Oil & Gas Terms in Category L



Loss of energy.

Lost returns

See lost circulation.

Lower kelly cock n: see drill stem safety valve

Lost circulation material (lcm)

A substance added to cement slurries or drilling mud to prevent the loss of cement or mud to the formation.

See bridging materials.


abbr: logging while drilling.

Low-solids fluid

See low-solids mud

Low-solids mud

A drilling mud that contains a minimum amount of solid material (sand, silt, and so on) and that is used in rotary drilling when possible because it can provide fast drilling rates.

Lower crown plug (subsea)

A plug that fits in the bore of a subsea tree, usually below the tubing hanger, to serve as the primary barrier against reservoir pressure.


Liquefied petroleum gas

Lease separator

A facility located at the surface for the purpose of:

Lyohilic colloid

A colloid that is not easily precipitated from a solution and is readily dispersible after the precipitation by an addition of the solvent.


A person who negotiates with the land or mineral rights owner to secure a lease to drill.

Lyphobic colloid

A colloid that is readily precipitated from a solution and cannot be redispersed by an addition of the solution.



To apply grease or oil to moving parts


To lower or raise tools in or out of a well with pressure inside the well.

The term comes from the fact that a lubricant (grease) is often used to provide a seal against well pressure while allowing wireline to move in or out of the well.



Liquefied natural gas.


Having an affinity for the suspending medium, such as bentonite in water.