Abstract: A method for determining a shear slowness of a subterranean formation includes receiving waveforms data acquired by receivers in an acoustic measurement tool in response to energy emitted by at least one dipole source. The waveforms are processed to extract a formation flexural acoustic mode and a tool flexural acoustic mode. The processing includes transforming the time domain waveforms to frequency domain waveforms, processing the frequency domain waveforms with a Capon algorithm to compute a two-dimensional spectrum over a chosen range of group slowness and phase slowness values; and processing the two-dimensional spectrum to extract the multi-mode slowness dispersion.

Abstract: Methods are provided for estimating a quality of cement in the annuli of a multi-string wellbore. Wideband acoustic energy signals are generated and detected in the wellbore and are processed to obtain indications of wideband casing-formation phase slowness dispersions in the wellbore. The indications are compared to reference wideband model casing-formation phase slowness dispersions in order to estimate status of cement or lack of cement in the annuli at that location based on the results of the comparison.

Abstract: Methods are provided for estimating a quality of cement in the annuli of a multi-string wellbore. Wideband acoustic energy signals are generated and detected in the wellbore and are processed to obtain indications of wideband casing-formation phase slowness dispersions in the wellbore. The indications are compared to reference wideband model casing-formation phase slowness dispersions in order to estimate status of cement or lack of cement in the annuli at that location based on the results of the comparison.

Abstract: Methods are disclosed for detecting fluid in at least one annulus around at least one casing installed in a borehole traversing a formation utilizing a sonic tool. The sonic tool is activated in the borehole and the received sonic waveforms are processed to obtain a dispersion plot. A reference dispersion plot is generated using a model of the borehole where the casing is well-bonded by cement. The obtained and reference dispersion plots are compared. An indication of fluid and in some cases, the specific radial location thereof is obtained based on the signature of the obtained plot as opposed to the reference plot. The methods are effective in doubly-cased boreholes using monopole and/or dipole sources.

Abstract: A method for torsional wave logging in a borehole of a subterranean formation. The method includes obtaining a torsional wave measurement of the borehole, wherein the torsional wave measurement represents characteristics of a torsional wave propagating within a cylindrical layered structure associated with the borehole, wherein the cylindrical layered structure comprises the subterranean formation and a completion of the borehole, analyzing, by a computer processor, the torsional wave measurement to generate a quality measure of the completion, and displaying the quality measure of the completion.

Abstract: A computer-implemented method is provided for determining properties of a formation traversed by a well or wellbore. A formation model describing formation properties at an interval-of-interest within the well or wellbore is derived from measured sonic data, resistivity data, and density data for the interval-of-interest. The formation model is used as input to a plurality of petrophysical transforms and corresponding tool response simulators that derive simulated sonic data, resistivity data, and density data for the interval-of-interest. The measured sonic data, resistivity data, and density data for the interval-of-interest and the simulated sonic data, resistivity data, and density data for the interval-of-interest are used by an inversion process to refine the formation model and determine properties of the formation at the interval-of-interest. In embodiments, properties of the formation may be radial profiles for porosity, water saturation, gas or oil saturation, or pore aspect ratio.

Abstract: Oscillators that use resonator elements formed from langasite or one of its isomorphs are described herein. The resonator elements include crystal orientations that are stress and/or temperature compensated. The resonators vibrate at an oscillating frequency in a thickness-shear mode of vibration. The oscillating frequency can be used to derive temperature, derive pressure, and/or for frequency control applications.

Abstract: A method includes applying acoustic waves to the formation and detecting acoustic waves to acquire acoustic data. The method further includes determining (i) at least one of elastic constant C13 and elastic constant C23, (ii) elastic constant C33, (iii) at least one of elastic constant C44 and elastic constant C55, and (iv) elastic constant C66 using the acquired acoustic data. Elastic constant C11 is determined using elastic constant C33, at least one of elastic constant C44 and elastic constant C55, elastic constant C66, and a relationship between Thomsen parameter gamma and Thomsen parameter epsilon.

Abstract: Apparatus and method for characterizing a barrier installed in a borehole traversing a formation including locating an acoustic tool with a receiver and a transmitter at a location in the borehole, activating the acoustic tool to form acoustic waveforms, wherein the receiver records the acoustic waveforms, and processing the waveforms to identify barrier parameters as a function of azimuth and depth along the borehole, wherein the waveforms comprise at least two of sonic signals, ultrasonic pulse-echo signals, and ultrasonic pitch-catch signals.

Abstract: Maximum and minimum horizontal stresses, and horizontal to overburden stress ratio, are estimated using radial profiles of shear moduli. Inversion enables estimation of maximum and minimum horizontal stresses using radial profiles of three shear moduli associated with an orthogonal set of axes defined by the three principal stress directions. Differences in the far-field shear moduli are inverted together with two difference equations obtained from the radial profiles of the dipole shear moduli C44 and C55, and borehole stresses in the near-wellbore region. The horizontal to overburden stress ratio is estimated using differences in the compressional, dipole shear, and Stoneley shear slownesses at two depths in the same lithology interval where the formation exhibits azimuthal isotropy in cross-dipole dispersions, implying that horizontal stresses are nearly the same at all azimuths.

