Abstract: An apparatus for estimating a property of an earth formation penetrated by a borehole, the apparatus having: a carrier configured to be conveyed through the borehole; a transmitter disposed at the carrier and configured to transmit electromagnetic energy at a first frequency into the formation; a first antenna disposed at the carrier and configured to receive electromagnetic signals from the formation as a result of the transmitted electromagnetic energy interacting with the formation; and an active filter coupled to the antenna and configured to filter electromagnetic signals received by the antenna to let the electromagnetic signals at the first frequency pass for processing to estimate the property.

Abstract: Various embodiments include apparatus and methods of operation with respect to well logging. Apparatus and methods can include a tool having an arrangement of spaced apart transmitter antennas and receiver antennas in transmitter-receiver antenna pairs to make shallow measurements and deep measurements. The signals acquired from the shallow measurements and deep measurements can be processed to provide a look-ahead signal in a drilling operation. The transmitter and receiver antennas can be oriented to cancel or substantially cancel out signals from layers between the transmitter antenna and the receiver antenna in response to the transmitter being operated downhole in a well. Additional apparatus, systems, and methods are disclosed.

Abstract: A method and system to compensate for inaccuracies in crosswell tomography is presented. The method includes obtaining data from at least two receivers in response to transmissions from at least two transmitters. Next, at least one compensated value is derived based on the responses of the receivers to the transmitters. Finally, an inversion is performed based at least in part on the compensated value derived. This method eliminates inaccuracies that can be caused by sensor gain and phase variations in the inversion process. Inversion results with gain and phase compensation produce better imaging results that can better help determine the shape and boundaries of the reservoir.

Abstract: Various embodiments include apparatus and methods to detect and locate conductive structures below the earth's surface. Tools can be configured with receiving sensors arranged to receive signals generated from a conductive structure in response to a current flowing on the conductive structure. Magnetic-related values from the signals can be processed, relative to the tool, to determine a position of a conductive structure from which the signal was generated in response to current flowing on the conductive structure. Additional apparatus, systems, and methods are disclosed.

Abstract: A method and apparatus is provided for collecting reservoir data. The method includes providing one or more electromagnetic sources for generating an electromagnetic field in a reservoir and providing one or more electromagnetic sensors equipped with capacitive electrodes. The electromagnetic source is located separately from the electromagnetic sensor. The electromagnetic sensor may either be located within a well or at the surface, is capable of measuring the electromagnetic field in three dimensions, and may be isolated from the well fluids. The data collected by the electromagnetic sensors can be used to create a model of the oil reservoir, including the water saturation.

Abstract: A method for efficient inversion of measured geophysical data from a subsurface region to prospect for hydrocarbons. Gathers of measured data (40) are encoded (60) using a set of non-equivalent encoding functions (30). Then all data records in each encoded gather that correspond to a single receiver are summed (60), repeating for each receiver to generate a simultaneous encoded gather (80). The method employs iterative, local optimization of a cost function to invert the encoded gathers of simultaneous source data. An adjoint method is used to calculate the gradients of the cost function needed for the local optimization process (100). The inverted data yields a physical properties model (110) of the subsurface region that, after iterative updating, can indicate presence of accumulations of hydrocarbons.

Abstract: A method of measuring a parameter characteristic of a rock formation is provided, the method including the steps of obtaining crosswell electromagnetic signals between two wells and using an inversion of said signals to investigate or delineate the presence of a resistivity anomaly, such as brine in a low resistivity background, wherein the resistivity anomaly is assumed to be distributed as one or more bodies characterized by a limited number of geometrical parameters and the inversion is used to determine said geometrical parameters. The method can also be applied to determine the trajectory of an in-fill well to be drilled.

Abstract: Adsorbed gas in a formation may be estimated. Nuclear magnetic resonance (NMR) data for a subsurface geological formation is obtained, and at least a portion of the NMR data is corrected to produce corrected NMR data. A NMR-based estimate of formation porosity is determined using the corrected NMR data. Dielectric permittivity data for the subsurface geological formation is obtained, and a dielectric permittivity-based estimate of the formation water-filled porosity is determined using the dielectric permittivity data. A gas volume is determined using the determined NMR-based estimate of the formation porosity and the determined dielectric permittivity-based estimate of the formation water-filled porosity. The gas volume may be determined by subtracting the determined dielectric permittivity-based estimate of the formation water-filled porosity from the determined NMR-based estimate of the formation porosity. The gas volume per unit volume of the formation may be determined using an equation of state.

