A block with lead or another relatively soft material on its bottom. it is made up of drill pipe or tubing at the surface, run into a well, and set down on the object that has been lost in the well. the block is retrieved and the impression is examined. the impression is a mirror [...]

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 arrangement of pulleys, or sheaves, through which drilling line is reeved and which moves up and down in the derrick or mast. see block.

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

An assembly of pulleys on a common framework; in mechanics, one or more pulleys, or sheaves, mounted to rotate on a common axis. the crown block is an assembly of sheaves mounted on beams at the top of the derrick. the drilling line is reeved over the sheaves of the crown block alternately which the [...]

A displacement. in the reservoir a sweep is displacement of a hydrocarbon fluid from a reservoir rock by a flooding fluid. in the wellbore, a sweep is a viscous pill circulated around to help clear the wellbore of cuttings or debris.

A downhole device that isolates wellbore pressure and fluids in the event of an emergency or catastrophic failure of surface equipment. the control systems associated with safety valves are generally set in a fail-safe mode, such that any interruption or malfunction of the system will result in the safety valve closing to render the well safe. downhole [...]

A part of the brake mechanism consisting of a flexible steel band lined with a material that grips a drum when tightened. on a drilling rig, the brake band acts on the flanges of the drawworks drum to control the lowering of the traveling block and its load of drill pipe, casing, or tubing.

The set of pulleys or sheaves at the top of the mast on a rig.

A rotary tool that is hung from the rotary hook and traveling block to suspend the drill stem and to permit it to rotate freely. it also provides a connection fore the rotary hose and a passageway of the flow of drilling fluid into the drill stem.

Abbr. installation / workover control system
find more info about iwocs at hydrafit-subsea.co.uk

The amount of the pore volume of a reservoir rock that is filled by water, oil, or gas and measured in routine core analysis.

1. a scale of pressure differences in which there is a uniform variation of pressure from point to point. for example, the pressure gradient of a column of water is about 0.433 pounds per square inch per foot (9.794 kilopascals per meter) of vertical elevation. the normal pressure gradient in a formation is equivalent to [...]

See production rig. also see pulling unit.

Water that contains relatively low concentrations of soluble salts. brackish water is saltier than fresh water but not as salty as salt water.