Drilling for oil or gas in an ocean, gulf, or sea, usually on the outer continental shelf. a drilling unit for offshore operations may be a mobile floating vessel with a ship or barge hull, a semisubmersible or submersible base, a self-propelled or towed structure with jacking legs (jackup drilling rig), or a permanent structure [...]

A specially compounded liquid circulated through the wellbore during rotary drilling operations. see mud.

1. intentional deviation of a wellbore from the vertical. although wellbores are normally drilled vertically, it is sometimes necessary or advantageous to drill at an angle from the vertical. controlled directional drilling makes is possible to reach subsurface areas laterally remote from the point where the bit enters the earth. it often involves the use [...]

A fitting placed in the blowout preventer stack to provide space between preventers for facilitating stripping operations, to permit attachment of choke and kill lines, and for localizing possible erosion by fluid flow to the spool instead of to the more expensive pieces of equipment.

An adaptive drilling process used to precisely control the annular pressure profile throughout the wellbore (iadc definition).

Drilling in which the size of the hole is smaller than the conventional hole diameter for a given depth. this decrease in hole size enables the operator to run smaller casing, thereby lessening the cost of completion. see miniaturized completion.

A lease or a number of leases of adjoining tracts of land that constitute a unit of acreage sufficient to justify the expense of drilling a wildcat.

1. a sudden increase in the drill bit’s rate of penetration. it sometimes indicates that the bit has penetrated a high-pressure zone and thus warns of the possibility of a kick.
2. a sudden increase in the rate of penetration during drilling. when this increase is significant (two or more times the normal speed, depending on local [...]

An individual or group of individuals that own a drilling rig and contract their services for drilling wells.

1. 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 [...]

The supervisor of drilling or workover operations on a rig. also called a rig manager, rig supervisor, rig superintendent, or tool pusher.

1. a short, heavy, cylindrical section of steel filled with concrete and rounded at the bottom, which is placed at the end of the casing string. it prevents the casing from snagging on irregularities in the borehole as it is lowered. a passage through the center of the shoe allow drilling fluid to pass up [...]

1. a short length of surface-hardened pipe that fits inside the swivel and serves as a conduit for drilling fluid through the swivel. 2. sometimes used to mean washover pipe.

A wire rope used to support the drilling tools. also called the rotary line.

A drilling technique whereby gases (typically compressed air or nitrogen) are used to cool the drill bit and lift cuttings out of the wellbore, instead of the more conventional use of liquids. the advantages of air drilling are that it is usually much faster than drilling with liquids and it may eliminate lost circulation problems. the disadvantages [...]