Abstract: Measurements made with an induction logging tool are processed to provide a resistivity model of fluid invasion of the formation. Up to five zones can be determined over a radial distance of about 0.6 m. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A method of analysing results from an electromagnetic survey of an area that is thought or known to contain a subterranean resistive or conductive body within a background strata configuration is described. The method comprises providing a set of electromagnetic field data obtained using at least one electromagnetic receiver and at least one electromagnetic source for a range of source-receiver separations, e.g. providing conventional controlled-source electromagnetic survey data. A subset of the electromagnetic field data is identified that comprises data obtained for source-receiver separations greater than a selected threshold offset. The threshold offset is chosen so that data beyond this offset are characteristic of magnetotelluric data. Thus the subset of data is then processed in accordance with a first technique to obtain information on the background strata configuration.

Abstract: Characterizing a reservoir with electromagnetic imaging surveys includes normalizing measured voltage data by transmitter moment, sorting the normalized voltage data into common receiver profiles, densely resampling transmitter locations using common positions for the receiver profiles, coarsely resampling the data at discreet transmitter locations, defining a starting model for inversion, weighting the data by a factor, converting the normalized voltage data to ratios, calculating a conductivity image using a ratio inversion method, and verifying that an inversion has converged and the image is geologically reasonable. The image can then be displayed. The invention can be used for cross-well, surface-to-borehole, and borehole-to-surface measurements by which the effects of steel casing are reduced.

Abstract: A logging-while-drilling system for efficiently providing a reliable measurement of various petrophysical properties of subsurface earth formations.

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. This invention also relates to a method and apparatus for steering a downhole tool during a drilling operation in order to maintain the borehole within a desired earth formation.

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. Although this invention is primarily intended for MWD or LWD applications, this invention is also applicable to wireline and possibly other applications.

Abstract: Method for completely specifying orientation of electromagnetic receivers dropped to the ocean bottom in an electromagnetic survey. Survey data are selected, rejecting noisy data with long offsets and data where the receiver has saturated with short offsets (61). A model is developed comprising three independent receiver orientation angles completely specifying the receiver orientation in three dimensions, and an earth resistivity model including a water layer and possibly an air layer (62). Maxwell's equations, applied to the model and the selected data, are then inverted to determine the receiver orientations (63).

Abstract: Resistivity measurements at different radial depths of investigation obtained from time lapse resistivity data gained from multiple passes of a resistivity tool through a borehole are analyzed together to obtain indications of at least one of fractional flow, residual oil and water saturations, oil saturation, and water saturation in a formation. For each of the logging passes having resistivity measurements with multiple radial depths of investigation, filtrate loss into the formation is also obtained through joint inversion.

Abstract: A method of locating a conductive target from a wellbore includes generating a current flowing across an insulated gap in a downhole tool positioned in the wellbore, measuring an azimuthal magnetic field with at least one external magnetometer located proximate the exterior of the downhole tool, measuring a secondary magnetic field using a magnetometer disposed inside the downhole tool, computing at least one of a direction and a distance to the conductive target.

Abstract: Characterizing a reservoir with electromagnetic imaging surveys includes normalizing measured voltage data by transmitter moment, sorting the normalized voltage data into common receiver profiles, densely resampling transmitter locations using common positions for the receiver profiles, coarsely resampling the data at discreet transmitter locations, defining a starting model for inversion, weighting the data by a factor, converting the normalized voltage data to ratios, calculating a conductivity image using a ratio inversion method, and verifying that an inversion has converged and the image is geologically reasonable. The image can then be displayed. The invention can be used for cross-well, surface-to-borehole, borehole-to-surface, and single-well (borehole-to-borehole) measurements by which the effects of steel casing are reduced.

Abstract: A method for correcting a measurement of a property of a subsurface material includes: selecting an instrument that includes a test circuit and a separate sensor, the sensor adapted for transmitting an electric signal into the subsurface material and receiving a data signal from the subsurface material, wherein the test circuit and the sensor are switchably coupled to an electronics unit of the instrument; receiving the electric signal from the test circuit in the electronics unit; using the electronics unit, measuring at least one output characteristic of the instrument; and applying a correction to the data signal according to the measured output characteristic. An instrument and an additional method are provided.

