Halliburton Energy Services, Inc.

Baker Hughes Corporation

Western Atlas International, Inc.

Jiaqi Xiao

Li Gao

Otto N Fanini

Liming Yu

Ingo M Geldmacher

Michael S Bittar

David R Beard

Gulamabbas A Merchant

Berthold Kriegshauser

Bill H Corley

Qiang Zhou

Berthold Kriegsh&auml;user

Logging tools, methods, and computer programs for use in borehole logging are described. The logging tool includes three or more tensors, each tensor including one or more coils. Each coil is characterized by coil parameters including an axis orientation, a cross-sectional area, a number of turns, and a location. At least one of the coil axes is disposed at an angle to the borehole axis. One or more of the coil parameters are selected to minimize sensitivity to borehole current.

Minimizing the effect of borehole current in tensor induction logging tools

A method and related system for correcting measurements obtained from an induction logging device. In one embodiment, the method comprises: receiving conductivity measurements from a multi-array induction tool; constructing a measurement pattern vector from the conductivity measurements; determining one or more geometry parameters associated with an approximation of the measurement pattern vector; finding borehole geometrical factors using current values of the one or more conductivity parameters and of the one or more geometry parameters; and calculating improved estimates of the one or more conductivity parameters using current values of the borehole geometric factors. The geometry parameters may be determined by finding a geometry pattern vector that best fits the measurement pattern vector. The determining, finding, and calculating operations may be repeated until a predetermined condition is satisfied. Finally, the conductivity measurements may be corrected for environment effects using calculated conductivity parameters and geometry parameters.

System and method for correcting induction logging device measurements by alternately estimating geometry and conductivity parameters

A method and apparatus for minimizing direct coupling between transmitters and receivers on a downhole logging tool are disclosed. One embodiment includes a transmitter, a bucking device, and a plurality of receivers, where signals may be directly coupled from the transmitter into the receivers and signals may be indirectly coupled from the transmitter into the receivers through the formation and borehole environment. The bucking device minimizes the magnitude of the signals that are directly coupled from the transmitter into multiple receivers within the plurality. By varying the current in the bucking device, the bucking device minimizes the magnitude of the directly coupled signal of each receiver in the plurality, and each receiver may utilize a common bucking device.

Method and apparatus for minimizing direct coupling for downhole logging devices

A system and method of correcting skin effect of conductivity measurements made by electromagnetic induction well logging instruments. A limited number of measurements using different frequencies may be used. The skin effect correction system and method is capable of processing a complex signal waveform but only requires the in-phase signal measurements which are then corrected for the skin effect value and the geometric factors of the apparent conductivity measurements, thus making the corrected measurements suitable for advanced processing with modern array-type induction logging tools.

Induction logging system and method featuring multi-frequency skin effect correction

Method and apparatus for deriving information regarding a subsurface geophysical formation. Well logging data is acquired for the subsurface geophysical formation. Geometrical parameters for the subsurface geophysical formation are determined by inversion processing of the acquired well logging data in a pattern space while formation conductivities for the subsurface geophysical formation are determined by inversion processing of the acquired well logging data in a measurement space. The processing may be iteratively applied until satisfied formation parameters are achieved.

Method and apparatus for inversion processing of well logging data in a selected pattern space

Data are acquired using multi-array logging tool in a borehole having an angle of inclination to a normal to the bedding plane of earth formations. The multi-array measurements are filtered using angle dependent filters to give a filtered curve corresponding to a target one of the multi-array measurements using angle dependent filters. Correlation coefficients are determined for a set of possible dip angles and a relative dip angle is estimated from the correlation coefficients. This dip angle estimate together with bed boundaries obtained from the multi-array measurements are used for inverting multi-component measurements alone or jointly with multi-array measurements to refine the relative dip angle interpretation and give horizontal and vertical formation resistivity.

