Oil & Gas Glossary 1.0

2. a group of hydrous aluminum silicate minerals (clay minerals)

3. a sediment of fine clastics.

The replacement of cations associated with the clay surface by those of another species, e.g., the conversion of sodium clay to calcium clay.

A clay to which an agent has been added to increase its initial yield

A classification of commercial drilling-clay preparations having a yield of 35 to 40 barrels per ton and intermediate between bentonite and low-yield clays. Usually prepared by peptizing low-yield calcium montmorillonite clays or, in a few cases, by blending some bentonite with the peptized low yield clay

Any of several substances--usually organic compounds of high molecular weight--that, when added in low concentrations to a bentonite or to certain other clay slurries, will increase the viscosity of the system. See low-solids mud.

Commercial clay chiefly of the calcium montmorillonite type and having a yield of approximately 15 barrels per ton.

Commercial clay chiefly of the calcium montmorillonite type and having a yield of approximately 15 barrels per ton.

2. a group of hydrous aluminum silicate minerals (clay minerals)

A term used to define the quality of a clay by describing the number of barrels of a given centipoise slurry that can be made from a ton of clay. Based on the yield, clays are classified as bentonite, high yield, low yield, etc., types of clays. Not related to yield value below. See API RP 13B for procedures.

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.

See attapulgite

3. a sediment of fine clastics.

Any relatively sticky formation (such as clay) encountered in drilling

1. a term used for particles smaller than 1/256 millimeter (4 microns) in size, regardless of mineral composition.

A drilling fluid containing essentially clay and water; no special or expensive chemicals or conditioners are added.

To add solid materials (such as bentonite or other clay) to a drilling fluid composed mainly of clear water to obtain certain desirable properties.

A phenomenon that sometimes occurs when a well blows out. Rocks, sand, clay, and other debris clog the hole and stop the blowout.

A condition in which clay platelets remain stacked by a polyvalent cation, such as calcium, and are deflocculated by use of a thinner.

A clay mineral often used as an additive to drilling mud. It is a hydrous aluminum silicate capable of reacting with such substances of magnesium and calcium. See bentonite.

A water-base clay mud containing caustic soda and tannates to which lime has been added. Also called red mud.

The cement most widely used in oilwells. It is made from raw materials such as limestone, clay or shale, and iron ore.

That part of a drilling mud--clay, shale, barite, and other solids--that is dispersed throughout a liquid or gaseous medium, forming the mud.

A colloidal clay, composed primarily of montmorillonite, that swells when wet. Because of its gel forming properties, bentonite is a major component of water-based drilling muds. See gel, mud.

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

A fine-grained sedimentary rock composed mostly of consolidated clay or mud. Shale is the most frequently occurring sedimentary rock.

Circulating fluid, one function of which is to force cuttings out of the wellbore and to the surface. Other functions are to cool the bit and to counteract downhole formation pressure. While a mixture of barite, clay, water, and chemical additives is the most common drilling fluid, wells can also be drilled by using air, gas, water, or oil-base mud as the drilling fluid. See mud.

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.