Abstract: A method of analyzing results from an underwater controlled source electromagnetic (CSEM) survey of an area that is thought or known to contain a subterranean hydrocarbon reservoir is described. The method is based on a wavefield extrapolation of narrow-band electromagnetic field data obtained from pairs of source and receiver locations. The data comprise a plurality of discrete frequencies between 0.01 Hz and 60 Hz. The wavefield extrapolation is performed for each of these discrete frequencies to provide distributions of electromagnetic scattering coefficient as a function of position and depth beneath the survey area. These distributions may then be combined to provide a displayable image of electromagnetic scattering coefficient. The method is able to quickly provide a displayable image that is readily interpretable.

Abstract: A method for imaging a geologic deposit using data collected from a borehole includes: selecting an instrument for performing electromagnetic (EM) measurements, the instrument including at least one transmitter and at least one orthogonally oriented receiver; obtaining EM measurement data from the borehole with the instrument; transforming the EM measurement data to acoustic data; and estimating at least one of a direction and a distance from the instrument to the deposit from the data. A computer program product and a system are provided.

Abstract: The method for correcting the phase of measured electric signals or magnetic signals of field data from a controlled source electromagnetic survey (CSES) by comparing the measured field data corresponding to a selected frequency to the simulated data for various signal source receiver offsets (71) and correcting the phases of the actual data based on the phase difference for a selected range of small signal offsets (76) based on a go-electric model.

Abstract: Method and computer program for accepting controlled-source electromagnetic (“CSEM”) source and receiver data (40) as time series, transforming these data into the time-frequency domain, and reducing these data and survey metadata to a form suitable for interpretation or inversion. The invention includes: a number of processing tools or programs (30), each designed to take a specific action on CSEM data or metadata, combine data types in some way, and/or provide a visual representation of data; a Graphical User Interface (32) to specify the action of specific tools (34) on specific data, supply parameters to tools, and monitor progress of the processing project; and a specified common internal data format, so that processing tools may be applied in various orders (36) during different processing flows and processed CSEM data can be passed on to interpretation or inversion systems.

Abstract: A method to determine a parameter of a subsurface formation such as anisotropy and dip comprises making at least two cross dipole measurements and forming an anti-symmetrized combination from the at least two cross dipole measurements.

Abstract: A method for tracking a sinusoidal electromagnetic signal in noisy data using a Kalman filter or other tracking algorithm. The method is useful for controlled source electromagnetic surveying where longer source-receiver offsets can cause the source signal to decay significantly and be difficult to retrieve from magnetotelluric or other electromagnetic background.

Abstract: The invention discloses a method for determining the wettability of an underground formation traversed by a borehole, the method comprising: determining the critical water fraction of the underground formation; determining the critical water fraction of the underground formation taken entirely oil-wet, which is called the oil-wet critical water fraction; and combining the critical water fraction and the oil-wet critical water fraction in order to determine the wettability of the underground formation.

Abstract: A method and system for characterization of fault conditions within a subterranean volume. In one embodiment, the system comprises means for mathematically modeling stress conditions, to predict breakout conditions along a borehole trajectory. The system further comprises means for sensing actual breakout conditions along the borehole . Predictive breakout data is compared with sensed breakout conditions to assess correlation between predictive data and actual data, verifying the accuracy of the stress model. The mathematical model may be revised to reflect the presence of an active fault plane in the volume, the presumed fault plane not being intersected by the borehole. The revised model is used to generate new predictive data. Revising the stress model and assessing correlation between predictive and actual breakout conditions is repeatable to achieve an optimally accurate stress model reflecting fault conditions proximal to but not necessarily penetrated by the borehole.

Abstract: A method for estimating a property downhole is provided, which, in one aspect, may include receiving a core at a receiving end of a downhole tool while removing a portion of the received core distal from the receiving end of the tool, obtaining measurements by a sensor downhole, and processing the measurements to estimate the property of interest.

