Seismic method for determining the position of the bit on a drill stem in a deep borehole

摘要

A method for determining the precise position of the drill bit on the bottom of a long drill string in a deep borehole in the earth during a drilling operation, with a minimum of effort and interruption of the drilling process. It provides placing a plurality of geophones in an array on the surface of the earth above the expected position of the drill bit. A frangible object is inserted into the drill pipe near the surface whereby the mud stream will carry it down through the pipe to the bit where it will close off the mud flow through the bit. The mud pressure above the object will increase and when it reaches a high enough value the object will shatter and there will be a sudden flow of mud through the openings of the bit in the form of a shock wave, which will generate a seismic wave in the earth at the location of the bit. The expanding seismic wave will be detected by the geophones at the surface from which the times of arrival at the various geophones can be determined. The time of initiation of the shock wave can be determined from which the travel times of the seismic wave can be determined and, therefore, the position of the bit with respect to the geophones can be determined.