Abstract: A controller includes: a pulse-width modulation (PWM) circuit; a control loop; and a reference voltage controller. The control loop has: a feedback input adapted to be coupled to an output voltage of a power stage; a control loop output coupled to a PWM control input; and an operational amplifier with a first feedback input, a first reference input, and an amplifier output, the first feedback input connected to the feedback input, and the amplifier output coupled to the PWM control input. The reference voltage controller has a reference voltage output coupled to the first reference input, the reference voltage controller configured to adjust a reference voltage provided to the reference voltage output responsive to a dynamic error estimate based on error in the operational amplifier.

Abstract: A controller includes: a pulse-width modulation (PWM) circuit; a control loop; and a reference voltage controller. The control loop has: a feedback input adapted to be coupled to an output voltage of a power stage; a control loop output coupled to a PWM control input; and an operational amplifier with a first feedback input, a first reference input, and an amplifier output, the first feedback input connected to the feedback input, and the amplifier output coupled to the PWM control input. The reference voltage controller has a reference voltage output coupled to the first reference input, the reference voltage controller configured to adjust a reference voltage provided to the reference voltage output responsive to a dynamic error estimate based on error in the operational amplifier.

Abstract: Methods are provided for determining properties of an anisotropic formation (including both fast and slow formations) surrounding a borehole. A logging-while-drilling tool is provided that is moveable through the borehole. The logging-while drilling tool has at least one dipole acoustic source spaced from an array of receivers. During movement of the logging-while-drilling tool, the at least one dipole acoustic source is operated to excite a time-varying pressure field in the anisotropic formation surrounding the borehole. The array of receivers is used to measure waveforms arising from the time-varying pressure field in the anisotropic formation surrounding the borehole. The waveforms are processed to determine a parameter value that represents shear directionality of the anisotropic formation surrounding the borehole.

Abstract: A method for estimating all five transversely-isotropic (TI)-elastic constants using borehole sonic data obtained from at least one subterranean borehole in a transversely isotropic formation. In an embodiment, the method includes: solving for a quasi-compressional qP-wave velocity VqP using inversion algorithms based on exact solutions of the Kelvin-Christoffel equations for plane wave velocities in arbitrarily anisotropic formations, where the five TI-elastic constants may include C11, C13, C33, C55, and C66.

Abstract: A controller includes: a pulse-width modulation (PWM) circuit; a control loop; and a reference voltage controller. The control loop has: a feedback input adapted to be coupled to an output voltage of a power stage; a control loop output coupled to a PWM control input; and an operational amplifier with a first feedback input, a first reference input, and an amplifier output, the first feedback input connected to the feedback input, and the amplifier output coupled to the PWM control input. The reference voltage controller has a reference voltage output coupled to the first reference input, the reference voltage controller configured to adjust a reference voltage provided to the reference voltage output responsive to a dynamic error estimate based on error in the operational amplifier.

Abstract: Methods are provided for determining properties of an anisotropic formation (including both fast and slow formations) surrounding a borehole. A logging-while-drilling tool is provided that is moveable through the borehole. The logging-while drilling tool has at least one dipole acoustic source spaced from an array of receivers. During movement of the logging-while-drilling tool, the at least one dipole acoustic source is operated to excite a time-varying pressure field in the anisotropic formation surrounding the borehole. The array of receivers is used to measure waveforms arising from the time-varying pressure field in the anisotropic formation surrounding the borehole. The waveforms are processed to determine a parameter value that represents shear directionality of the anisotropic formation surrounding the borehole.

Abstract: Methods are provided for determining properties of an anisotropic formation (including both fast and slow formations) surrounding a borehole. A logging-while-drilling tool is provided that is moveable through the borehole. The logging-while drilling tool has at least one dipole acoustic source spaced from an array of receivers. During movement of the logging-while-drilling tool, the at least one dipole acoustic source is operated to excite a time-varying pressure field in the anisotropic formation surrounding the borehole. The array of receivers is used to measure waveforms arising from the time-varying pressure field in the anisotropic formation surrounding the borehole. The waveforms are processed to determine a parameter value that represents shear directionality of the anisotropic formation surrounding the borehole.

