The depth of a well or features within the wellbore as measured while drilling. the measured length of each joint of drillpipe or tubing is added to provide a total depth or measurement to the point of interest. drillers depth is the first depth measurement of a wellbore and is taken from the rotary table level on [...]

A floating offshore drilling unit that has pontoons and columns that when flooded cause the unit to submerge in the water to a predetermined depth. living quarters, storage space, and so forth a reassembled on the deck. semisubmersible rigs are either self-propelled or towed to a drilling site and either anchored or dynamically positioned over [...]

A self-propelled floating offshore drilling unit that is a ship constructed to permit a well to e drilled from it. although not as stable as semisubmersible, drill ships are capable of drilling exploratory wells in deep, remote waters. see floating offshore drilling rig.

A self-propelled floating offshore drilling unit that is a ship constructed to permit a well to be drilled from it. while not as stable as semisubmersible, drill ships are capable of drilling exploratory wells in deep, remote waters. they may have a ship hull, a catamaran hull, or a trimaran hull. see floating offshore drilling [...]

A short subassembly used to enable two components with different thread types or sizes to be connected.
abbr. xo.

The gauge at the driller’s position that records data from the pit-level indicator.

The reservoir drive mechanism in which oil is produced by the expansion of the underlying water and rock, which forces the oil into the wellbore. in general, there are two types of water drive: bottom-water drive, in which the oil is totally underlain by water; and edgewater drive, in which only a portion of the [...]

The recording of the natural or induced radioactive characteristics of subsurface formations. a radioactivity log, also known as a radiation log or a nuclear log, normally consists of two recorded curves: a gamma ray curve and a neutron curve. both help to determine the types of rocks in the formation and the types of fluids [...]

The downhole assembly used to lift fluid to the surface by the reciprocating action of the sucker rod string. basic components are barrel, plunger, valves, and hold-down. two types of sucker rod pumps are the tubing pump, in which the barrel is attached to the tubing, and the rod, or insert, pump, which is run [...]

A two-parameter rheological model widely used in the drilling fluids industry to describe flow characteristics of many types of muds. fluids obeying this model are called bingham plastic fluids and exhibit a linear shear-stress, shear-rate behavior after an initial shear-stress threshold has been reached.

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 [...]

An instrument near the driller’s position on a drilling rig that shows both the weight of the drill stem that is hanging from the hook (hook load)

The recording of information about subsurface geologic formations, including records kept by the driller and records of mud and cutting analyses, core analysis, drill stem tests, and electric, acoustic, and radioactivity procedures. see acoustic log, core analysis, driller’s log, drill stem test, electric well log, mud analysis, and radioactivity well logging.

Used extensively for treating various types of calcium contamination. also called soda ash.

A porous and permeable underground formation containing an individual and separate natural accumulation of producible hydrocarbons (oil and/or gas) which is confined by impermeable rock or water barriers and is characterized by a single natural pressure system. a subsurface, porous, permeable rock body in which oil and/or gas is stored, most reservoir rocks are limestones, [...]