Abstract: A method and system is described for estimating stress characteristics from seismic data. The method includes receiving seismic data acquired over a region, receiving properties of rock at a location within the region, and estimating one or more stress characteristics for a sub-region by combining the seismic data and the rock properties using a relationship between the stress characteristics in the sub-region and elastic stiffness and/or sonic velocity in the sub-region. The relationship is based on a non-linear elasticity theory.

Abstract: A method for determining properties of a transverse isotropic region of earth formations traversed by a wellbore having substantially vertical and deviated sections therethrough, including measuring sonic velocity properties in formations surrounding the substantially vertical section of the wellbore; measuring sonic velocity properties in formations surrounding the deviated section of the wellbore; and determining, from the measured velocities, all of the transverse isotropic elastic constants of the region.

Abstract: A method for determining properties of a transverse isotropic region of earth formations traversed by a wellbore having substantially vertical and deviated sections therethrough, including measuring sonic velocity properties in formations surrounding the substantially vertical section of the wellbore; measuring sonic velocity properties in formations surrounding the deviated section of the wellbore; and determining, from the measured velocities, all of the transverse isotropic elastic constants of the region.

Abstract: A method for determining properties of an earth formation surrounding an earth borehole that involves: providing a logging device moveable through the borehole; transmitting sonic energy into the formation; receiving sonic energy that has traveled through the formation; producing signals representative of the received sonic energy; determining whether the formation is anisotropic; determining whether the formation is inhomogeneous; and outputting a characterization of the formation as one of the following types: isotropic/homogeneous, anisotropic/homogeneous, isotropic/inhomogeneous, and anisotropic/inhomogeneous.

Abstract: A method for determining a radial profile of sonic shear velocity of formations surrounding a fluid-containing borehole, including: suspending a logging device in the borehole; transmitting sonic energy from the logging device to establish flexural waves in the formation; receiving sonic energy from the flexural waves and producing, from the received sonic energy, measurement signals at a number of frequencies; determining, at each frequency, the flexural wave velocity in the formation; deriving sonic compressional and shear velocities of the substantially undisturbed formation; deriving sonic compressional velocity of the borehole fluid; and determining the radial profile of sonic shear velocity from the derived compressional and shear velocities of the substantially undisturbed formation, the derived compressional velocity of the borehole fluid, and the flexural wave velocities.

Abstract: A method and system is described for estimating stress characteristics from seismic data. The method includes receiving seismic data acquired over a region, receiving properties of rock at a location within the region, and estimating one or more stress characteristics for a sub-region by combining the seismic data and the rock properties using a relationship between the stress characteristics in the sub-region and elastic stiffness and/or sonic velocity in the sub-region. The relationship is based on a non-linear elasticity theory.

Abstract: A method for determining properties of an earth formation surrounding an earth borehole that involves: providing a logging device moveable through the borehole; transmitting sonic energy into the formation; receiving sonic energy that has traveled through the formation; producing signals representative of the received sonic energy; determining whether the formation is anisotropic; determining whether the formation is inhomogeneous; and outputting a characterization of the formation as one of the following types: isotropic/homogeneous, anisotropic/homogeneous, isotropic/inhomogeneous, and anisotropic/inhomogeneous.

Abstract: A method for determining a radial profile of sonic shear velocity of formations surrounding a fluid-containing borehole, including: suspending a logging device in the borehole; transmitting sonic energy from the logging device to establish flexural waves in the formation; receiving sonic energy from the flexural waves and producing, from the received sonic energy, measurement signals at a number of frequencies; determining, at each frequency, the flexural wave velocity in the formation; deriving sonic compressional and shear velocities of the substantially undisturbed formation; deriving sonic compressional velocity of the borehole fluid; and determining the radial profile of sonic shear velocity from the derived compressional and shear velocities of the substantially undisturbed formation, the derived compressional velocity of the borehole fluid, and the flexural wave velocities.

Abstract: A method for determining unknown stress parameters in earth formation measures velocities in four sonic transmissions modes (compression, fast shear, slow shear and Stoneley) at a series of depths. Relationships between measured velocities and other measured values, two independent linear constants, and three nonlinear constants associated with equations of motion for pre-stressed isotropic materials are expressed in a set of four or five velocity difference equations derived from non-linear continuum mechanics. The velocity difference equations are solved using inversion for useful stress parameters, including maximum horizontal stress, minimum horizontal stress, pore pressure, and change in pore pressure over time.

Abstract: A dual-mode thickness-shear quartz pressure transducer includes a unitary piezoelectric crystal resonator and cylindrical housing structure wherein the resonator is located on a median radial plane of the housing and the exterior of the housing is provided with a pair of parallel flat surfaces which are located at an angle relative to the X" axis of the resonator. According to the presently preferred embodiment, the transducer is made from an SC-cut or a WAD-cut solid quartz crystal cylinder which is ultrasonically milled to form a plano-convex or bi-convex resonator disk in the medial radial plane of a hollow cylinder and the pair of exterior flats. The wall thickness of the cylinder is altered at the location of the flats such that stresses at the center of the resonator disk are anisotropic.

Abstract: A method of estimating formation in-situ stress magnitude and nonlinear constants of an earth formation traversed by a borehole includes analyzing the flexural wave dispersions for dipole sources aligned parallel and perpendicular to the maximum far-field compressive stress direction together with the Stoneley wave dispersion derived from a monopole source. In the presence of formation and borehole stresses above and beyond those in an assumed isotropic reference state, the borehole flexural and Stoneley wave velocity dispersions are also functions of the formation stresses and nonlinear constants. A multi-frequency inversion of the flexural or Stoneley wave velocity dispersions over a selected frequency band is performed to determine the uniaxial stress magnitude S and the quantities ##EQU1## where c.sub.111, c.sub.112, and c.sub.123 are the formation non-linear constants.