Abstract: Methods and systems are provided that identify relatively large anisotropic horizontal stresses in a formation based on (i) azimuthal variations in the compressional and shear slownesses or velocities of the formation measured from ultrasonic data acquired by at least one acoustic logging tool as well as (ii) cross-dipole dispersions of the formation measured from sonic data acquired by the at least one acoustic logging tool. In addition, the azimuthal variations in the compressional and shear slownesses or velocities of the formation and dipole flexural dispersions of the formation can be jointly inverted to obtain the elastic properties of the rock of the formation in terms of linear and nonlinear constants and the magnitude of maximum horizontal stress of the formation. A workflow for estimating the magnitude of the maximum horizontal stress can employ estimates of certain formation properties, such as overburden stress, magnitude of minimum horizontal stress, and pore pressure.

Abstract: Methods arc provided for using sonic tool data to investigate a multi-string wcllbore. The sonic data is processed to obtain indications of phase slowness dispersions for multiple locations in the wellbore. The dispersions are aggregated. The aggregated dispersions are compared with a plurality of cut-off mode templates to identify the presence of cut-off modes or the lack thereof in the aggregated phase slowness dispersions. Features of the multi-string wellbore are identified based on the presence of the cut-off modes or the lack thereof. In another method, the sonic data is processed to obtain indications as a function of depth of at least one of an energy spectrum, a semblance projection, a slowness dispersion projection, an attenuation dispersion projection, and a wavenumber dispersion projection. The indications are inspected to locate a shift at a particular depth indicat- ing a transition in at least oneannulus of the multi-string wellbore.

Abstract: Methods and systems are provided for determining cement quality in an outer annulus of a multi-string cased wellbore having an inner annulus of mud. Data from a sonic logging tool is processed to obtain a slowness dispersion. The slowness dispersion is compared to a plurality of model slowness dispersions generated for a plurality of different values for cement quality in the outer annulus. The cement quality in the outer annulus is determined based on the comparison.

Abstract: The present disclosure provides methods and systems for analyzing cement integrity in a depth interval of a wellbore having a multiple string casing with an innermost annulus disposed inside at least one outer annulus. The method includes processing ultrasonic data obtained from ultrasonic measurements on the interval of the wellbore to determine properties of the innermost annulus. The method also includes processing sonic data obtained from sonic measurements on the interval of the wellbore to extract features of the sonic data. The features of the sonic data are input to a machine learning processing to determine properties of both the innermost annulus and the least one outer annulus. Additional processing of ultrasonic and sonic data can also be used to determine properties of both the innermost annulus and the least one outer annulus. These properties can be used to analyze cement integrity in the depth interval of the wellbore.

Abstract: Methods utilizing ultrasonic acoustic logging tools are provided for detecting thin formation layers that present markedly higher compliance than that of the surrounding rock in, for example, a laminated tight hydrocarbon-bearing formation. These layers may be interpreted as presenting potential interfacial and planes of weakness that may have bearing on the extent of a hydraulic fracture propagating across them.

Abstract: Methods are provided for identifying a cementation status of a multi-string cased wellbore utilizing sonic tools with monopole and/or dipole transmitters and with an array of sonic receivers axially displaced from the transmitter(s). The sonic tool is used to record waveforms. The waveforms are then processed to generate slowness and/or attenuation dispersions. The slowness and/or attenuation dispersions are projected onto a slowness and/or attenuation axis, and the results are compared to a data set of projected slowness and/or attenuation dispersions representing a plurality of different multi-string cased wellbore cement status scenarios in order to select the scenario most closely associated with the results. The presence or lack of eccentering of a casing is similarly obtained where the data set includes projected dispersions representing properly centered and ec-centered casings.