Abstract: A method for measuring electromagnetic wave resistivity of earth formations is provided. The method uses electric field and magnetic field sensors in conjunction with a data collecting system to obtain data samples from strata, determine certain parameters associated with the data samples, such as a depth coefficient and a surface-layer depth coefficient, establish an observational reference frame based upon an equation defined by the stratum depth (H) and propagation frequency (F) and an equation defined by the electromagnetic wave resistivity (?) and stratum depth (H), and utilizes the reference frame to record results from a system configured for continuously measuring the electromagnetic wave resistivity of earth formations. The method uses actual data to determine the relationship between the stratum depth (H) and propagation frequency (F), which makes the resistivity of earth formations the only variable to be measured and thus significantly improves the accuracy of depth measurements.

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 non-lineal statistical independent component (ICA) analysis methodology for calculating T2 or T1 distributions of nuclear magnetic resonance logs. In one aspect, the invention employs a classical blind source separation (BSS) approach with the input data (T2 or T1 distributions) being considered not only horizontally (in relaxation time units), but also vertically (in depth). The statistical variations are used for separating the principal independent components and their corresponding weighting matrix. The result of such ICA based BSS is an efficient separation of T2 components correlative to the presence of particular conditions (e.g., clay bound water, heavy oil, capillary bound water, free water, mud filtrate (water and oil), and noise). Individual saturation of estimated fluids can be calculated from the weighting matrix generated in accordance with the invention.

Abstract: Multicomponent induction measurements are used to estimate horizontal and vertical resistivities of an earth formation. From these resistivity estimates, Net/gross sand thicknesses may be estimated. These are indicative of the position of the well within a deep water channel sequence. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A method and a computer program product for estimating the true intrinsic relaxation time T2 and the internal gradient Gint for a multi-frequency nuclear magnetic resonance imaging tool for well logging includes providing at least two frequencies in a plurality of echo trains, evaluating the signal decay in each echo train, quantifying the signal decay and correlating the signal decay to the internal gradient.

Abstract: An apparatus used in electrical investigation of geological formations GF surrounding a borehole BH, comprises: an electrically conductive body 102 movable through the borehole BH, at least one first transmitter T1 for inducing a first current from a first transmitter position and traveling in a path that includes a first portion of the body and a selected zone SZ of the geological formations GF, at least one second transmitter T2 for inducing a second current from a second position and traveling in a path that includes a second portion of the body and the selected zone SZ, the second transmitter T2 position being different from the first transmitter T1 position on the body, at least a first M0, second M1 and third M2 axial current sensors for measuring a first, a second and a third axial current flowing along the body, respectively, the first, second and third axial current sensor position on the body being different from each other, and at least one lateral current sensor R2 disposed on the body for meas

Abstract: A computer program product includes machine readable instructions stored on machine readable media, the instructions for correlating nuclear magnetic resonance (NMR) well logging data with other well logging data, the product including instructions for: receiving the NMR well logging data; receiving the other well logging data; determining a tendency of the NMR logging data to correlate with the other logging data and providing output including correlation information. A system is also provided.

Abstract: Neural networks may be used to determine and predict formation dip angles and perform quality assurance assessments from data collected with a multi-component induction tool used for well logging. The neural networks make use of corrected, rotated and normalized data to provide the predictions and assessments. Synthetic data using various models is used to train the neural networks. The teachings herein provide for real-time determinations with a substantial degree of accuracy in the results.

Abstract: A computer program product includes machine readable instructions stored on machine readable media, the instructions for correlating nuclear magnetic resonance (NMR) well logging data with other well logging data, the product including instructions for: receiving the NMR well logging data; receiving the other well logging data; determining a tendency of the NMR logging data to correlate with the other logging data and providing output including correlation information. A system is also provided.

Abstract: A method of locating a conductive target from a wellbore includes generating a current flowing across an insulated gap in a downhole tool positioned in the wellbore, measuring an azimuthal magnetic field with at least one external magnetometer located proximate the exterior of the downhole tool, measuring a secondary magnetic field using a magnetometer disposed inside the downhole tool, computing at least one of a direction and a distance to the conductive target.

Abstract: A pseudo-image is produced by combining deep-reading azimuthally sensitive resistivity measurements with azimuthally insensitive resistivity measurements made by a multiple propagation resistivity tool. This image is useful in reservoir navigation. Features on the azimuthally sensitive measurements such as saddle-points and mid-points are diagnostic of bed geometry relative to the borehole.

