Dictionary:Measurement-while-drilling (MWD)

Bottomhole data are acquired incrementally from sensors located in the drill string near the bit in a drilling well. Measurements may include directional information (hole inclination, azimuth, tool facing), drilling parameters (bottomhole temperature, pressure, torque, weight-on-bit, RPM), rig safety data, formation evaluation and correlation data (formation resistivity, gamma-ray, and sonic logs). Data can be transmitted to the surface in real time by pressure pulses through the mud inside the drill pipe (timed amplitude and phase encoding). Telemetry by conductor cable integrated with the drill pipe or temporary digital recording at the sensor for later wire-line retrieval are alternative data recovery methods. Compare Tomex.