Mechanical Drift Recorder
Definition - What does Mechanical Drift Recorder mean?
A mechanical drift recorder is a device that is used to measure how much a borehole deviates from the vertical drill path. The drift recorder, which works like an inverted pendulum, is inserted into the drill string while attached to a wire or wireline unit to the bottom of the bore where it measures and records the angle of vertical departure in degrees (°). The device is then pulled back out of the borehole for operators to inspect and read the measurement.
A mechanical drift recorder is also known as a Totco or a Totco barrel.
Trenchlesspedia explains Mechanical Drift Recorder
Wellbore deviation results from external forces acting on the drill bit. These forces may be affected by formation characteristics, bit type, borehole angle, rotary speed, bit weight, and drill string mechanical properties.
To ensure that drilling goes according to the well plan, deviations surveys are periodically performed to measure the angle of the deviation of the drill string from the vertical alignment. Mechanical drift records are essential to these deviation surveys.
The mechanical drift recorders are used to take measurements at regular intervals to ensure that the borehole reaches the intended target and does not encroach on any property lines or hit any undesirable areas.