Oil & Gas Glossary 1.0

A dome that is caused by an intrusion of rock salt into overlying sediments. A piercement salt dome is one that has been pushed up so that it penetrates the overlying sediments, leaving them truncated. The formations above the salt plug are usually arched so that they dip in all directions away from the center of the dome, thus frequently forming traps for petroleum accumulations.

A compound that is formed (along with water) by the reaction of an add with a base. A common salt (table salt) is sodium chloride derived by combining hydrochloric add with sodium hydroxide. The result is sodium chloride and water. Another salt is calcium sulfate, obtained when sulfuric acid is combined with calcium hydroxide.

A geologic structure resembling an inverted bowl; a short anticline that plunges on all sides.

1. a drilling mud in which the water has an appreciable amount of salt (usually sodium or calcium chloride) dissolved in it. Also called saltwater mud or saline drilling fluid.

Water that has large quantity of salt, especially sodium chloride, dissolved in it, salt water.

A reservoir formation in which fluid or plastic masses of rock material originated at unknown depths and pierced or lifted the overlying sedimentary strata.

A substance capable of reacting with an acid to form a salt. A typical base is sodium hydroxide (caustic), with the chemical formula MOH. For example, sodium hydroxide combines with hydrochloric acid to form sodium chloride (a salt) and water.

See salt mud.

2. a salt or ester of phosphoric acid

An influx of formation salt water into the wellbore

Common table salt. It is sometimes used in cement slurries as an accelerator or a retarder, depending on the concentration.

A reaction in which the hydrogen ion of an acid and the hydroxyl ion of a base unite to form water, the other ionic product being salt.

1.a disk-like plate of anhydrite, gypsum, limestone, or sulfur overlying most salt domes in the Gulf Coast region.

An uncontrolled flow of gas, salt water, or other fluid out of the wellbore and into another formation that the wellbore has penetrated.

A well through which water (usually salt water) is returned to subsurface formations.

A solution that contains at a given temperature as much of a solute as it can retain. At 68 degrees F it takes 126.5 lb/bbl salt to saturate 1 bbl of fresh water. See supersaturation.

2. a mud with a resistivity less than or equal to the formation water resistivity.

The sodium or potassium salt of a high-molecular weight fatty acid. Commonly used in drilling fluids to improve lubrication, emulsification, sample size, and defoaming.

A very soluble salt used to increase the density of water to points more than double that of water. Normally added to a system first saturated with calcium chloride.

The half-neutralized sodium salt of carbonic acid, used extensively for treating cement contamination and occasionally other calcium contamination in drilling fluids.

Substances generally regarded as drilling mud contaminants, such as salt and calcium sulfate, are called inhibitors when purposely added to mud so that the filtrate from the drilling fluid will prevent or retard the hydration of formation clays shells.

A liquid, usually salt water or oil, but sometimes mud, used in a well when a packer is between the tubing and the casing. Packer fluid must be heavy enough to shut off the pressure of the formation being produced, must not stiffen or settle out of suspension over long periods of time, and must be noncorrosive.

Special class of inhibited chemical muds using as their bases sodium silicate, salt, water, and clay

Water that contains relatively low concentrations of soluble salts. Brackish water is saltier than fresh water but not as salty as salt water.

Salt of stearic acid that is a saturated, 18-carbon fatty acid. Certain compounds, such as aluminum stearate, calcium stearate, zinc stearate, have been used in drilling fluids for one or more of the following purposes: defoamer, lubrication, air drilling in which a small amount of water is encountered.

A method of killing a well that has kicked, in which the choke size is adjusted to maintain a constant casing pressure. This method does not work unless the kick is all or nearly all salt water. if the kick is gas, this method will not maintain a constant bottomhole pressure, because gas expands as it rises in the annulus. In any case, it is not a recommended well-control procedure.

1. a scale of pressure differences in which there is a uniform variation of pressure from point to point. For example, the pressure gradient of a column of water is about 0.433 pounds per square inch per foot (9.794 kilopascals per meter) of vertical elevation. The normal pressure gradient in a formation is equivalent to the pressure exerted at any given depth by a column of 10 percent salt water extending from that depth to the surface 0.465 pounds per square inch per foot or 10.518 kilopascals per meter).

A porous and permeable underground formation containing an individual and separate natural accumulation of producible hydrocarbons (oil and/or gas) which is confined by impermeable rock or water barriers and is characterized by a single natural pressure system. A subsurface, porous, permeable rock body in which oil and/or gas is stored, Most reservoir rocks are limestones, dolomites, sandstones, or a combination of these. The three basic types of hydrocarbon reservoirs are oil, gas, and condensate. An oil reservoir generally contains three fluids - gas, oil, and water - with oil the dominant product. In the typical oil reservoir, these fluids occur in different phases because of the variance in their gravities. Gas, the lightest, occupies the upper part of the reservoir rocks; water, the lower part; and oil, the intermediate section. In addition to its occurrence as a cap or in solution, gas may accumulate independently of the oil; if so, the reservoir is called a gas reservoir. Associated with the gas, in most instances, are salt water and some oil. In a condensate reservoir, the hydrocarbons may exist as a gas, but, when brought to the surface, some of the heavier ones condense to a liquid.