Abstract: To characterize an earth subterranean structure using a measurement assembly including electromagnetic (EM) receivers and one or more EM sources, measured voltage data collected by EM receivers in response to transmission by one or more EM sources is received. Based on a model, predicted EM data is computed. Inversion is iteratively performed according to a function that computes a difference between the measured voltage data and a product of a term containing the predicted EM data and a term containing distortion data that accounts at least for distortion effect by an environment of the measurement assembly. The inversion is iteratively performed to solve for parameters of the model and the distortion data.

Abstract: Method for determining time-dependent changes [73] in the earth vertical and horizontal electrical resistivity and fluid saturations from offshore electromagnetic survey measurements. The method requires both online and offline data, which should include at least one electromagnetic field component sensitive at least predominantly to vertical resistivity and another component sensitive at least predominately to horizontal resistivity [62]. Using a horizontal electric dipole source, online Ez and offline Hz measurements are preferred. For a horizontal magnetic dipole source, online H2 and offline E2 data are preferred. Magnetotelluric data may be substituted for controlled source data sensitive at least predominantly to horizontal resistivity. Maxwell's equations are solved by forward modeling [64,65] or by inversion [66,67], using resistivity models of the subsurface that are either isotropic contrast, and [64,66] or anisotropic [65,67].

Abstract: Characterizing a reservoir with electromagnetic imaging surveys includes normalizing measured voltage data by transmitter moment, sorting the normalized voltage data into common receiver profiles, densely resampling transmitter locations using common positions for the receiver profiles, coarsely resampling the data at discreet transmitter locations, defining a starting model for inversion, weighting the data by a factor, converting the normalized voltage data to ratios, calculating a conductivity image using a ratio inversion method, and verifying that an inversion has converged and the image is geologically reasonable. The image can then be displayed. The invention can be used for cross-well, surface-to-borehole, and borehole-to-surface measurements by which the effects of steel casing are reduced.

Abstract: Cross-component measurements made with a dual-transmitter configuration are processed to estimate a distance to an interface in an anisotropic earth formation. Optionally, measurements may be made with two receivers, also in the dual transmitter configuration.

Abstract: Measurements made by a four terminal resistivity imaging tool in a borehole using a voltage measurement device with two different input impedances. From the two measurements, formation resistivity is determined with minimal sensitivity to standoff. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A method for determining reservoir formation properties that consists of exciting the reservoir formation with an electromagnetic exciting field, measuring an electromagnetic signal produced by the electromagnetic exciting field in the reservoir formation, extracting from the measured electromagnetic signal a spectral complex resistivity as a function of frequency, fitting the spectral complex resistivity with an induced polarization model and deducing the reservoir formation properties from the fitting with the induced polarization model.

Abstract: A method for correcting induction conductivity well log measurements for conductivity of a wellbore and a formation proximate the wellbore includes estimating an effective formation conductivity for the formation proximate the wellbore from measurements made by an induction receiver proximate an induction transmitter. The effective formation conductivity is used to correct apparent conductivity measurements made by at least one induction receiver on the instrument.

Abstract: A resistivity imaging apparatus includes: a first sensor electrode disposed on an electrode pad and positioned at a first standoff; a second sensor electrode disposed on the electrode pad and adjacent the first sensor electrode, the second sensor electrode positioned at a second standoff; and a return electrode disposed on the electrode pad, wherein the sensor electrodes and the return electrode are configured for injecting current into a formation and receiving a signal from the formation. Other embodiments, methods and computer program products are disclosed.

Abstract: A method for determining a list of survey points for a drilling well includes a feedback loop in which one or more measured parameters are compared with computed or derived parameters. The computed parameters are typically obtained from other/additional measurements. For example, in one exemplary embodiment of the invention, a magnetic least distance vector determined via magnetic ranging is compared with a geometric least distance vector computed from conventional borehole surveying measurements. Estimates of the drilling well azimuth and/or inclination may be adjusted to yield a good agreement between the magnetic and geometric least distance vectors. Exemplary embodiments of the present invention advantageously provide for a substantially real-time determination of a definitive well path for a drilling well as well as a substantially real-time relative placement of the drilling well with respect to a target well.

