds. The carbon content of a hydrocarbon determines, to a degree, the hydrocarbon's burning characteristics and qualities.

Casing
Steel pipe that is cemented into a well to prevent the well bore wall from caving in, to stop drilling fluids from losing circulation and to prevent water and other fluids from invading the well bore.

Casing Perforation
The holes made in the liner of a finished well to allow oil or natural gas to flow into the production tube.

Casing Seat
The lowest point at which casing is set.

Casinghead
The top of the casing set in the well; the part of the casing that protrudes above the surface and to which the control valves and flow pipes are attached.

Casinghead Gas
Gas produced with oil from an oil well as distinguished from gas from a gas well. The casinghead gas is taken off at the top of the well or at the separator.

Casinghead Gasoline
Liquid hydrocarbons separated from casinghead gas by the reduction of pressure at the wellhead or by a separator or an absorption plant.

Catalyst
Substance that aids or promotes a chemical reaction between other substances, but does not, itself, enter into the reaction.

Catalytic Cracking
A petroleum refining process in which heavy hydrocarbon molecules are broken down (cracked) into lighter molecules by passing them over a suitable catalyst (generally heated).

Catalytic reforming 
The conversion of naphtha into higher octane intermediate products suitable for blending into finished gasoline or for petrochemical feedstocks via simultaneous catalytic combination of polymerisation, cracking, dehydrogeneration and isomerisation processes.

CCR (continuous catalyst regeneration)
Continuous catalyst regeneration technology. This assures the continuous operation of the catalytic reforming process. It involves partially aged catalyst in the reactors being continuously replaced with freshly generated catalyst from an external regenerator to maintain a low average cost of the reactor catalyst.

Cementing
The technique of pumping cement into the space between the casing and the well bore wall in order to hold the casing in place.

Choke
A device to restrict the rate of flow during the testing of an exploratory discovery.

CIF
CIF prices for crude oil, feedstocks and finished products include the cost of insurance and freight charges.

Circulation
The techniques for bringing rock cuttings from the bottom of the well bore to the surface by continuously pumping drilling mud down through the drill string and up the annulus during rotary drilling.

Clean Circulation
Descriptive of drilling muds returning to the surface without rock cuttings.

Closed-in
Descriptive of a well that is capable of producing, but is not producing at the time.

Coal
A solid fossil fuel consisting mainly of carbon produced by the compression of decayed plants.

Coalbed Methane
A methane-rich, sulfur-free natural gas contained within underground coal beds. Produced in the San Juan Basin of New Mexico.

Cogeneration
The simultaneous production of electricity and steam from a single process, which requires up to one-third less fuel than separate production.

Coke
Hard carbon and other crude oil impurities that can form inside furnace tubes.

Combined cycle power generation 
Electrical power generation using the combination of gas turbogenerators and steam turbogenerators. The flue gas from the gas turbogenerator's exhaust is used to produce steam to drive the steam turbogenerators.

Commercial Field
An oil or natural gas field that, under existing economic and operating conditions, is judged to be capable of generating enough revenues to exceed the costs of development.

Commingling
Producing oil and gas from two or more reservoirs at different depths.

Completing a Well
The process by which a finished well is either sealed off or prepared for production by fitting a wellhead.

Complex refinery 
A refinery, the configuration of which includes a cracking complex.

Concession
A geographic area that is licensed or leased to a company for a given period for exploration and development under specified terms and conditions.

Condensate
A term used to describe light liquid hydrocarbons separated from crude oil after production and sold separately.

Configuration index
A scale providing a quantitative means of comparing the overall processing capabilities of individual refineries. Configuration (or complexity) indices are produced by various companies (e.g., Solomon Associates).

Conservation
Regulation of oil and/or gas production from a reservoir in order to prolong its life and hopefully recover a larger quantity of the oil or gas in place; re-injection of associated gas for future use. Also, environmental protection and preservation.

Consortium
A group of unrelated companies acting together in a specific venture.

Continental Shelf
The edge of a continental mass that lies under the sea in comparatively shallow water (up to a water depth of about 800 feet).

Copolymer
A polymer manufactured from two or more different monomers. An example is butadiene-styrene.

Co-venturer
A person or company joined with others in a particular venture.

Cracking
The refinery process in which large, heavy, complex hydrocarbon molecules are broken down into simpler and lighter molecules in order to derive a variety of fuel products.

Crude Oil
A mineral oil consisting of a mixture of hydrocarbons of natural origin, yellow to black in color, of variable specific gravity and viscosity; often referred to simply as crude.

Crude slate sulphur content
The average percentage of sulphur contained in crude oil. Generally, the higher the crude slate content the lower the price of the crude oil.

Cyclohexane
The cyclic form of hexane; used as a raw material in the manufacture of nylon.