Oil & Gas Glossary 1.0

(slang) gypsum

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

A non-fermenting cellulose product used in drilling fluids to combat contamination from anhydrite (gypsum) and to lower the water loss of the mud.

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 chemical compound of calcium, sulfur, and oxygen. Although sometimes considered a contaminant of drilling fluids, it may at times be added to them to produce certain properties. Like calcium carbonate it forms scales in water-handling facilities, which may be hard to remove. See gypsum.

A naturally occurring crystalline form of calcium sulfate in which each molecule of calcium sulfate is combined with two molecules of water. See calcium sulfate.

Dissolved calcium ions in sufficient concentration to impart undesirable properties, such as flocculation, reduction in yield of bentonite, and increased fluid loss, in a drilling fluid. See also calcium carbonate, calcium sulfate, gypsum.

A freshwater drilling mud using calcium oxide (lime) or calcium sulfate (gypsum) to retard the hydrating qualities of shale and clay formation, thus facilitating drilling. Calcium-treated muds resist scale and any anhydrite contamination but may require further treatment to prevent gelation (solidifcation) under the high temperatures of deep wells.

A slurry of portland cement and water and sometimes one or more additives that affect either the density of the mixture or its setting time. The portland cement used may be high early strength common (standard), or slow setting. Additives include accelerators (such as calcium chloride), retarders (such as gypsum), weighting materials (such as barium sulfate), lightweight additives (such as bentonite), or a variety of lost circulation materials (such as mica flakes).