Abstract: A technique facilitates determination of fracture attributes through the recording and analyzing of borehole sonic data before and after a fracturing operation. The technique comprises generating broadband acoustic waves at an array of receivers based on output from a plurality of acoustic sources. The waveforms of the broadband acoustic waves are recorded and processed to estimate sonic signatures. The sonic signatures are then used to determine fracture attributes. In some applications, the data may be used to determine whether the fractures in the formation are filled with fluid or soft sediments. Information on the fracture attributes is output to a suitable system, e.g. a computer display.

Abstract: A method for determining properties of a formation traversed by a well or wellbore employs measured sonic data, resistivity data, and density data for an interval-of-interest within the well or wellbore. A formation model that describe properties of the formation at the interval-of-interest is derived from the measured sonic data, resistivity data, and density data for the interval-of-interest. The formation model is used to derive simulated sonic data, resistivity data, and density data for the interval-of-interest. The measured sonic data, resistivity data, and density data for the interval-of-interest and the simulated sonic data, resistivity data, and density data for the interval-of-interest are used to refine the formation model and determine properties of the formation at the interval-of-interest.

Abstract: A technique includes receiving data representing time domain waveforms acquired by receivers of a drilling string-disposed acoustic measurement tool in response to energy emitted by at least one dipole source of the tool. The technique includes processing the data to determine slowness values associated with a plurality of acoustic modes, including a formation flexural acoustic mode and a tool flexural acoustic mode. The technique includes identifying slowness-frequency pairs from the slowness values and determining a shear slowness based at least in part on the identified slowness-frequency pairs.

Abstract: A method for torsional wave logging in a borehole of a subterranean formation. The method includes obtaining a torsional wave measurement of the borehole, wherein the torsional wave measurement represents characteristics of a torsional wave propagating within a cylindrical layered structure associated with the borehole, wherein the cylindrical layered structure comprises the subterranean formation and a completion of the borehole, analyzing, by a computer processor, the torsional wave measurement to generate a quality measure of the completion, and displaying the quality measure of the completion.

Abstract: Cased-hole radial profiling of shear parameters from sonic measurements is disclosed.

Abstract: Maximum and minimum horizontal stresses are estimated using radial profiles of shear moduli for a deviated borehole. Inversion enables estimation of maximum and minimum horizontal stresses using radial profiles of three shear moduli associated with an orthogonal set of axis defined by the deviated borehole azimuth from the North and the deviation of the longitudinal axis of the borehole from the vertical.

Abstract: A method and apparatus for assessing induced fractures in a subterranean formation including acquiring sonic data before and after a hydraulic fracturing operation, calculating a shear modulus in the borehole cross-sectional plane from Stoneley data, and calculating two shear moduli in two borehole orthogonal axial planes from cross dipole data. A method and apparatus for assessing induced fractures in a subterranean formation including collecting sonic data before and after fracturing the formation, calculating a far-field shear modulus in the borehole cross-sectional plane and a far-field shear moduli in the two orthogonal borehole axial planes, inferring the open or closed status of a fracture, and estimating a radial width or height or both of a vertical fracture.

Abstract: A method includes applying acoustic waves to the formation and detecting acoustic waves to acquire acoustic data. The method further includes determining (i) at least one of elastic constant C13 and elastic constant C23, (ii) elastic constant C33, (iii) at least one of elastic constant C44 and elastic constant C55, and (iv) elastic constant C66 using the acquired acoustic data. Elastic constant C11 is determined using elastic constant C33, at least one of elastic constant C44 and elastic constant C55, elastic constant C66, and a relationship between Thomsen parameter gamma and Thomsen parameter epsilon.

Abstract: A method for torsional wave logging in a borehole of a subterranean formation. The method includes obtaining a torsional wave measurement of the borehole, wherein the torsional wave measurement represents characteristics of a torsional wave propagating within a cylindrical layered structure associated with the borehole, wherein the cylindrical layered structure comprises the subterranean formation and a completion of the borehole, analyzing, by a computer processor, the torsional wave measurement to generate a quality measure of the completion, and displaying the quality measure of the completion.

Abstract: Systems and methods for the estimating a plurality of anisotropic elastic constants (Cij) using borehole dispersions and refracted compressional headwave velocity at a single logging depth in a vertical, deviated, or horizontal wellbore in a transversely-isotropic with a vertical axis of symmetry (“TIV”) formation. The estimated elastic constants can then be used to calculate near-wellbore stress distributions in the wellbore, which aids in an optimal completion design, such as for shale-gas production in the presence of shale heterogeneity.