A method by which physical and mechanical characteristics of rocks are measured during drilling, comprises picking up a signal representing the vibrations of a train of rods forming part of drilling gear, selecting the components of the said signal which, after peak-clipping, are in a frequency band which is centered on, and preferably is related to, a characteristic frequency of the tool, establishing from the components thus selected, a value which is representative of the amplitude of the vibrations, and correlating this value with the drilling depth.
The present invention relates to a method for obtaining a recording or log of measurements substantially comparable to the acoustic impedance of the formations crossed through by the borehole. The measurements are obtained from an acceleration detector (11) placed in the drill string (2) between the rock-breaking bit (7) and mechanical uncoupling system (12) set between certain elements of the string. A measurement representative of the acoustic impedance of the drilled formations is obtained by processing the signal by a function of the rotating speed of the drill bit and of the depth.
An apparatus and a method are provided for detecting and measuring vibrations of a selected portion of a drill string in a bore hole. The vibrations are detected by a transducer which produces an electrical signal representative of the vibrations. The signal is applied to a band-pass filter which produces an output signal representative of vibrations occurring at frequencies within the pass band of the filter. The pass band is repetitively stepped through a predetermined frequency range under the control of digital circuitry.
The invention is related to a method of determininng the instantaneous rotation speed of a drill string or a drill bit in a borehole or the lateral shocks applied to the string or bit. The centripetal acceleration of the drill string is measured at at least two opposite ends of a drill string diameter so as to obtain two centripetal acceleration signals ac1 and ac2; the signals ac1 and ac2 are combined and the instantaneous rotation speed or the lateral shocks are derived from said combined signal. The accelerometers must be of the type delivering a signal with a DC component. An important application of the invention is to transform drill string rotation speed dependent data acquired versus time with a constant sampling time increment T.sub.c separating successive data, into compensated data which would be obtained for a substantially constant drill string rotation speed S.sub.c. The compensated data are obtained either by adjusting the constant sampling time interval T.sub.c into a variable sampling time increment T.sub.v, using the measured instantaneous rotation speed S, or by selecting the data which have been acquired during periods of time during which the instantaneous rotation speed of the drill string varied within predetermined limits only.
The relative positioning of two wells is determined by receiving at a subsurface location in one of the wells sound emanating from the second well, and determining the direction of the second well from the first by reference to the direction of approach of the sound.
A drillstem loading and behavior measurement method and system includes spaced apart subs disposed at the upper end of the drillstem and connected to each other and to a power or conventional swivel and having strain gages and accelerometers mounted thereon in such a way as to measure axial loading, axial vibration, torsional loading, torsional vibration and bending modes of the drillstem during operation. Accelerometers are mounted on respective ones of the subs at a distance from each other sufficient to determine vibration waveforms in axial, torsional and bending modes.