Abstract: A multicomponent induction logging tool uses a nonconducting mandrel. A central conducting member including wires that electrically connect at least one of the antennas to another of the antennas. Electrodes disposed about the transmitter antenna form a conductive path through a borehole fluid to the central conducting member.

Abstract: The present disclosure relates to methods and apparatuses for evaluating fluid saturation in an earth formation using complex dielectric permittivity. The method may include estimating fluid saturation using an estimated rate of change at a frequency of an imaginary part of permittivity relative to a real part of permittivity. The method may include performing dielectric permittivity estimates using an electromagnetic tool in a borehole. The apparatus may include the electromagnetic tool and at least one processor configured to store information obtained by the electromagnetic tool in a memory. The at least one processor may also be configured to estimate the fluid saturation.

Abstract: Disclosed is a method for estimating a pore pressure of an earth formation penetrated by a borehole and an associated uncertainty. The method includes: conveying a carrier through the borehole; performing formation measurements relating to porosity at a plurality of depths in the borehole using a downhole tool coupled to the carrier; defining a first depth interval and a second depth interval deeper than the first depth interval, the first depth interval comprising a first set of formation measurement points and the second depth interval comprising a second set of formation measurement points; establishing a plurality of trendlines of depth versus porosity-related measurements using a processor with each trendline in the plurality of trendlines extending from a point in the first depth interval through a point in the second depth interval; and calculating a pore pressure line and associated uncertainty using the plurality of trendlines.

Abstract: Disclosed is a method of estimating a property of an earth formation penetrated by a borehole. The method includes conveying a carrier through the borehole and performing a plurality of electrical measurements on the formation using a sensor disposed at the carrier and having a plurality of electrodes disposed in a concentric arrangement wherein a standoff distance between the sensor and a wall of the borehole has an influence on each electrical measurement in the plurality of electrical measurements. The method further includes determining an impedance for each electrical measurement in the plurality of electrical measurements and inputting the determined impedances into an artificial neural network implemented by a processor. The artificial neural network outputs the property wherein the outputted property compensates for the influence of sensor standoff distance on each electrical measurement in the plurality of electrical measurements.

Abstract: An electromagnetic (EM) data acquisition method for a geological formation may include operating EM measurement devices to determine phase and amplitude data from the geological formation. The EM measurement devices may include at least one first EM measurement device within a borehole in the geological formation, and at least one second EM measurement device at a surface of the geological formation. The method may further include processing the phase data independent from the amplitude data to generate a geological constituent map of the geological formation, and identifying different geological constituents in the geological constituent map based upon the measured amplitude data.

Abstract: A method, a system, and an apparatus are described for the data acquisition in the well-logging of a borehole wall during the investigation of formation properties. Data acquisition is conducted by either an adaptive phase compensation processing or a modulus mode processing, both of which use in-phase and out-of-phase current components to obtain current values. Adaptive phase compensation employs a calculation of a phase shift compensation value, which may then be applied to subsequent acquisitions and can be further processed in the generation of an image of the borehole wall.

Abstract: Certain embodiments described herein provide an estimate of the magnetic interference incident upon a drilling system using multiple magneticclaim sensors within a downhole portion of the drilling system in a first wellbore. Certain embodiments utilize the magnetic measurements to determine an axial interference resulting from one or more magnetic portions of the downhole portion and to provide an estimate of a relative location of a second wellbore spaced from the first wellbore.

Abstract: Disclosed is an adaptive borehole correction (ABC) technique based on an inversion approach that advantageously corrects shallow laterolog measurements for borehole effects, including determining and accounting for unknown tool eccentricity. The algorithm is based on simplex radial 1-D inversion where at every logging up to four unknowns are determined, namely tool eccentricity, Rt, Rxo, and Lxo. After that a borehole correction methodology is employed wherein the tool response in a borehole with real mud resistivity Rm is modified to a response in the borehole with virtual mud resistivity equal to Rxo.

Abstract: Disclosed is a method for determining calibration factors of an induction tool that includes three receiver coils, each having a distinct orientation. The method includes: placing the induction logging tool in a first position at a first height above a surface of the earth; performing a first set of measurements of conductivity using the receiver coils with the induction logging tool in the first position at the first height; placing the induction logging tool in a second position at a second height above the surface of the earth; performing a second set of measurements of conductivity using the receiver coils with the induction logging tool in the second position at the second height; and determining the calibration factors that correct conductivity measurements performed by the induction logging tool in a borehole penetrating the earth using the first and second sets of measurements.

