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lag |
The distance between the static measure point and the dynamic measure point of a logging measurement. For nuclear logs and any others that must be recorded over a significant time period, there is a difference between the measure point with the tool stationary and moving. If the tool is moving during this period, the effective centre of measurement will be a certain distance from the point at which the measurement started. This distance is the lag. The lag depends on the logging speed and the sampling interval |
lag time |
The time taken for cuttings to reach the surface The term is also used in place of cycle time. |
laminar |
In the form of a thin layer(s) of sedimentary rock which is of different mineralization or lithology and is visually separable from the host rock or other laminae. Laminae of sand or other permeable sediment sometime show unusually high productivity. Laminae of clay, sandwiched between layers of a host rock, not only support overburden but also take the place of some of the host rock and whatever porosity the host rock would contain. |
laminar flow |
Nonturbulent fluid flow. A smooth flow at relatively low velocity in which the fluid elements follow paths that are straight and are parallel to the channel walls. |
laterolog |
A resistivity log (run in uncased hole filled with electrically conductive mud) made with a tool that achieves focusing through the use of additional current electrodes above and below a central measure-current electrode. Bucking currents from the additional electrodes serve to confine the measure current to essentially a narrow disc of current flowing outwardly perpendicular to the sonde. Should the survey current tend to flow vertically in the mud column (because of highly resistive beds), currents from the symmetrically positioned bucking electrodes are caused to increase or decrease in order to maintain the horizontal attitude of the survey-current flow. |
limestone |
The term limestone is applied to any sedimentary rock consisting essentially of carbonates. The 2 most important constituents are calcite and dolomite, but small amounts of iron-bearing carbonates might also occur. |
liquefied natural gas |
LNG. A liquid composed chiefly of natural gas (i.e., mostly methane). Natural gas is liquefied to make it easier to transport if a pipeline is not feasible (as across a body of water). Not as easily liquefied as liquefied petroleum gas, LNG must be put under low temperature and high pressure to become liquefied. |
liquefied petroleum gas |
LPG. A mixture of heavier, gaseous, paraffinic hydrocarbons, principally butane and propane. These gases, easily liquefied at moderate pressures, may be transported as liquids but converted to gases on release of the pressure. Thus, liquefied petroleum gas is a portable source of thermal energy that finds wide application in areas where it is impracticable to distribute natural gas. It is also used as a fuel for internal-combustion engines and has many industrial and domestic uses. Principal sources are natural and refinery gas, from which the liquefied petroleum gases are separated by fractionation |
lithology |
A term usually applied to sediments, referring to their general characteristics. Lithology generally relates to descriptions based upon hand-specimen and outcrops rather than microscopic or chemical features |
lithostatic load |
The weight of the overlying rock column without the fluids contained in the pore volumes of the rock. |
live oil |
Oil that contains dissolved gas. |
log |
Well log. A record containing one or more curves related to properties in the well bore or some property in the formations surrounding the well bore. |
logging tool |
An openhole or cased-hole tool for performing downhole well log data gathering services for determining properties of the formation, or characteristics of the well bore environment. |
lost circulation |
The loss of quantities of mud to a formation, usually in cavernous, fissured, or coarsely permeable beds, evidenced by the complete or partial failure of the mud to return to the surface as it is being circulated in the hole. |
lost-circulation material |
A substance added to cement slurries or drilling muds to prevent the loss of cement or mud to the formation. |
lubricator |
Refers to the assembly of wireline pressure-control equipment consisting of blowout preventer, riser, flow tube, and stuffing box (or hydraulic packing head). |
