B
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barefoot completion |
See openhole completion. |
barite |
BaSO4. A natural mineral used as weighting material in drilling mud. |
barrel |
Petroleum barrel. A unit of measure for crude oil and oil products equal to 42 U.S. gallons. |
basalt |
A fine-grained, sometimes glassy basic igneous rock |
base-line shift |
Generally refers to a naturally occurring shift of the base line of any specific curve; e.g., the SP curve. Usually the base line referred to is the shale base line, but could be the sand base line or other base line. |
basement |
Usually synonymous with the Precambrian but the term may also be applied to any widespread association of igneous and metamorphic rocks which are covered unconformity by unmetamorphosed sediments |
basin |
A depression of large size, which maybe of structural or erosional origin |
bed |
A subdivision of a stratified sequence of rocks, lower in rank than a member or formation, internally composed of relatively homogeneous material exhibiting some degree of lithologic unity, and separated from the rocks above and below by visually or physically more or less well defined boundary planes. |
bedding planes |
In sedimentary or stratified rocks, the division planes that separate the individual layers, beds, or strata. |
bedrock |
A mining term for the unweathered rock below soil and drift cover. |
bed thickness |
(1) True bed thickness is the thickness of the stratigraphic unit measured along a line normal to the direction of extension of the unit. True thickness can be derived from information determined by the dipmeter. |
bentonite |
A colloidal clay, composed of montmorillonite, which swells when wet. Because of its gel-forming properties, bentonite is a major component of drilling muds. |
bit |
A cutting device attached to the bottom end of the drill pipe. Its function is to perform the actual boring or drilling of the rock formations. |
blind ram |
An integral part of a blow-out preventer, serving as the closing element. Its ends do not fit around the drill pipe but seal against each other and shut off the space below completely. |
blowout |
A sudden, uncontrolled flow of drilling fluid, oil, gas, or water from a wellbore when the formation pressure in a permeable formation exceeds the pressure in the borehole. A kick sometimes warns of low pressure in the borehole. |
blowout preventer |
BOP. A safety device for closing the wellhead, which has rubber rams which can be closed down on the logging cable in the event the well begins to blow out. Blow-out preventers may be connected in series for improved control. |
borehole |
The hole made by the drill bit |
borehole compensated sonic log |
The borehole compensated sonic sonde carries two sets of transducers, one with its transmitter above its receiver pair and one with its transmitter below. The transmitters are pulsed alternately, and the alternate measurements are averaged. Spurious effects caused by borehole-size changes, and sonde tilt, which would affect a measurement with a single set of transducers, are thereby substantially reduced. |
borehole effect |
The spurious influence on a well-logging measurement due to the influence of the borehole environment; e.g., diameter, shape, rugosity of the wall of the borehole, type of borehole fluid, and presence of mud cake. |
bound water |
(1) Water which has become adsorbed to the surfaces of solid particles or grains. Under natural conditions, this water is viscous like and immobile but might not have lost its electrolytic properties. See also adsorption and water wet. |
brackish water |
Water that contains relatively low concentrations of any soluble salts. Brackish water is saltier than fresh. |
break circulation |
To start the mud pump to restore circulation of the mud column. Because stagnant drilling fluid gels during the period of no circulation, a high pump pressure is usually required to break circulation. |
breccia |
One of the 2 main types of rudaceous rocks, consisting of angular fragments implying minimum transport of material. |
bridge plug |
A downhole device composed primarily of slips, a plug mandrel. and a rubber sealing element, that is run and set in casing to isolate a lower zone while testing an upper section. |
bridle |
The disconnectable, rubber insulation-covered downhole end of a survey cable on which current and measure electrodes (cable electrodes) are mounted for resistivity measuring electrode configurations requiring longer spacings than can be attained on a sonde. The head, to which the sonde is attached, is an integral part of the fishing bell and bridle. |
brine |
A highly saline solution. A solution containing appreciable amounts of NaCl and other salts. |
bubble flow |
A flow regime in which relatively uniform bubbles of gas or oil, approximately homogeneously distributed, flow upward through oil or water at a constant rate. The relative velocity is governed mainly by the difference between the densities of the lighter and heavier phases, and the viscosity of the heavier phase. |
bubble-point pressure |
The pressure at which gas first begins to come out of solution at constant temperature. |
bucking electrodes |
Current electrodes on a laterolog type resistivity measuring system from which bucking current flows in order to confine the survey current into a thin, horizontal investigative layer. Serve the same purpose as guard electrodes except bucking electrodes are usually rings or point electrodes (e.g., buttons). See laterolog. |
bulk density |
In well logging, it is the density of the rock with the pore volume filled with fluid. |
bulk volume water |
The quantity of formation water present in a unit volume of rock. The product of water saturation and porosity. |
bullet |
(1) A hollow projectile used for obtaining percussion sidewall cores. |
bull head |
To forcibly pump fluids into a formation, usually formation fluids that have entered the wellbore during a well control event. Though bullheading is intrinsically risky, it is performed if the formation fluids are suspected to contain hydrogen sulfide gas to prevent the toxic gas from reaching the surface. Bullheading is also performed if normal circulation cannot occur, such as after a borehole collapse. The primary risk in bullheading is that the drilling crew has no control over where the fluid goes and the fluid being pumped downhole usually enters the weakest formation. In addition, if only shallow casing is cemented in the well, the bullheading operation can cause wellbore fluids to broach around the casing shoe and reach the surface. This broaching to the surface has the effect of fluidizing and destabilizing the soil (or the subsea floor), and can lead to the formation of a crater and loss of equipment and life. |
bull plug |
A threaded nipple with a rounded, closed end with O-ring seals. Commonly used to plug off the bottom end of downhole logging instruments from borehole fluids. Some logging tools, which can be used jointly in tandem, require a bull plug for a seal when used independently. |
button |
A small disc-shaped, button-like electrode used on microresistivity pads. |