Method for joint interpretation of multi-array induction and multi-component induction measurements with joint dip angle estimation

Induction and other resistivity well logging tools determine formation conductivity at various depths but these measurements contain pronounced errors when the tool is proximate to an inclined underground bed boundary. A method to correct tool measurements includes calculating an expected tool response at a relative dip angle of zero degree and at a particular depth based on an earth model of the underground formation. An expected tool response at the known dip is then calculated. Comparing the calculated zero-dip response with the calculated non-zero-dip response yields the dip effect. A response is also modeled to exclude the non-linearity of the shoulder effect. Comparing the calculated linear response (obtained, e.g. by the Born approximation) with the calculated zero-dip response yields the nonlinear shoulder effect. The nonlinear shoulder effect and/or the dip effect may then be corrected for by subtracting them from the raw or pre-processed measurements.

Method for asymptotic dipping correction

Measurements made by a multicomponent logging tool in a borehole are inverted to obtain horizontal and vertical resistivities of a formation traversed by the borehole. The model includes layers of equal thickness, each layer having a horizontal resistivity and a vertical resistivity. For a vertical borehole, the inversion is done by first iteratively obtaining the horizontal resistivities of the layer using the H component of the data wherein in successive steps of the iteration, the horizontal resistivity for each layer is multiplied by a ratio of a model H output to the measured H . The vertical resistivity model is set equal to the derived horizontal resistivities and the iterative process is repeated using the ratio of the model H output to the measured H . A similar process is used for boreholes with a known inclination. For such an inclined borehole, the two horizontal components H and H are summed to give a horizontal measurement H that is independent of tool rotation. The first step uses a ratio of the model H output to the measured H data to obtain an apparent resistivity, and, in the second step, the ratio of the model H output and the measured H data are used along with a known relationship between the apparent resistivity and the horizontal and vertical resistivities in an iterative manner. No Jacobians or gradients are necessary in the method, so that computational times are small relative to prior art gradient methods.

Vertical 1-D inversion with thin layers of equal thickness

A method of focusing the measurements from an array type induction logging tool using an inhomogeneous background rather than a homogeneous background. A modeled inhomogeneous background response can be separated from the measured response and focused directly using focusing target functions. The residue, the difference between the measured response and the background response, can then be focused using conventional linear focusing methods. A final focusing response is obtained by adding the two focusing responses.

Inhomogeneous background-based software focusing method for array-type induction logging tools

A method for enhancing the axial resolution of conductivity well log measurements of in earth formation zones radially distal from a wellbore. The method includes calculating differential axial resolution information present in measurements of the conductivity of a zone radially proximal to the wellbore by low pass filtering the proximal zone measurements so as to have the same axial resolution as the measurements of earth formations radially distal from the wellbore, and subtracting the low pass filtered measurements from the measurements of the proximal zone. The differential axial resolution information is projected to conductivity values which would obtain if the proximal zone conductivity were equal to the distal zone conductivity. The projection is calculated by determining a projection factor, which is related to a weighted average of a ratio of conductivity in the distal zone with respect to the conductivity in the proximal zone. The projected differential axial resolution information is then added to the conductivity measurements of the distal zone to obtain higher resolution measurements of conductivity in the radially distal zone.

Axial resolution enhancement method for resistivity well logs which

A method for correcting response of an induction logging instrument for inclination of earth formations with respect to an axis of the instrument. The instrument has a transmitter and a plurality of receivers at spaced apart locations. The method includes calculating expected receiver responses of simulated media having different conductivities. The calculations are performed for a plurality of different inclinations. The calculations are also performed for media having a plurality of different conductivity contrasts. 2-dimensional filters corresponding to a charge effect portion of each of the expected responses are calculated. 2-dimensional filters corresponding to a volumetric effect portion of each of the expected responses are calculated. An angle of inclination of the earth formations with respect to the instrument is determined. An approximate conductivity contrast of the earth formations is determined. Coefficients are interpolated between the 2-dimensional charge effect filters having simulated inclinations and contrasts closest to the angle of inclination and conductivity contrast of the formations. The interpolated filter coefficients are applied to measured receiver responses, generating charge effect-filtered measured responses. Coefficients are interpolated between the 2-dimensional volumetric effect filters having simulated inclinations and conductivity contrasts closest to the angle of inclination and conductivity contrast of the formations. The interpolated coefficients are applied to the charge effect-filtered measured responses to calculate corrected receiver responses.

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Houston, TX, United States of America

Jiaqi Xiao