Abstract: A method for estimating a property of an earth formation penetrated by a borehole includes conveying a drill tubular through the borehole and transmitting a signal into the formation with a transmitter transducer disposed at the drill tubular. The method further includes receiving a first signal with a first receiver transducer having a sensitivity oriented in a first direction and disposed an axial distance from the transmitter transducer and receiving a second signal with a second receiver transducer having a sensitivity oriented in a second direction different from the first direction and disposed an axial distance from the transmitter transducer. The method also includes calculating a corrected signal that corrects for at least one of bending and torsion of the drill tubular between the transmitter transducer and the first and second receiver transducers using the first signal and the second signal and estimating the property using the corrected signal.

Abstract: A method for estimating a fracture aperture in a formation penetrated by a well includes obtaining at least one of a vertical resistivity (Rv) and a horizontal resistivity (Rh) of the formation; obtaining a mud resistivity (Rmud) or a matrix resistivity (Rmatrix); and estimating the fracture aperture. The estimating of the fracture aperture may be performed by solving the following two equations: Rv=Vhf·Rm+(1?Vhf)·Rmatrix and 1/Rh=Vhf·1/Rmud+(1?Vhf)·1/Rmatrix, wherein Vhf is the fracture aperture.

Abstract: A method for increasing sensitivity in a measurement of at least one of magnitude and direction of resistivity in a subsurface material, the method including: performing a first set of measurements of resistivity of the subsurface material using a first logging instrument; constructing a model of a background signal using the first set of measurements; calculating a predicted response of a second logging instrument to the model of the background signal; performing a second set of measurements of at least one of magnitude and direction of resistivity of the subsurface material using the second logging instrument; deriving a second logging instrument response from the second set of measurements; and subtracting the predicted response from the second logging instrument response to produce a corrected response that has greater sensitivity than the second logging instrument response.

Abstract: A method for detecting formation resistivity outside of metal casing using time-domain electromagnetic pulse in a borehole, the method including steps of a) providing a borehole large power pulse transmitting source, recording an induced electromotive force ?, and full time digital recording a transmitted waveform and a received signal; b) conducting transmission-reception and superimposing received signals to improve signal to noise ratio; c) calculating corresponding casing response according to known casing parameters and recorded current waveform of the transmitting source to obtain a relative induced electromotive force ??f; d) correcting relative induced electromotive force value; e) carrying out one-dimensional inversion and converting the observation signal into radial variation information of the formation resistivity; f) obtaining a two-dimensional image of the longitudinal and radial resistivity distribution of outer cased formation resistivity for measured well sections; and g) determining residua

Abstract: A method for determining movement of a fluid contact in a subsurface reservoir includes measuring azimuthally sensitive resistivity at a first time from within a wellbore penetrating the subsurface reservoir. A first position of the fluid contact with respect to the wellbore is determined using the azimuthally sensitive resistivity measurements. After a selected time, the measuring azimuthally sensitive resistivity from within a wellbore penetrating the subsurface reservoir is repeated. Movement of the fluid contact from the first position is determined using the repeated azimuthally sensitive resistivity measurements.

Abstract: Tools, systems, and methods are disclosed for multi-component induction logging with iterative analytical conversion of tool measurements to formation parameters. At least some system embodiments include a logging tool and at least one processor. The logging tool provides transmitter-receiver coupling measurements that include at least diagonal coupling measurements (Hzz, Hxx, and/or Hyy) and cross-coupling measurements (Hxy, Hxz, and Hyz). The processor employs an iterative analytical conversion of the cross-coupling measurements into formation resistive anisotropy and dip information. The processor may further provide one or more logs of the resistive anisotropy and/or dip information.

Abstract: A multi-step electromagnetic inversion method is provided for determining formation resistivity, anisotropy and dip. An electromagnetic logging tool is used to obtain non-directional, anisotropy, and directional (including symmetrized and anti-symmetrized resistivity measurements) in a formation using an electromagnetic logging tool. Bed boundaries of the formation are first identified. A horizontal resistivity profile is obtained using the non-directional resistivity measurements, and a vertical resistivity profile is obtained using the anisotropy resistivity measurements. The vertical resistivity profile is improved using the directional resistivity measurements, while dip values are also obtained via an inversion using the directional resistivity measurements. Then, an inversion for each of vertical resistivity, horizontal resistivity, dip values, and bed boundaries is performed using all of the non-directional, anisotropy, and directional resistivity measurements to obtain a formation model.

