Abstract: An acoustic well logging method and apparatus utilizes a rare earth acoustic transducer to provide low frequency acoustic energy within the borehole, and characteristics of a subsurface geological formation, such as the formation dip, may be obtained by measuring the amplitude of the shear wave and combining that amplitude with known data comprising a graph of shear wave amplitude plotted against incidence angle at known frequencies.

Abstract: An acoustic well logging method and apparatus utilizes a rare earth acoustic transducer to provide low frequency acoustic energy within the borehole, and characteristics of a subsurface geological formation may be obtained, such as the formation permeability by measuring values of the attenuation of the Stoneley waves produced by the rare earth acoustic transducer.

Abstract: Using waveforms or travel time acquired by multitransmitter and/or borehole sonic tools, acoustic velocity (or slowness) is computed for compressional, shear, and Stoneley waves using direct phase determination (DPD), the slowness time coherence (STC) method, and multiple shot processing (MSP). There is a nonzero difference between transmitter and receiver delta-t's (slownesses) when the sonic tool is in the vicinity of a borehole feature, such as a fracture or a borehole enlargement. The amount of the difference, T/R delta-t, for compressional, shear and Stoneley waves depends on the size and nature of the fracture(s). It is possible to determine the height, width, and dip angle of the fracture when the T/R delta-t's are used in conjunction with other model data. It is also possible to distinguish between borehole enlargements and fractures with the method of this invention.

Abstract: Methods and apparatus are described for estimating shear wave slowness of formations traversed by a borehole from guided wave acoustic log data. Acoustic energy is generated at a point in the borehole and received at at least four receiver stations spaced one from the other and from the generating point. Full wave forms of the received signals are produced and windowed to identify guided wavelets. Fourier transforms of the guided wavelets are obtained and from these determined the phase velocity and frequency of the guided wavelet. Values of formation density, drilling fluid density, drilling fluid slowness and borehole diameter are measured and a value of Poissons ratio may be estimated. A multi-dimensional matrix is established comprised of predetermined ranges of assumed values of frequency, Poissons ratio, drilling fluid slowness, drilling fluid density, formation density, phase velocity and borehole diameter.