Oil and Gas Terms Beginning with “C” — Page 11

The reciprocal of resistance in a direct current circuit, measured in siemens (formerly mhos). In an alternating current circuit, conductance is the resistance divided by the square of impedance, also measured in… Read more →

A situation in which the resistivity of the flushed zone is less than the resistivity of the undisturbed zone. Such a setting generally favors the use of electrode resistivity devices (laterologs, ring resistivity),… Read more →

A model, or set of equations, for the resistivity response of formations with conductive minerals, such as shaly sands. The model is used to analyze core data and to calculate water saturation from resistivity and other… Read more →

The ability of a material to conduct electricity. It is the inverse of resistivity and is measured in siemens per meter (S/m) or mho/m. The conductivity is a property of the material, whereas the conductance also… Read more →

A technique for estimating the cation-exchange capacity of a sample by measuring the conductivity of the sample during titration. The technique includes crushing a core sample and mixing it for some time in a solution… Read more →

A short string of large-diameter casing set to support the surface formations. The conductor pipe is typically set soon after drilling has commenced since the unconsolidated shallow formations can quickly wash out or… Read more →

The nature of the contact between strata deposited in continuous succession. Read more →

A bedding surface separating younger from older strata, along which there is no evidence of subaerial or submarine erosion or of nondeposition, and along which there is no evidence of a significant hiatus.… Read more →

A projection of data from the apex of a cone in a three-dimensional plot onto a surface at the base of the cone. This projection often is performed in log analysis to remove a dimension and see what a data point would… Read more →

What Is Coning? Coning is the upward encroachment of water or downward migration of gas into the wellbore of an oil producer, caused by the pressure sink created by the producing well. In a layered reservoir where oil… Read more →

Water trapped in the pores of a rock during formation of the rock. The chemistry of connate water can change in composition throughout the history of the rock. Connate water can be dense and saline compared with… Read more →

The act of adding a joint or stand of drillpipe to the top of the drillstring, also described as "making a connection." Read more →

A brief influx of gas that is introduced into the drilling fluid when a pipe connection is made. Before making a connection, the driller stops the mud pumps, thereby allowing gas to enter the wellbore at depth. Gas may… Read more →

A rheological property of matter related to the cohesion of the individual particles of a given material, its ability to deform and its resistance to flow. The consistency of cementslurries is determined by thickening… Read more →

A laboratory device used to determine the thickening time of cementslurries under simulated downhole pressure and temperature conditions. Read more →

Pertaining to sediments that have been compacted and cemented to the degree that they become coherent, relatively solid rock. Typical consequences of consolidation include an increase in density and acoustic velocity,… Read more →

A laboratory test usually performed as part of a routine PVT analysis that measures the change in volume of a reservoir fluid as a function of pressure. This change is determined by measuring the total volume of a… Read more →

A flow rate that does not change appreciably during a test period. Flow rates are never truly constant, but changes of only a few percent do not affect the results of well-test analysis appreciably if the rate is… Read more →

The angle of intersection of the interface between two fluids at a solid surface. The angle is measured from the solid surface through the aqueous phase, or in an oil and gas test through the oil phase. The contact… Read more →

The elapsed time required for a specific fluid to pass a designated depth or point in the annulus during pumping operations. Contact time is normally used as a design criterion for mud removal in turbulent flow. Read more →

A chemical or fluid that alters the performance of an engineered slurry or treatment fluid. Some remedial cementing treatments require unpredictable volumes of cement slurry to achieve the desired results. When excess… Read more →

Gas that is introduced into the drilling mud from a source other than the formation. Contamination gas normally evolves as a by-product of oil-base mud systems and those using volatile additives such as diesel fuel or… Read more →

A key component of the operational planning process that takes account of reasonably foreseeable events that may prevent completion of normal operations. The formal plans and procedures for any operation should include… Read more →

Material balance expressed in a differential equation. Read more →

An artificial-lift method in which the gas-lift system is operated on a continuous basis to sustain liquid production at an efficient rate. Read more →

A type of areally extensive reservoir that contains hydrocarbon throughout, rather than containing a water contact or being significantly affected by a water column or a defined structuralclosure. The areal extent of a… Read more →

(noun) A line drawn on a map connecting points of equal value for a given property, such as depth, thickness, pressure, porosity, or hydrocarbon saturation. Contour maps are fundamental tools in subsurface mapping for… Read more →

The value of the separation between two adjacent contours. A net pay isopachmap might have a contour interval of 10 feet [3 m], whereas a structurecontour map might have a contour interval of 1000 feet [300 m]. Contour… Read more →

A map displaying lines that include points of equal value and separate points of higher value from points of lower value. Common types of contour maps include topographic contour maps, which show the elevation of the… Read more →

The depth in a drilling well at which the drilling contractor receives a lump-sum payment for reaching a particular milestone. The contract depth is specified in a legal agreement between the operator, who pays for the… Read more →