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An MWD downhole tool is also "high-sided" with the bottom hole drilling assembly, enabling the wellbore to be steered in a chosen direction in 3D space known as directional drilling. Directional drillers rely on receiving accurate, quality tested data from the MWD operator to allow them to keep the well safely on the planned trajectory.
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 ...
Modern techniques now permit continuous information at the surface. This is known as logging while drilling (LWD) or measurement-while-drilling (MWD). MWD logs use mud pulse technology to transmit data from the tools on the bottom of the drillstring to the processors at the surface.
AADE – American Association of Drilling Engineers [1] AAPG – American Association of Petroleum Geologists [2] AAPL – American Association of Professional Landmen; AAODC – American Association of Oilwell Drilling Contractors (obsolete; superseded by IADC) AAV – Annulus access valve; ABAN – Abandonment, (also as AB and ABD and ABND)
They are generally programmed by the measurement while drilling (MWD) engineer or directional driller who transmits commands using surface equipment (typically using either pressure fluctuations in the mud column or variations in the drill string rotation) which the tool responds to, and gradually steers into the desired direction.
Because of the lag time between drilling and the time required for the mud and cuttings to return to the surface, a modern augmentation has come into use: Measurement while drilling. The MWD technician, often a separate service company employee, logs data in a similar manner but the data is different in source and content.
In the process of drilling a borehole, geosteering is the act of adjusting the borehole position (inclination and azimuth angles) on the fly to reach one or more geological targets. These changes are based on geological information gathered while drilling. Originally only a projected target would be aimed for with crude directional tools.
The borehole can also change to an oval shape while drilling, which typically occurs in doglegs where the axis of borehole is bending to change the direction of the well. This oval shape can cause a 2-arm caliper log to overestimate the size of the borehole, if its arms get stuck in the long-axis.