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

To perform one or more of a variety of remedial operations on a producing oil well to try to increase production. examples of workover opera6tions are deepening, plugging back, pulling and resetting liners, squeeze cementing, and so on.

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 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.

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

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 [...]

See production rig. also see pulling unit.

Adding new wells in an existing field within the original well patterns to accelerate recovery or to test recovery methods.

A long steel casing that uses an inclined plane to cause the bit to deflect from the original borehole at a slight angle. whipstocks are sometimes used in controlled directional drilling, in straightening crooked boreholes, and in sidetracking to avoid unretrieved fish.

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.

Workover equipment designed in equipment packages or modules that are light enough to be lifted onto an offshore platform by a platform crane. in most cases, the maximum weight of a module of 12,000 pounds. once lifted from the work boat, the rig can be erected and working within twenty-four to thirty-six hours.

A series of hydraulic rams to restrain and pull tubing under well pressure, temporarily attached to the wellhead for workover.

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 [...]

A driller, a derrickman, and two or more helpers who operate a drilling or workover rig for one tour each day.