Abstract: In electrical resistivity tomography and electrical impedance tomography, interference effects of the metal well casing can be reduced by disposing measurement electrodes in the form of conductive bands around a region of primary insulation on the well casing. Secondary insulation can be provided longitudinally adjacent the primary insulation to further reduce the interference effects. Parameters of the primary and secondary insulation may be determined using finite element methods. The conductive band electrode can connect to a wire of a multi-strand cable using a novel takeout arrangement. Novel measurement methods are also described.

Abstract: An apparatus for measuring formation resistivity and dielectric constant used with a logging tool includes a tool pad coupled to the logging tool, a pair of receivers deployed on the tool pad including a first receiver and a second receiver, a measuring transmitter deployed on the tool pad and at an axial distance from the pair of receivers, and a compensating transmitter deployed on the tool pad and positioned substantially at the midpoint of the pair of receivers. The compensating transmitter transmits compensating signals to the pair of receivers and the measuring transmitter transmits measuring signals to the pair of receivers. The pair of receivers measures the amplitudes and phases of the compensating signals and the measuring signals in a sequential order and computes a compensated amplitude ratio and a compensated differential phase accordingly. A corresponding method for measuring formation resistivity and dielectric constant is also provided.

Abstract: A method of processing electromagnetic signal data includes: disposing a downhole tool in a borehole in an earth formation, the downhole tool including at least one electromagnetic transmitter; performing a downhole electromagnetic operation, the operation including transmitting an electromagnetic pulse from the transmitter into the formation and measuring a time domain transient electromagnetic (TEM) signal over a selected time interval following a transmitter turn-off time; transforming the measured time domain TEM signal into a frequency domain TEM signal measured; and applying an inversion technique to the transformed frequency domain TEM signal to estimate one or more formation parameters.

Abstract: An apparatus for measuring formation resistivity in logging while drilling application includes a tool body, a pair of receivers deployed on the tool body including a first receiver and a second receiver, a measuring transmitter deployed on the tool body and at an axial distance from the pair of receivers, and a compensating transmitter deployed on the tool body and positioned substantially at the midpoint of the pair of receivers. The compensating transmitter transmits compensating signals to the pair of receivers and the measuring transmitter transmits measuring signals to the pair of receivers. The pair of receivers measures the amplitudes and phases of the compensating signals and the measuring signals in a sequential order and computes a compensated amplitude ratio and a compensated differential phase accordingly. A corresponding method for measuring formation resistivity is also provided.

Abstract: A method, a system, and an apparatus are described for the data acquisition in the well-logging of a borehole wall during the investigation of formation properties. Data acquisition is conducted by either an adaptive phase compensation processing or a modulus mode processing, both of which use in-phase and out-of-phase current components to obtain current values. Adaptive phase compensation employs a calculation of a phase shift compensation value, which may then be applied to subsequent acquisitions and can be further processed in the generation of an image of the borehole wall.

Abstract: A method of processing electromagnetic signal data includes: receiving transient electromagnetic (TEM) signal data from a downhole tool disposed in an earth formation, the downhole tool including at least one conductive component; estimating an initial bucking coefficient based on relative positions of the at least two receivers; combining the TEM signal data using the initial bucking coefficient to estimate an initial formation signal; selecting a plurality of bucking coefficient values based on the initial bucking coefficient and estimating a plurality of formation signals, each formation signal corresponding to one of the plurality of bucking coefficients; and selecting an optimal bucking coefficient from one of the initial bucking coefficient and the plurality of bucking coefficients based on the plurality of formation signals, the optimal bucking coefficient providing suppression of parasitic signals due to the at least one conductive component.

Abstract: A method of interpreting petrophysical measurement data include arranging measurements of at least one physical property of formations into a matrix representing the measurements and selecting a range of number of unobserved factors or latent variables for factor analysis. Factor analysis is performed on the measurement matrix and comprises performing factorization of measurements matrix into a number of factors and performing rotation of the factorization results. Whether the factor loadings for each factor have achieved a “simple structure” is determined and either each of the selected number of factors is associated with a physical parameter of the formations, or one is added to the number of factors and factor analysis and rotation are repeated until factor loadings of all factors have achieved “simple structure” such that the each of the number of factors is associated with a physical property of the formations.