Abstract: Methods and devices for data migration may include initially processing requests from a plurality of geographic regions for a cloud service using a global back-end service with a global storage account storing data. The methods and devices may include establishing a region back-end service with a region storage account in at least one geographic region of the plurality of geographic regions to support the cloud service for users in the at least one geographic region, wherein the region back-end service includes a region RTable. The methods and devices may include receiving, by the region back-end service, user requests for the cloud service from one or more users in the at least one geographic region and accessing, via the region RTable, one or more rows of data associated with the at least one geographic region from the global storage account in response to the user requests.

Abstract: A method for estimating all five transversely-isotropic (TI)-elastic constants using borehole sonic data obtained from at least one subterranean borehole in a transversely isotropic formation. In an embodiment, the method includes: solving for a quasi-compressional qP-wave velocity VqP using inversion algorithms based on exact solutions of the Kelvin-Christoffel equations for plane wave velocities in arbitrarily anisotropic formations, where the five TI-elastic constants may include C11, C13, C33, C55, and C66.

Abstract: Methods and systems are provided that identify relatively large anisotropic horizontal stresses in a formation based on (i) azimuthal variations in the compressional and shear slownesses or velocities of the formation measured from ultrasonic data acquired by at least one acoustic logging tool as well as (ii) cross-dipole dispersions of the formation measured from sonic data acquired by the at least one acoustic logging tool. In addition, the azimuthal variations in the compressional and shear slownesses or velocities of the formation and dipole flexural dispersions of the formation can be jointly inverted to obtain the elastic properties of the rock of the formation in terms of linear and nonlinear constants and the magnitude of maximum horizontal stress of the formation. A workflow for estimating the magnitude of the maximum horizontal stress can employ estimates of certain formation properties, such as overburden stress, magnitude of minimum horizontal stress, and pore pressure.

Abstract: Methods are provided for determining properties of an anisotropic formation (including both fast and slow formations) surrounding a borehole. A logging-while-drilling tool is provided that is moveable through the borehole. The logging-while drilling tool has at least one dipole acoustic source spaced from an array of receivers. During movement of the logging-while-drilling tool, the at least one dipole acoustic source is operated to excite a time-varying pressure field in the anisotropic formation surrounding the borehole. The array of receivers is used to measure waveforms arising from the time-varying pressure field in the anisotropic formation surrounding the borehole. The waveforms are processed to determine a parameter value that represents shear directionality of the anisotropic formation surrounding the borehole.

Abstract: Methods arc provided for using sonic tool data to investigate a multi-string wcllbore. The sonic data is processed to obtain indications of phase slowness dispersions for multiple locations in the wellbore. The dispersions are aggregated. The aggregated dispersions are compared with a plurality of cut-off mode templates to identify the presence of cut-off modes or the lack thereof in the aggregated phase slowness dispersions. Features of the multi-string wellbore are identified based on the presence of the cut-off modes or the lack thereof. In another method, the sonic data is processed to obtain indications as a function of depth of at least one of an energy spectrum, a semblance projection, a slowness dispersion projection, an attenuation dispersion projection, and a wavenumber dispersion projection. The indications are inspected to locate a shift at a particular depth indicat- ing a transition in at least oneannulus of the multi-string wellbore.

Abstract: Methods utilizing ultrasonic acoustic logging tools are provided for detecting thin formation layers that present markedly higher compliance than that of the surrounding rock in, for example, a laminated tight hydrocarbon-bearing formation. These layers may be interpreted as presenting potential interfacial and planes of weakness that may have bearing on the extent of a hydraulic fracture propagating across them.

Abstract: Methods are provided for identifying a cementation status of a multi-string cased wellbore utilizing sonic tools with monopole and/or dipole transmitters and with an array of sonic receivers axially displaced from the transmitter(s). The sonic tool is used to record waveforms. The waveforms are then processed to generate slowness and/or attenuation dispersions. The slowness and/or attenuation dispersions are projected onto a slowness and/or attenuation axis, and the results are compared to a data set of projected slowness and/or attenuation dispersions representing a plurality of different multi-string cased wellbore cement status scenarios in order to select the scenario most closely associated with the results. The presence or lack of eccentering of a casing is similarly obtained where the data set includes projected dispersions representing properly centered and ec-centered casings.