Abstract: Oil-based mud imaging systems and methods having leakage current compensation. In some embodiments, disclosed logging systems include a logging tool in communication with surface computing facilities. The logging tool is provided with a sensor array having at least two voltage electrodes positioned between at least two current electrodes that create an electric field in a borehole wall, and is further provided with electronics coupled to the current electrodes to determine a differential voltage between the voltage electrodes in response to different current frequencies from the current electrodes. From the voltage measurements at different frequencies, the computing facilities determine borehole wall resistivity as a function of depth and azimuth, and may display the resistivity as a borehole wall image.

Abstract: A method for determining fluid saturation in a formation at a plurality of radial depths near a wellbore, the method including: obtaining multi-frequency nuclear magnetic resonance (NMR) response data for the formation; and processing the data to determine simultaneously the fluid saturation at each radial depth. A computer program product is provided.

Abstract: A tool for performing electromagnetic measurements within a borehole includes a transmitter including a coil having N-turns wound coaxially around a long metallic mandrel and a receiver including a coil having a one-turn receiving loop wound coaxially around the mandrel; wherein the transmitter is adapted for providing a current I of a predetermined frequency ƒ of a maximum intensity in a predetermined part of a near borehole zone; and wherein the receiver is disposed a distance L from the transmitter and adapted for receiving a signal from the transmitter. A method for use of the tool is provided.

Abstract: Disclosed is a method and apparatus for measuring the electromagnetic wave resistivity of earth formations. The disclosed method and apparatus use an electric field sensor, a magnetic field sensor in conjunction with a data collecting system to obtain data samples from strata, determine certain parameters associated with the data samples, such as a depth coefficient and a surface-layer depth coefficient, establish an observational reference frame based upon an equation defined by the stratum depth (H) and propagation frequency (F) and an equation defined by the electromagnetic wave resistivity (?) and stratum depth (H), and utilize the reference frame to record results from a data collecting, controlling, storing and processing system configured for continuously measuring the electromagnetic wave resistivity of earth formations.

Abstract: Methods and apparatus are provided for receiving, detecting and transmitting geophysical data from a plurality of electrodes placed in the soil utilizing a dynamically reconfigurable wireless control unit that is located on each electrode. Data from the control units is transmitted by a wireless signal to a centralized data processor for analysis. Control data is provided from a central control processor to the control unit by wireless transmission. The control unit, which is positioned, includes a multi-channel radio frequency transmitter/receiver and a processor to actuate relays and record data returns from the measured substrate soil for transmission to the central data processor. The control unit incorporates a changeable code or address to unambiguously identify itself, and its spatial relationship to other electrodes, to the central data processor and the central control processor.

Abstract: A data compression technique for MWD applications uses feature detection, extraction, followed by image compression for only the region(s) of interest. The detection approach processes data in real time. It triggers on the start and end of a feature without processing any further features. This provides feature detection with zero latency. Compressing only the region of interest provides data compression with both higher resolution and higher compression ratio.

Abstract: Measurements made by a multi-component logging tool in a borehole are inverted to obtain three principal resistivities (or conductivities) and three associated angles of a bi-axially symmetric formation traversed by the borehole.

Abstract: Resistivity measurements at different radial depths of investigation obtained from multiple passes of a resistivity tool through a borehole are analyzed together to obtain indications of at least one of fractional flow, oil saturation, and water saturation in a formation.

Abstract: Techniques for calibrating an electromagnetic logging tool equipped with a plurality of antennas, with at least one antenna having its axis at an angle with respect to a tool axis, include disposing a test loop about the tool such that an axis of the tool and a plane on which the test loop lies form a tilt angle that is between about 0 and 90 degrees. An induced signal is measured at one of the antennas by energizing another of the antennas. Embodiments analyze the induced signal corresponding to a max or min extrema associated with a coupling effect due to the test loop. In other embodiments a corrected signal is compared with a calculated signal.

Abstract: Systems and methods for determining in-situ hydrate saturation of hydrate-bearing formations using dielectric properties of gas hydrate amounts are described. In accordance with one aspect, a method for determining gas-hydrate saturation concentration of hydrate-bearing formations includes collecting data using a dielectric propagation tool indicative of propagation time (tpl) and attenuation time (?), collecting data indicative of density using a density device, and processing the combination of data indicative of tpl, ? and density to determine the concentration of gas-hydrate saturation and porosity of the formations.