Acoustical measuring device for permeability and fracture investigation of rock formations in drilled through mountains

摘要

The acoustical measuring device consists of a measuring probe which is immersed by means of a cable in the bore hole filled with drilling medium and can be moved in the axial direction therein. The measuring probe contains a transmitter which emits pulses. The echo signals are detected by a receiver fitted in the measuring probe. To detect the geophysically particularly important casing waves, which are received as strong useful signals undisturbed by transient and decay processes, the effective distance between transmitter and receiver in the measuring probe is smaller than half the wavelength of the signal transmitted in the drilling medium. This involves a reflection arrangement of essentially axial oscillators which are broad-band but prefer the lower acoustical frequency range. The measuring time of the sonograms received (microseismograms) is up to about one second. …IMAGE…