Abstract: A method of investigating a formation traversed by a borehole includes, measuring at a plurality of different static borehole pressures the acoustic Stoneley and/or flexural wave velocities of waves propagating through the borehole and formation, and generating an indication of the nonlinearity of the formation by processing the velocity measurements. The velocity measurements are processed either by determining a fractional change in the measured acoustic velocity and dividing that fractional change by the change in borehole pressure to provide frequency dependent acoustoelastic coefficients, or by determining the fractional change in the measured acoustic velocity, and subtracting from the fractional change a component generated by the borehole fluid and a component due to linear aspects of the formation to provide a nonlinear formation component. By processing the velocity measurements at a plurality of frequencies, the nonlinear formation components are used to find nonlinear parameters of the formations.

Abstract: Low and high frequency flexural waves or their equivalents are generated with dipole or other source transducers. From measurements made at receiving transducers which are oriented at two orthogonal directions in a horizontal plane normal to the borehole axis, and via known processing techniques, the received signals are transformed into arrivals as a function of frequency such that the principal polarization directions and the magnitudes of the maximum and minimum wave velocities at those directions are determined at different frequencies. If the maximum velocity of the relatively low frequency flexural waves are in a first principal polarization direction, and the maximum velocity of the relatively high frequency flexural waves are in a second principal polarization direction which is substantially normal to the first principal direction, uniaxial stress in the formation is attributed to stress induced azimuthal anisotropy as opposed to an instrinsic anistropy in the formation.

Abstract: Disclosed is a rotated Y-cut, quartz SAW device having a propagation direction gamma and an angular orientation theta selected both for stress compensation and temperature compensation. In a particular embodiment gamma is 46.9.degree. and theta is 41.8.degree..

Abstract: Disclosed is an externally loaded pressure sensor using a pair of SAW devices formed on the wall of an interior cavity. The difference frequency of these devices is used as a temperature-compensated measure of hydrostatic pressure on the sensor exterior. The termal response time of the sensor is shortened by matching to each other the sensor wall thicknesses adjacent the two SAW devices, e.g., by making these wall thicknesses approximately the same by means of forming an external flat on the sensor body.

Abstract: Disclosed is an externally loaded pressure sensor using a pair of SAW devices formed on the wall of an interior cavity. The difference frequency of these devices is used as a temperature-compensated measure of hydrostatic pressure on the sensor exterior. The cavity wall immediately adjacent the long sides of at least one of the SAW devices is rounded, to improve pressure sensitivity without unacceptable increase in stresses or other adverse effects.

Abstract: Pressure sensing diaphragms comprise a cylindrical or spherical crystalline member in which an internal cylindrical or spherical chamber is provided. In the internally loaded embodiments, a fluid is introduced into the chamber and the pressure exerted by the fluid causes generally tensile stress in the region of the diaphragm generally about the chamber. In the externally loaded embodiments, the diaphragm is immersed within the fluid and the pressure exerted by the fluid causes generally compressive stress in the region of the diaphragm generally about the chamber. For each of the embodiments, the stresses arising cause certain mechanical and electrical properties of the crystalline material to change. The change in these properties is detected by observing the frequency behavior of one or more oscillators whose frequencies of operation are controlled by respective surface acoustic wave devices provided in the regions of elastic deformation.

Abstract: Pressure sensing diaphragms comprise a cylindrical or spherical crystalline member in which an internal cylindrical or spherical chamber is provided. In the internally loaded embodiments, a fluid is introduced into the chamber and the pressure exerted by the fluid causes generally tensile stress in the region of the diaphragm generally about the chamber. In the externally loaded embodiments, the diaphragm is immersed within the fluid and the pressure exerted by the fluid causes generally compressive stress in the region of the diaphragm generally about the chamber. For each of the embodiments, the stresses arising cause certain mechanical and electrical properties of the crystalline material to change. The change in these properties is detected by observing the frequency behavior of one or more oscillators whose frequencies of operation are controlled by respective surface acoustic wave devices provided in the regions of elastic deformation.

Abstract: Pressure sensing diaphragms comprise a cylindrical or spherical crystalline member in which an internal cylindrical or spherical chamber is provided. In the internally loaded embodiments, a fluid is introduced into the chamber and the pressure exerted by the fluid causes generally tensile stress in the region of the diaphragm generally about the chamber. In the externally loaded embodiments, the diaphragm is immersed within the fluid and the pressure exerted by the fluid causes generally compressive stress in the region of the diaphragm generally about the chamber. For each of the embodiments, the stresses arising cause certain mechanical and electrical properties of the crystalline material to change. The change in these properties is detected by observing the frequency behavior of one or more oscillators whose frequencies of operation are controlled by respective surface acoustic wave devices provided in the regions of elastic deformation.

Abstract: Pressure sensing diaphragms comprise a cylindrical or spherical crystalline member in which an internal cylindrical or spherical chamber is provided. In the internally loaded embodiments, a fluid is introduced into the chamber and the pressure exerted by the fluid causes generally tensile stress in the region of the diaphragm generally about the chamber. In the externally loaded embodiments, the diaphragm is immersed within the fluid and the pressure exerted by the fluid causes generally compressive stress in the region of the diaphragm generally about the chamber. For each of the embodiments, the stresses arising cause certain mechanical and electrical properties of the crystalline material to change. The change in these properties is detected by observing the frequency behavior of one or more oscillators whose frequencies of operation are controlled by respective surface acoustic wave devices provided in the regions of elastic deformation.