A valve that will open automatically when pressure gets too high.

A system of controls, convenient to the driller, which can be used selectively to actuate valves at the master control panel.

The ratio of effective permeability to absolute permeability.

The relative permeability of rock to a single fluid is 1.0 when only that fluid is present, and 0.0 when the presence of another fluid prevents all flow of the given fluid.

Compare absolute permeability, effective permeability.

See red-lime mud.

To string a wire rope drilling line through the sheaves of the traveling and crown blocks to the hoisting drum.

See ram blowout preventer.

Two or more atoms behaving as a single chemical unit, i.e., as an atom, e.g., sulfate, phosphate, nitrate.

1.

A hole in the rig floor, 30 to 35 feet (9 to 11 meters) deep, which is lined with casing that projects above the floor and into which the kelly and swivel are placed when hoisting operations are in progress.

2.

A hole of a diameter smaller than the main hole and drilled in the bottom of the main hole.

v: to reduce the size of the wellbore and drill ahead.

A pump consisting of a piston that moves back and forth or up and down in a cylinder.

The cylinder is equipped with inlet (suction) and outlet (discharge) valves.

On the intake stroke, the suction valves are opened, and fluid is drawn into the cylinder.

On the discharge stroke, the suction valves close, the discharge valves open, and fluid is forced out of the cylinder.

A tool used in drilling to smooth the wall of a well, enlarge the hole to the specified size, help stabilize the bit, straighten the wellbore if kinks or doglegs are encountered, and rill directionally.

See ream.

In sucker rod pumping, the difference between the polished rod peak load on the upstroke and the minimum load on the downstroke.

To enlarge the wellbore by drilling it again with a special bit.

Often a rathole is reamed or opened to the same size as the main wellbore.

See rathole.

Abbreviation: radioactive densiometer; fluid-measuring device to measure density.

Rate (commonly given in rpm) at which an action resulting from applied forces causes or tends to cause two adjacent parts of a body to slide relative to each other in a direction parallel to their plane of contact.

After the initial completion of a well, the action and techniques of reentering the well and redoing or repairing the original completion to restore the well’s productivity.