METHOD AND SYSTEM FOR SONIC WELL LOGGING

摘要

METHOD AND APPARATUS FOR ACOUSTIC LOGGING OF A BOREHOLE A method and apparatus are described for preferentially exciting for extracting late arrivals at low frequencies in an acoustic investigation of a borehole. The late arrival may be the Stoneley wave whose amplitude is derived by measuring the energy in a predetermined frequency band of a waveform produced with a low frequency transmitter-receiver system. The transmitter produces a highly damped acoustic pulse whose frequency spectrum is selected to preferentially excite a late arrival such as the Stoneley wave and/or tube wave with wavelengths which are significantly greater than the diameter of the borehole while preserving measurable earlier arrivals at higher frequencies. A receiver system is used which provides a generally flat frequency response including low frequencies to produce waveforms of both the earlier arrivals at high frequencies and late arrivals at low frequencies with sufficient extractable amplitudes throughout a wide range of borehole and formation conditions. A method and apparatus are described for measuring inelastic behavior of the formation as well as elastic parameters such as the shear modulus of the material comprising the circumference of the borehole wall by investigating frequency bands in the spectrum of a late arrival such as the Stoneley wave. A display and method for generating the display are described for the investigations of the late arrival.