Abstract: Array quadrupole data obtained in a LWD environment are processed to determine the shear velocity of an earth formation taking into account dispersion effects caused by the logging tool. When this processing is done in an azimuthally anisotropic formation, the shear velocity that is obtained is the slow shear velocity. When 4C (cross-dipole) data are also obtained, then both the fast and slow shear velocities of an azimuthally anisotropic formation can be obtained.

Abstract: Measurements made by a cross-dipole acoustic logging tool in a borehole are processed to determine the principal directions of azimuthal anisotropy of a subsurface formation. Measurements indicative of azimuthal resistivity variations are also made with a multicomponent induction logging tool. These electrical measurements are processed using the principal direction determined from acoustic measurements to give an estimate of azimuthal resistivity variations. Based on modeling results, azimuthal resistivity variations are interpreted to estimate a fracture depth in the rock for known fluids therein.

Abstract: The present invention is a method of determining formation horizontal shear wave velocity, formation transverse isotropy and an effective logging tool modulus. The method comprises determining an effective logging tool modulus by modeling the logging tool as a fluid filled cylindrical shell. Measured Stoneley-wave slowness values are acquired for a formation. A horizontal formation shear wave velocity, Vsh, is calculated as a function of the measured Stoneley-wave slowness and an estimated Stoneley-wave slowness wherein the estimated average Stoneley-wave slowness is computed using the effective tool modulus. A difference between the measured Stoneley-wave slowness and the estimated Stoneley-wave slowness is minimized and the horizontal shear-wave velocity value for the minimized difference is output. Transverse isotropy may be then be calculated as a function of the determined Vsh and vertical shear wave velocity, Vsv, determined from standard logging techniques.

Abstract: The logging tool of this invention includes a transmitter conveyed on a drilling collar for exciting a quadrupole signal in a borehole being drilled by a drill bit and a receiver for receiving the signal. The transmitter is operated at a frequency below the cut-off frequency of the quadrupole collar mode. The received signal consists primarily of the formation quadrupole mode which, at low frequencies, has a velocity that approaches the formation shear velocity. The transmitter, in one embodiment, consists of eight equal sectors of a piezoelectric cylinder mounted on the rim of the drilling collar. The value of the cut-off frequency is primarily dependent on the thickness of the drilling collar. Alternatively, the transmitter may be operated to produce both the collar mode and the formation mode and a processor may be used to filter out the collar mode.

Abstract: Array quadrupole data obtained in a LWD environment are processed to determine the shear velocity of an earth formation taking into account dispersion effects caused by the logging tool. When this processing is done in an azimuthally anisotropic formation, the shear velocity that is obtained is the slow shear velocity. When 4C (cross-dipole) data are also obtained, then both the fast and slow shear velocities of an azimuthally anisotropic formation can be obtained.

Abstract: Directional acoustic measurements made in the borehole are used for imaging a near-borehole geological formation structure and determination of its orientation. Four-component cross-dipole data set measured in a deviated borehole in combination with the directionality of the compressional waves in the dipole data give the orientation of bed boundaries crossing the borehole. The low-frequency content (2˜3 kHz) of the data allows for imaging the radial extent of the formation structure up to 15 m, greatly enhancing the penetration depth as compared to that obtained using conventional monopole compressional-wave data. A combination monopole/dipole arrangement of sources and receivers may also be used for imaging of bed boundaries.

Abstract: Measurements made by a cross-dipole acoustic logging tool in a borehole are processed to determine the principal directions of azimuthal anisotropy of a subsurface formation. Measurements indicative of azimuthal resistivity variations are also made with a multicomponent induction logging tool. These electrical measurements are processed using the principal direction determined from acoustic measurements to give an estimate of azimuthal resistivity variations. Based on modeling results, azimuthal resistivity variations are interpreted to estimate a fracture depth in the rock for known fluids therein.

Abstract: The present invention is a method of determining formation horizontal shear wave velocity, formation transverse isotropy and an effective logging tool modulus. The method comprises determining an effective logging tool modulus by modeling the logging tool as a fluid filled cylindrical shell. Measured Stoneley-wave slowness values are acquired for a formation. A horizontal formation shear wave velocity, Vsh, is calculated as a function of the measured Stoneley-wave slowness and an estimated Stoneley-wave slowness wherein the estimated average Stoneley-wave slowness is computed using the effective tool modulus. A difference between the measured Stoneley-wave slowness and the estimated Stoneley-wave slowness is minimized and the horizontal shear-wave velocity value for the minimized difference is output. Transverse isotropy may be then be calculated as a function of the determined Vsh and vertical shear wave velocity, Vsv, determined from standard logging techniques.

Abstract: The logging tool of this invention includes a transmitter conveyed on a drilling collar for exciting a quadrupole signal in a borehole being drilled by a drill bit and a receiver for receiving the signal. The transmitter is operated at a frequency below the cut-off frequency of the quadrupole collar mode. The received signal consists primarily of the formation quadrupole mode which, at low frequencies, has a velocity that approaches the formation shear velocity. The transmitter, in one embodiment, consists of eight equal sectors of a piezoelectric cylinder mounted on the rim of the drilling collar. The value of the cut-off frequency is primarily dependent on the thickness of the drilling collar. Alternatively, the transmitter may be operated to produce both the collar mode and the formation mode and a processor may be used to filter out the collar mode.