Development of Turbodrill Tachometer

Abstract

A reliable tachometer has been developed for use with turbodrills. The tachometer utilizes a set of partially blanked turbine blades to produce a pressure pulse in the drilling mud flow steam each time the turbodrill rotates one revolution. The pressure pulses are transmitted through the mud in the drill pipe to the surface where they are detected, processed and RPM read out. The frequency of the pulse signals is a direct measure of the turbodrill rotary speed. Drilling motor test stand trials demonstrated the reliability and accuracy of the tachometer. The pulsing blades were then installed on geothermal turbodrills used in drilling the Los Alamos Scientific Laboratory geothermal well EE-2. The tachometer allowed continual monitoring and control of turbodrill speed at LASL and was successfully used to depths in excess of 10,000 feet. The success of the high temperature turbodrills, in EE-2 is attributed in par to the tachometer.