Abstract: Methods and related systems are described for measuring acoustic signals in a borehole during a fracturing operation. The system includes a downhole toolstring designed and adapted for deployment in a borehole formed within a subterranean rock formation. A downhole rock fracturing tool opens and propagates a fracture in the subterranean rock formation. Dipole and/or quadrupole acoustic sources transmit acoustic energy into the subterranean rock formation. A receiver array measures acoustic energy traveling through the subterranean rock formation before, during and after the fracture induction. Geophones mounted on extendable arms can be used to measure shear wave acoustic energy travelling in the rock formation. The toolstring can be constructed such that the sources and receivers straddle the fracture zone during the fracturing.

Abstract: Methods and related systems are described for measuring acoustic signals in a borehole during a fracturing operation. The system includes a downhole toolstring designed and adapted for deployment in a borehole formed within a subterranean rock formation. A downhole rock fracturing tool opens and propagates a fracture in the subterranean rock formation. Dipole and/or quadrupole acoustic sources transmit acoustic energy into the subterranean rock formation. A receiver array measures acoustic energy traveling through the subterranean rock formation before, during and after the fracture induction. Geophones mounted on extendable arms can be used to measure shear wave acoustic energy travelling in the rock formation. The toolstring can be constructed such that the sources and receivers straddle the fracture zone during the fracturing.

Abstract: Methods and related apparatus for generating dispersion curves and conducting shear slowness logging are set forth. The methods include backpropagating detected dispersive waveforms in the Fourier domain while accounting for dispersion in an anisotropic and inhomogeneous formation, and stacking the processed waveforms. The stacking may occur in the frequency or time domains. The semblance of the stacked and windowed waveforms is compared against the detected waveforms. In accounting for dispersion during backpropagation, a plurality of parameters which describe dispersion curves are varied over ranges in order to optimize semblance. At each depth of interest, it is then possible to obtain a dispersion curve of greatest semblance. Where both an x-dipole and y-dipole are used to generate the waves, a dispersion curve of greatest semblance for each may be generated. In addition, from the dispersion curves, formation shear slowness(es) may be plotted as a function of formation depth and orientation.

Abstract: Methods and related apparatus for generating dispersion curves and conducting shear slowness logging are set forth. The methods include backpropagating detected dispersive waveforms in the Fourier domain while accounting for dispersion in an anisotropic and inhomogeneous formation, and stacking the processed waveforms. The stacking may occur in the frequency or time domains. The semblance of the stacked and windowed waveforms is compared against the detected waveforms. In accounting for dispersion during backpropagation, a plurality of parameters which describe dispersion curves are varied over ranges in order to optimize semblance. At each depth of interest, it is then possible to obtain a dispersion curve of greatest semblance. Where both an x-dipole and y-dipole are used to generate the waves, a dispersion curve of greatest semblance for each may be generated. In addition, from the dispersion curves, formation shear slowness(es) may be plotted as a function of formation depth and orientation.

Abstract: An acoustic logging tool includes external baffle assemblies forming a waveguide structure at the acoustic source. The logging tool is designed for acoustic logging of earth formation surrounding a borehole. The external baffle assemblies form a waveguide structure that is designed to increase signal to noise ratio in an acoustic logging tool using dipole or other acoustic waves. In a preferred embodiment, the acoustic logging tool includes an elongated transmitter module, and a receiver sonde having a linear array of acoustic receivers. The transmitter module includes first and second cylindrical masses spaced apart along the axis by first and second spacers. The first cylindrical mass defines a first circular facing surface and a first cylindrical outer surface. The second cylindrical mass defines a second circular facing surface and a second cylindrical outer surface.

Abstract: An acoustic logging tool includes external baffle assemblies forming a waveguide structure at the acoustic source. The logging tool is designed for acoustic logging of earth formation surrounding a borehole. The external baffle assemblies form a waveguide structure that is designed to increase signal to noise ratio in an acoustic logging tool using dipole or other acoustic waves. In a preferred embodiment, the acoustic logging tool includes an elongated transmitter module, and a receiver sonde having a linear array of acoustic receivers. The transmitter module includes first and second cylindrical masses spaced apart along the axis by first and second spacers. The first cylindrical mass defines a first circular facing surface and a first cylindrical outer surface. The second cylindrical mass defines a second circular facing surface and a second cylindrical outer surface.