BOREHOLE DEPTH MEASUREMENT METHOD Russian patent published in 2006 - IPC E21B47/04 

FIELD: well drilling, particularly for measuring depth or liquid level in borehole.

SUBSTANCE: method involves arranging source of medium oscillation pulses, namely controlled valve, at borehole bottom; closing drilling string cross-section with the controlled valve and generating pressure pulses in drilling mud, which is the medium in which oscillations are propagated, wherein two similar pressure sensors arranged at borehole head and spaced apart for not less than 10-20 m along pipeline axis are used as medium oscillation pulse receivers; measuring time of pressure pulse propagation to each pressure sensor and calculating borehole depth from mathematic equation with taking into consideration time of pressure pulse propagation from controlled valve to each pressure sensor, distance between pressure sensors, distance from controlled valve to drilling bit and distance from the first pressure sensor to rotor table.

EFFECT: increased accuracy of borehole depth determination.