In a well-control operation, closing the bop without first opening an alternate flow path up the choke line. when the bop is closed, pressure in the annulus cannot be read on the casing pressure gauge. compare soft shut-in.

A milling device attached to the bottom of washpipe that mills or drills debris accumulated around the outside of the pipe being washed over. usually, a burn shoe has pieces of very hard tungsten carbide embedded in it. also called a rotary shoe. see washpipe.

A downhole tool with rough, sharp, extremely hard cutting surfaces for removing metal by grinding or cutting. mills are run on drill pipe or tubing to grind up debris in the hole, remove stuck portions of drill stem or sections of casing for sidetracking, and ream out tight spots in the casing. they are also [...]

A length of pipe whose bottom edge is serrated or dressed with a hard cutting material and that is run into the wellbore around the outside of stuck casing, pipe, or tubing to mill away the obstruction.

Water that contains dissolved compounds of calcium, magnesium, or both. compare soft water.

A formation where the velocity of the compressional wave traveling through the borehole fluid is less than the velocity of the shear wave through the surrounding formation. in such conditions a shear head wave is generated, so that standard techniques based on monopole transducers can be used to measure formation shear velocity.
in hard formations, several [...]

A fine, very hard, gray crystalline powder, a compound of tungsten and carbon. this compound is bonded with cobalt or nickel in cemented carbide compositions and used for cutting tools, abrasives, and dies.

A heavy coupling element for drill pipe. it is made of special ahoy steel and has coarse, tapered threads and seating shoulders designed to sustain the weight of the drill stem, withstand the strain of frequent coupling and uncoupling, and provide a leakproof seal. the male section of the joint, or the pin, is attached [...]

In well-control operations, closing the bop’s with the choke and hcr, or fail-safe, valves open. compare hard shut-in.

Water that is free of calcium or magnesium salts. compare hard water

To let a well flow at too high a rate.

A drilling bit with cutting edges of hard alloys. developed about 1900, and first used with the rotary system of drilling, it is still useful in drilling very soft formations. also called a drag bit.

A slip employing tungsten-carbide “buttons” in lieu of conventional wicker-type teeth to set tools in very hard casing.

The character or state of the drilling mud filter cake. from api rp 13b: notations such as “hard,” “soft,” “tough,” rubbery,” and “firm” may be used to convey some idea of cake consistency.

A chemical compound of calcium, sulfur, and oxygen. although sometimes considered a contaminant of drilling fluids, it may at times be added to them to produce certain properties. like calcium carbonate it forms scales in water-handling facilities, which may be hard to remove. see gypsum.