Abstract: A method for identifying low resistivity low contrast high temperature high pressure productive subsurface formations rich in acid gases penetrated by a wellbore includes obtaining dielectric permittivity measurements of selected formations adjacent at least part of the wellbore. Nuclear magnetic resonance relaxometry measurements are obtained for the selected formations, the relaxometry measurements being calibrated to identify relaxation times corresponding to acid gases in high humidity at elevated pressure and temperature. Zones are identified for withdrawing formation fluid samples based on the dielectric permittivity and relaxometry measurements.

Abstract: An electromagnetic method for obtaining a dip azimuth angle from downhole electromagnetic measurements includes acquiring electromagnetic measurement data in a subterranean borehole from at least one measurement array. The electromagnetic measurement data is processed by a least squares method to obtain the dip azimuth angle. Related systems and apparatuses are also disclosed herein.

Abstract: A series of scans is generated for a subsurface and a derivative image is created using the series of subsurface images. One or more tests are performed on the derivative image, and a subsurface object is detected based on the one or more tests. A sensor is configured to generate a series of scans for a subsurface and a processor is coupled to the sensor. The processor is configured to execute stored program instructions that cause the processor to generate a series of images of the subsurface using the series of scans, create a derivative image using the series of subsurface images, perform one or more tests on the derivative image, and detect a subsurface object based on the one or more tests.

Abstract: A method of inverting induction logging data for evaluating the properties of underground formations surrounding a borehole, the data including induction voltage measurements obtained from a tool placed close to the formations of interest, the method includes: (a) defining a relationship relating the induction voltage to wave number, dielectric permittivity and conductivity; defining a cubic polynomial expansion of the relationship; and solving the cubic polynomial relationship using the voltage measurements to obtain values for conductivity that includes skin-effect correction, and apparent dielectric permittivity; and (b) using the obtained values for conductivity and apparent dielectric permittivity to derive a simulated value of induction voltage; determining the difference between the simulated value of the induction voltage and the measured induction voltage; and iteratively updating the values of conductivity and dielectric permittivity used for the derivation of the simulated value of induction voltag

Abstract: A method for predicting a pressure window for drilling a borehole in a formation includes: obtaining a pore pressure related data value of the formation using a data acquisition tool; predicting pore pressure uncertainty from the pore pressure related data value of the formation using a processor; estimating uncertainty of a pressure window for drilling fluid using the predicted pore pressure uncertainty using a processor; and applying the estimated uncertainty to the pressure window to provide a modified pressure window using a processor.

Abstract: A system and method for determining formation parameters is provided. The system includes an induction logging tool having a plurality of transmitter coils. The induction logging tool further includes a plurality of receiver coils, each of the receiver coils being spaced apart from the transmitter coils by a predetermined distance and receiving a response signal from the formation. The system includes circuitry coupled to the induction logging tool, the circuitry determining voltages induced in the plurality of receiver coils by the response signal. The circuitry separates real or in-phase portions of the determined voltages from imaginary of ninety degrees out of phase portions of the determined voltages and determines formation parameters using imaginary portions of the measured voltages.

Abstract: Methods and computing systems for processing electromagnetic data are disclosed. In one embodiment, a method is disclosed that includes performing a first controlled source electromagnetic survey at a selected area that includes a reservoir zone; performing additional controlled source electromagnetic surveys at the selected area after the first survey; and inverting measurements from the first survey and the additional surveys to identify at least one resistivity change in the reservoir zone after the first survey, wherein during the inversion, respective measured resistivity values from the first survey and respective measured resistivity values from the additional surveys are constrained to be constant, and correspond to one or more areas disposed in the selected area that are outside of the reservoir zone.

Abstract: A method and apparatus for removing drift from a curve of raw data acquired from a wellbore that intersects a subterranean formation. The raw data curve is filtered to remove DC components, integrating the filtered curve generates a new baseline curve. Adding the new base line curve to the filtered curve yields a corrected curve that is used to extract drift from the raw data curve. The corrected curve is filtered and then subtracted from the raw data curve to produce a drift curve. A data curve, absent any drift, is generated by filtering the drift curve, and subtracting the filtered data curve from the raw data curve.

Abstract: The method of the invention comprises the following steps: positioning a field source (40) at at least one first distance from a target volume (10); positioning a field receiver (50) at at least one second distance from same target volume (10); for each couple of first and second distance, determining a measured signal Smes and a simulated signal Ssim; determining values of physical parameters of same target volume (10) by minimizing a function depending on the measured Smes and simulated signals Ssim. The method of the invention is characterized in that when determining a simulated signal Ssim, specific global reflection coefficients and receiver-receiver functions are introduced in feedback loops.

