Abstract: A look-ahead logging method includes obtaining an initial resistivity log. The method further includes deriving an initial formation model based on the initial resistivity log. The method further includes estimating deep resistivity measurements from the initial formation model and deriving a reduced-complexity formation model from the estimated deep resistivity measurements. The method further includes collecting actual resistivity measurements and inverting the actual resistivity measurements, using the reduced-complexity formation model, to obtain look-ahead or look-around parameter values. The method further includes displaying the look-ahead or look-around parameter values or storing the look-ahead or look-around parameter values on a non-transient information storage medium.

Abstract: A look-ahead logging method includes obtaining an initial resistivity log. The method further includes deriving an initial formation model based on the initial resistivity log. The method further includes estimating deep resistivity measurements from the initial formation model and deriving a reduced-complexity formation model from the estimated deep resistivity measurements. The method further includes collecting actual resistivity measurements and inverting the actual resistivity measurements, using the reduced-complexity formation model, to obtain look-ahead or look-around parameter values. The method further includes displaying the look-ahead or look-around parameter values or storing the look-ahead or look-around parameter values on a non-transient information storage medium.

Abstract: Apparatus and methods to generate a two-dimensional image of the well can include control of measurements in a well to generate a log of the well and use of such measurements and/or logs with a log of a reference well. The boundary positions of layers of the well can be correlated with corresponding boundary positions from the reference well. Such apparatus and methods or similar apparatus and methods can be implemented in a variety of applications.

Abstract: An example method includes measuring, with a sensor tool, an electromagnetic field generated by an excitation source in order to determine an azimuth angle from the sensor tool to the source. An initial calibration of the sensor tool is performed to generate a library of sensor tool constant coefficients. Each sensor tool coefficient in the library is associated with a different range of azimuth angles. A sensor tool constant coefficient is selected from the library of sensor tool constant coefficients in response to the azimuth angle from the sensor tool to the source. The gradient field component of down hole measurements provided by the sensor tool are then calibrated based on the selected sensor tool constant coefficient.

Abstract: A micro-resistivity caliper, in some embodiments, comprises a cylindrical body; multiple center electrodes, arranged circumferentially about the cylindrical body, to emit current into a borehole and toward a borehole wall; multiple focus electrodes to limit dispersion of the current emitted by the center electrodes, each of the focus electrodes surrounding a different center electrode; multiple return electrodes to receive the current emitted by the center electrodes, each of the return electrodes surrounding a different focus electrode; and one or more processors, coupled to the return electrodes, to determine one or more standoffs between the micro-resistivity caliper and the borehole wall based on the currents received from the multiple return electrodes.

Abstract: A system and method for minimizing the standoff effect on an imaging tool in a borehole are provided. The imaging tool may include a sensor assembly for transmitting current in the direction of the formation to obtain complex measurements having a real part and an imaginary part. The real-part measurement may be sensitive to, or affected by, the resistivity of the formation and the standoff of the imaging tool. The imaginary-part measurement may be affected by only to standoff. A computing device may determine a ratio using the imaginary-part measurement and corresponding to change in standoff at various imaging tool azimuths. The ratio may be applied to the real-part measurement to enhance the resolution of image data corresponding to formations adjacent to the wellbore.

Abstract: Improved algorithm for estimating anisotropic formation resistivity profile using a multi-component induction tool are disclosed. A method for estimating anisotropic formation resistivity profile of a formation comprises obtaining borehole corrected log data and determining at an azimuth angle of the formation. One or more formation bed boundaries are located and initial formation properties are calculated. One of a plurality of inversion windows is sequentially selected and a one-dimensional inversion of each of the sequentially selected one of the plurality of inversion windows is performed.

Abstract: Various embodiments include apparatus and methods to operate a drilling operation relative to formation boundaries. The apparatus and methods can include operating one or more transmitters in a borehole in a formation having a thickness between two boundaries, selecting thickness models based on applying responses from operating the one or more transmitters such that the thickness of the formation is between the two thickness models, and generating a value of a distance to a nearest boundary based on linearization of the thickness models with respect to a long distance investigation parameter and a short distance investigation parameter. Additional apparatus, systems, and methods are disclosed.

Abstract: A method of obtaining position of a downhole tool with respect to a wellbore includes logging well data via the tool over a period of time and measuring a lateral acceleration of the tool over the period of time with one or more accelerometers embedded in the tool. The method further includes performing double integration on an acceleration of the tool over a period of time. The method also includes obtaining a displacement of the tool over the period of time from the double integration. The method also includes fitting the displacement of the tool over the period of time to a best fit curve. The method also includes subtracting the best fit curve from the displacement of the tool over the period of time.

Abstract: Apparatus and methods to generate a two-dimensional image of the well can include control of measurements in a well to generate a log of the well and use of such measurements and/or logs with a log of a reference well. The boundary positions of layers of the well can be correlated with corresponding boundary positions from the reference well. Such apparatus and methods or similar apparatus and methods can be implemented in a variety of applications.

Abstract: A micro-resistivity caliper, in some embodiments, comprises a cylindrical body; multiple center electrodes, arranged circumferentially about the cylindrical body, to emit current into a borehole and toward a borehole wall; multiple focus electrodes to limit dispersion of the current emitted by the center electrodes, each of the focus electrodes surrounding a different center electrode; multiple return electrodes to receive the current emitted by the center electrodes, each of the return electrodes surrounding a different focus electrode; and one or more processors, coupled to the return electrodes, to determine one or more standoffs between the micro-resistivity caliper and the borehole wall based on the currents received from the multiple return electrodes.

