PROCEDE ET DISPOSITIF POUR MESURER L'ALLURE DES ROCHES A FORER ET POUR REGLER LES PARAMETRES IMPOSES A L'OUTIL DE FORAGE

摘要

1,253,717. Borehole logging. SOC. NATIONALE DES PETROLES D'AQUITAINE. 20 March, 1969 [22 March, 1968], No. 14752/69. Heading H4D. [Also in Division G1] The mechanical properties of rock are measured during a drilling operation by measuring the vibrations of the upper part of the drilling assembly. The vibrations are sensed by a strain gauge bridge circuit responsive to stresses at the top of the drilling assembly and by pick-ups responsive to the longitudinal or torsional acceleration of the top of the drilling assembly. Band pass filters 7, 8 pass components of the stress signal 5 and acceleration signal 6 at the frequency equal to the rotational speed of the drill multiplied by the number of operational elements on the tool. The acceleration signal passes through amplifier 11 and integrator 11a and is added to the stress signal in adding unit 12. The composite signal is amplified at 14, phase-shifted at 16, and supplied to one input each of a differential amplifier 18 and a phase comparator 28. Generator 4 generates an alternating voltage of amplitude proportional to the frequency, which is fed through adjustable gain amplifier 23, adjustable phaseshifter 30 and delay line 32 to be compared in amplitude and phase at 18, 28 respectively with the composite signal. The outputs of differential amplifier 18, integrated at 20, and of phase comparator 28 are used to control the settings of 23, 30 which settings at balance are evaluated at 37 and recorded at 38 as a function of drill depth. The drilling may be controlled in dependance on the rock characteristics, the rotational speed of the drill being varied to find the speed which gives the maximum vibration amplitude and the speed being maintained at the value to give this maximum amplitude.