Abstract: The present disclosure relates to methods and apparatuses for evaluating an earth formation using complex dielectric permittivity. The method may include estimating at least one property of the earth formation using a real part and an imaginary part of complex permittivity at a plurality of frequencies. The at least one property may include one or more of: oil viscosity and surface tension of a water-oil system. The method may include performing dielectric permittivity estimates using an electromagnetic tool in a borehole. The apparatus may include the electromagnetic tool and at least one processor configured to store information obtained by the electromagnetic tool in a memory. The at least one processor may also be configured to estimate at least one property of the earth formation.

Abstract: A technique provides a methodology for improving surveys of subterranean regions. The methodology comprises estimating macro anisotropy and an intrinsic or micro anisotropy of an overburden. A surface electromagnetic survey is conducted, and the data from the survey is inverted based on or including information gained from estimating the macro anisotropy and/or intrinsic anisotropy. A processor system can be used to conduct the inversion with the adjustments for anisotropy to improve the information provided by the survey.

Abstract: A method for estimating at least one formation parameter from a directional resistivity measurement includes computing a plurality of hypothetical directional resistivity values at a corresponding plurality of formation parameter values. The computation makes use of a forward model having at least one analytical expression that relates a directional resistivity measurement to the formation parameter. The analytical expression includes at least one image source term. Comparison of computed directional resistivity values with measured direct resistivity values enables a value of at least one formation parameter to be selected. The method may be implemented on a downhole processor.

Abstract: A method of determining anisotropy in a borehole is disclosed. An array of measurements along the borehole is obtained and a first depth in the borehole is selected. An arbitrary plane oriented with respect to the borehole at the first depth is designated and an anisotropy for the first depth with respect to the arbitrary plane is determined. The arbitrary plane is repositioned at the first depth and an anisotropy for different positions of the arbitrary plane at the first depth is determined. A minimum anisotropy coefficient with respect to the arbitrary plane at the first depth is identified based on anisotropy for different positions of the arbitrary plane. An anisotropy tensor for the first depth is then identified.

Abstract: A method of processing azimuthal measurement data includes: receiving a plurality of data values generated by a rotating measurement tool, the measurement tool including at least one measurement sensor and configured to rotate and measure a signal at each of a plurality of azimuthal orientations; associating each received data value with an azimuthal orientation; selecting one or more data values that provide sufficient information regarding a measured signal, each of the selected data values having an associated azimuthal orientation; disregarding azimuthal orientations associated with one or more data values that provide insufficient information regarding a measured signal; and fitting only the selected data values to a sinusoidal curve.

Abstract: The disclosure relates to an apparatus and a method for well logging as well as a data processing device thereof. Said apparatus for well logging comprises a drill collar body and an array of antennas, wherein said array of antennas comprises at least a pair of transmitting antenna and receiving antenna, said transmitting antenna and receiving antenna are configured for generating a curve of axial forward depth of investigation. By employing the method for well logging according to the present invention, not only the variation of resistivity in the axial forward formation may be measured in real time during the drilling, but also the interfacial characteristics of the axial forward formations having different resistivity may be discriminated during drilling.

Abstract: To update a subterranean model, an initial subterranean model is provided, and based on the initial subterranean model, changes to subterranean parameters are predicted using a reservoir simulator. Electromagnetic data representing characteristics of a subterranean structure is computed according to the predicted changes to the subterranean parameters, and the initial subterranean model is modified based on comparing the computed electromagnetic data with observed electromagnetic data.

Abstract: Various embodiments include apparatus and methods to operate an induction measurement process in a borehole that addresses direct coupling of a signal between sensors of a measuring tool. Apparatus and methods can include a processing unit to generate formation parameters from signals received in the measurement tool. Additional apparatus, systems, and methods are disclosed.

Abstract: A method of passive surveying comprises generating one or more detected signals by passively detecting a signal generated within a subsurface earth formation due to a seismoelectric response or an electroseismic response in at least one porous subsurface earth formation containing at least one fluid, and processing the one or more detected signals to determine at least one property of the subsurface earth formation.

Abstract: A Bayesian methodology is described for designing experiments or surveys that are improved by utilizing available prior information to guide the design toward maximally reducing posterior uncertainties in the interpretation of the future experiment. Synthetic geophysical tomography examples are used to illustrate benefits of this approach.