Oil & Gas Terms in Category H

Heat (a connection)

To loosen a collar or other threaded connection by striking it with a hammer.


Of uniform or similar nature throughout; a substance or fluid with the same property or composition everywhere.



A chemical reaction in which molecular water is added to the molecule of another compound without breaking it down.


Reaction of powdered cement with water.

The cement gradually sets to a solid as hydration continues.

Hydraulic fracture

A fracture creased by hydraulic pressure, usually intentional.

High ph mud

A drilling fluid with a ph range above 10.5 i.e., a high-alkalinity mud.

Hydraulic workover

A series of hydraulic rams to restrain and pull tubing under well pressure, temporarily attached to the wellhead for workover.


A mechanical arrangement that prevents the upward movement of certain pieces of equipment installed in a well.

A sucker rod pump may use a mechanical hold-down for attachment to a seating nipple.

Hole opener

A device used to enlarge the size of an existing borehole, having teeth arranged on its outside circumference to cut the formation as it rotates.


The partial or complete collapse of the walls of a hole resulting from internal pressures due primarily to swelling from hydration or formation gas pressures.

See caving.

Hard water

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

Compare soft water.

Hanger plug

A device placed or hung in the casing below the blowout preventer stack to form a pressure tight seal.

Pressure is then applied to the blowout preventer stack to test it for leaks

Hydrostatic pressure

The force exerted by a body of fluid at rest.

It increases directly with the density and the depth of the fluid and is expressed in pounds per square inch or kilopascals.

The hydrostatic pressure of fresh water is 0.433 pounds per square inch per foot of depth (9.792 kilopascals per meter).

In drilling, the term refers to the pressure exerted by the drilling fluid in the wellbore.

In a water drive field, the term refers to the pressure that may furnish the primary energy for production.

Hot oil

Oil production in violation of state regulations or transported interstate in violation of federal regulations.

Half mule shoe

A cutoff pup joint below a packer used as a fluid entry device and/or seal assemblies guide


Container or vessel enclosing an arrangement of tubes and a firebox in which an emulsion is heated before further treating, or in which natural gas is heated in the field to prevent the formation of hydrates.