Abstract: An example method includes measuring, with a sensor tool, an electromagnetic field generated by an excitation source in order to determine an azimuth angle from the sensor tool to the source. An initial calibration of the sensor tool is performed to generate a library of sensor tool constant coefficients. Each sensor tool coefficient in the library is associated with a different range of azimuth angles. A sensor tool constant coefficient is selected from the library of sensor tool constant coefficients in response to the azimuth angle from the sensor tool to the source. The gradient field component of down hole measurements provided by the sensor tool are then calibrated based on the selected sensor tool constant coefficient.

Abstract: A system and method for minimizing the standoff effect on an imaging tool in a borehole are provided. The imaging tool may include a sensor assembly for transmitting current in the direction of the formation to obtain complex measurements having a real part and an imaginary part. The real-part measurement may be sensitive to, or affected by, the resistivity of the formation and the standoff of the imaging tool. The imaginary-part measurement may be affected by only to standoff. A computing device may determine a ratio using the imaginary-part measurement and corresponding to change in standoff at various imaging tool azimuths. The ratio may be applied to the real-part measurement to enhance the resolution of image data corresponding to formations adjacent to the wellbore.

Abstract: Methods and systems for reducing shoulder effect are disclosed. Some method embodiments include obtaining resistivity logging data corresponding to a resistivity logging tool's position in a formation position; performing an anisotropic single-layer inversion on the resistivity logging data to determine a horizontal resistivity, a vertical resistivity, and a dip angle of the formation at the tool's position; detecting a location of a boundary of the formation and performing a vertical multi-layer inversion based on the resistivity logging data in a window around said location, if a residual error for the anisotropic inversion exceeds a threshold; and displaying a log of at least one inversion parameter from the anisotropic inversion or the vertical inversion based on said residual error.

Abstract: Techniques for processing down hole information including detecting bed boundaries are disclosed. In some embodiments, a bottom hole assembly includes a down hole tool and a processing apparatus. The down hole tool includes at least one antenna pair to determine resistivity data during rotation of the down hole tool. The processing apparatus is attached to the down hole tool and includes a machine-readable medium that stores a formation model database comprising multiple formation models. The processing apparatus further includes a processor that executes program code to receive the resistivity data during down hole operation of the down hole tool, and to solve for at least resistivity formation parameters using a selected one of the formation models and a selected portion of the received resistivity data. The processor further executes program code to update the selected formation model based, at least in part, on the resistivity formation parameters.

Abstract: Systems, methods, and software for detecting boundary locations of multiple subsurface layers are described. In some aspects, the boundaries of multiple subsurface layers in a subterranean region are identified based on measurements associated with multiple different transmitter-receiver spacings. The measurements are generated based on operating multiple transmitters and multiple receivers of a resistivity logging tool at a tool depth in a wellbore in the subterranean region. A first pair of the subsurface boundary locations are determined based on a first measurement associated with a first transmitter-receiver spacing. A second, different pair of the subsurface boundary locations are determined based on a second measurement associated with a second, longer transmitter-receiver spacing. The first pair of subsurface boundary locations reside between the second pair of subsurface boundary locations in the subterranean region.

Abstract: An example method for fracture identification and characterization may include positioning a magnetic dipole transmitter and a magnetic dipole receiver within a borehole in a subterranean formation. At least one of the magnetic dipole transmitter and the magnetic dipole receiver may be tiled with respect to an axis of the borehole. The magnetic dipole transmitter may generate a time-varying electromagnetic (EM) signal. The magnetic dipole receiver may measure a response of the formation to the time-varying EM signal; the response may include at least two depths of a formation and at least two azimuthal orientations of the formation with respect to the axis of the borehole. An image of the formation may be generated based, at least in part, on the response, and at least one fracture characteristic may be determined based, at least in part, on the first image and a synthetic fracture image.

Abstract: Techniques for processing down hole information including detecting bed boundaries are disclosed. In some embodiments, a bottom hole assembly includes a down hole tool and a processing apparatus. The down hole tool includes at least one antenna pair to determine resistivity data during rotation of the down hole tool. The processing apparatus is attached to the down hole tool and includes a machine-readable medium that stores a formation model database comprising multiple formation models. The processing apparatus further includes a processor that executes program code to receive the resistivity data during down hole operation of the down hole tool, and to solve for at least resistivity formation parameters using a selected one of the formation models and a selected portion of the received resistivity data. The processor further executes program code to update the selected formation model based, at least in part, on the resistivity formation parameters.

Abstract: In some embodiments, an apparatus and a system, as well as a method and an article, may operate to acquire input data to determine properties of a formation, using a combination of down hole transmitters and receivers, to select a portion of the input data using a formation model chosen from a plurality of down hole tool response models in a formation model database, based on a valid sensitive range for the bed boundary distance and a greatest signal-to-noise ratio (SNR), and to solve for at least resistivity formation parameters in the properties using the chosen formation model and the selected portion of the input data. The database may be updated with boundary distance and the resistivity formation parameters. Additional apparatus, systems, and methods are disclosed.

Abstract: Various embodiments include apparatus and methods of operation with respect to well logging. Apparatus and methods include a tool having an arrangement of transmitters and receivers that are operated at different positions downhole and a processing unit to process collected signals such that the arrangement of transmitters and receivers provides measurements that mimic operation of a different arrangement of transmitters and receivers. Additional apparatus, systems, and methods are disclosed.