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.

Abbr.

Bottom hole assembly

(bha) the lower portion of the drillstring, consisting of (from the bottom up in a vertical well) the bit, bit sub, a mud motor (in certain cases), stabilizers, drill collars, heavy-weight drillpipe, jarring devices (“jars”) and crossovers for various threadforms.

The bottomhole assembly must provide force for the bit to break the rock (weight on bit), survive a hostile mechanical environment and provide the driller with directional control of the well.

Oftentimes the assembly includes a mud motor, directional drilling and measuring equipment, measurementswhile- drilling tools, logging-while-drilling tools and other specialized devices.

A simple bha consisting of a bit, various crossovers, and drill collars may be relatively inexpensive (less than $100,000 us in 1999), while a complex one may cost ten or more times that amount.

To use a mill to remove the outside area of a permanent downhole tool.

The fibrous, flaky, or granular material added to a cement slurry or drilling fluid to aid in sealing formations in which lost circulation has occurred.

See lost circulation, lost circulation material.

The number of centigrams of bromine that are absorbed by 1 gram of oil under certain conditions.

This is a test for the degree of unsaturatedness of a given oil.

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

1.

Forcing gas back into a formation by pumping into the annulus from the surface.

2.

Any pumping procedure in which fluid is pumped into the well against pressure.

3.

To forcibly pump fluids into a formation, usually formation fluids that have entered the wellbore during a well control event.

Though bullheading is intrinsically risky, it is performed if the formation fluids are suspected to contain hydrogen sulfide gas to prevent the toxic gas from reaching the surface.

Bullheading is also performed if normal circulation cannot occur, such as after a borehole collapse.

The primary risk in bullheading is that the drilling crew has no control over where the fluid goes and the fluid being pumped downhole usually enters the weakest formation.

In addition, if only shallow casing is cemented in the well, the bullheading operation can cause wellbore fluids to broach around the casing shoe and reach the surface.

This broaching to the surface has the effect of fluidizing and destabilizing the soil (or the subsea floor), and can lead to the formation of a crater and loss of equipment and life.

1.

A pipe fitting on which the external thread is larger than the internal thread to allow two pipes of different sizes to be connected.

2.

A removable lining or sleeve inserted or screwed into an opening to limit its size, resist wear or corrosion, or serve as a guide.

A nitrile rubber used throughout the oilfield as an elastometer seal, i.e., in o-rings, v-rings.

A percussion tool run on a fishing string to jar downward or upward on a stuck fish to knock it free.

The bumper sub body moves up and down on a mandrel.

To secure the wellhead or other components.

A paraffin hydrocarbon, a gas in atmospheric conditions but is easily liquefied under pressure.

It is a constituent of liquefied petroleum gas.

See commercial butane, field-grade butane, normal butane.

Any substance or combination of substances that, when dissolved in water, produces a solution that resists a change in its hydrogen ion concentration on the addition of acid or base.

The random movement exhibited by microscopic particles when suspended in liquids or gases.

It is caused by the impact of molecules of fluid surrounding the particle.