Oil & Gas Glossary 1.0

In general, the higher the valence of an ion, the greater the loss of stability to emulsions, colloidal suspensions, etc., these polyvalent ions will impart

The added effect produced by two processes working in combination. It is greater than the sum of the individual parts.

Monovalent. See valence, unloader. Same as a circulation valve

The tendency of elements to form compounds through a shift of electronic structure.

Icing of equipment due to the cooling effect of expanding gas.

One of the alkali metal elements with a valence of 1, an atomic number of about 23. Numerous sodium compounds are used as additives to drilling fluids.

One of the alkaline earth elements with a valence of 2 and an atomic weight of about 40. Calcium compounds are a common cause of water hardness. Calcium is also a component of lime, gypsum, and limestone.

A remedial well-servicing activity whereby a cement slurry is pumped into open perfs, split casing, etc., to effect a blockage.

One of the alkali metal elements with a valence of 1 and an atomic weight of about 39. Potassium compounds, most commonly potassium hydroxide (KOH), are sometimes added to drilling fluids to impart special properties, usually inhibition.

The atomic or formula weight of an element, compound, or ion divided by its valence. Elements entering into combination always do so in quantities proportional to their equivalent weights.

A compound in which chromium has a valence of 6. Chromate may be added to drilling fluids either directly or as a constituent of chrome lignites or chrome lignosulfonates. In certain areas, chromate is widely used as a corrosion inhibitor, often in conjunction with lime.

A phenomenon in which a pressure concession occurs by suddenly stopping the flow of liquids in a closed container. Also called water hammer.

Any equipment designed to be pumped down a completed well to effect a repair, modify the well's flow, or for other reasons.

An acid that has been chemically treated before the acidizing or acid fracturing of a well to lessen its corrosive effect on the tubular goods and yet maintain its effectiveness. See acid fracture, acidize.

A heavy, thick-walled tube, usually steel, used between the drill pipe and the bit in the drill stem to provide a pendulum effect to the drill stem and weight to the bit.

(n) a device with an elastomer packing element that depends on pressure below the packing to effect a seal in the annulus. Used primarily to run or pull pipe under low or moderate pressures. This device is not dependable for service under high differential pressures. Also called a stripper.

2. the pressure drop from the outer limits of drainage to the wellbore caused by the relatively thin veneer (or skin) of the affected formation. Skin is expressed in dimensionless units: a positive value denotes formation damage; a negative value indicate improvement. Also called skin effect.

An instrument that measures fluid pressure and usually registers the difference between atmospheric pressure and the pressure of the fluid by indicating the effect of such pressures on a measuring element (e.g., a column of liquid, pressure in a Bourdon tube, a weighted piston, or a diaphragm).

A drilling mud prepared by adding a surfactant to a water-base mud to change the colloidal state of the clay from that of complete dispersion to one of controlled flocculation. Such muds were originally designed for use in deep, high-temperature wells, but their many advantages (high chemical and thermal stability, minimum swelling effect on clay-bearing zones, lower plastic viscosity, and so on) extend their applicability.

1. to force pipe or tools into a high-pressure well that has not been killed (i.e., to run pipe or tools into the well against pressure when the weight of pipe is not great enough to force the pipe through the BOPs). Snubbing usually requires an array of wireline bocks and wire rope that forces the pipe or tools into the well through a stripper head or blowout preventer until the weight of the string is sufficient to overcome the lifting effect of the well pressure on the pipe in the preventer. In workover operations, snubbing is usually accomplished by using hydraulic power to force the pipe through the stripping head or blowout preventer.