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Well logging, also known as borehole logging is the practice of making a detailed record (a well log) of the geologic formations penetrated by a borehole.The log may be based either on visual inspection of samples brought to the surface (geological logs) or on physical measurements made by instruments lowered into the hole (geophysical logs).
A drilling rig is used to create a borehole or well (also called a wellbore) in the earth's sub-surface, for example in order to extract natural resources such as gas or oil. During such drilling, data is acquired from the drilling rig sensors for a range of purposes such as: decision-support to monitor and manage the smooth operation of ...
Mud logging is usually performed by a third-party mud logging company. This provides well owners and producers with information about the lithology and fluid content of the borehole while drilling. Historically it is the earliest type of well log. Under some circumstances compressed air is employed as a circulating fluid, rather than mud.
Logging while drilling (LWD) is a technique of conveying well logging tools into the well borehole downhole as part of the bottom hole assembly (BHA).. Although the terms Measurement while drilling (MWD) and LWD are related, within the context of this section, the term MWD refers to directional-drilling measurements, e.g., for decision support for the smooth operation of the drilling, while ...
Resistivity logging is used in mineral exploration (for example for exploration for iron and copper ore bodies), geological exploration (deep geological disposal, geothermal wells), and water-well drilling. It is an indispensable tool for formation evaluation in oil- and gas-well drilling.
The written strip chart recording of these examinations is called a sample log or mudlog. Well cuttings examination is a learned skill. During drilling, chips of rock, usually less than about 1 ⁄ 8 inch (3.2 mm) across, are cut from the bottom of the hole by the bit. Mud, jetting out of holes in the bit under high pressure, washes the ...
The drill cuttings are commonly examined to make a record (a well log) of the subsurface materials penetrated at various depths. In the oil industry, this is often called a mud log . Drill cuttings are produced as the rock is broken by the drill bit advancing through the rock or soil; the cuttings are usually carried to the surface by drilling ...
A caliper log is a well logging tool that provides a continuous measurement of the size and shape of a borehole along its depth [1] and is commonly used in hydrocarbon exploration. The measurements that are recorded can be an important indicator of wash-outs, cave ins or shale swelling in the borehole, which can affect the results of other well ...