177 results about "Induction logging" patented technology

A directional induction logging tool is provided for measurement while drilling. This tool is preferably placed in a side pocket of a drill collar, and it comprises transmitter and receiver coils and an electromagnetic reflector. The reflector, which may be a layer of highly conductive material placed between the coils and the body of the drill collar, serves to focus the electromagnetic fields generated and sensed by the tool in the direction away from the reflector, thus providing a directional response to formation conductivity with a relatively high depth of investigation. In preferred embodiments of the invention, magnetically permeable cores are placed within the coils to concentrate the magnetic fields that pass through them. Circuitry is described for balancing the mutual inductive coupling of the coils by injecting a direct current signal through one or more of the coils, which alters the magnetic permeability of the core material. The magnitude of the direct current required to achieve a balanced condition may be derived from the quadrature phase component of the return signal. Circuitry is also provided for generating a transmitted signal and for processing the return signals, including digital-to-analog conversion circuitry for providing digital data for transmission to the surface. This tool may be employed to provide real-time directional conductivity information that may be used to detect and follow bed boundaries in geosteering operations.

A method is provided for determining an electric conductivity of an earth formation formed of different earth layers, which earth formation is penetrated by a wellbore containing a wellbore fluid, is provided. The method includes the steps of: lowering an induction logging tool into the wellbore to a location surrounded by a selected one of the earth layers, the tool having a magnetic field transmitter effective to induce magnetic fields of different frequencies in the earth formation, and a magnetic field receiver effective to receive response magnetic fields and to provide a signal representative of each response magnetic field, at least one of the transmitter and the receiver having a plurality of magnetic dipole moments in mutually orthogonal directions. At least two of the different frequencies are selected, and for each selected frequency, the transmitter is operated so as to induce a magnetic field in the earth formation and the receiver is operated so as to provide a signal representing a response magnetic field, wherein the at least one of the transmitter and receiver is operated in the mutually orthogonal directions. The signals are combined in a manner so as to create a combined signal having a reduced dependency on the electric conductivity in the wellbore region. The formation resistivity and the relative orientation of the logging tool with respect to the formation layering is determined from the combined signal.

Measurements made by a multicomponent logging tool in a borehole are inverted to obtain horizontal and vertical resistivities and formation dip and azimuth angles of a formation traversed by the borehole. The inversion is performed using a generalized Marquardt-Levenberg method. In this generalized Marquardt-Levenberg method, a data objective function is defined that is related to a difference between the model output and the measured data. The iterative procedure involves reducing a global objective function that is the sum of the data objective function and a model objective function related to changes in the model in successive iterations. In an alternate embodiment of the invention, the formation azimuth angle is excluded from the iterative process by using derived relations between the multicomponent measurements.

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.

The present invention improves measurement of the formation induction response in the presence of the primary magnetic field generated by a logging tool's transmitter. In a exemplary embodiment of the present invention, a structure is provided having a new combination of electrical and mechanical design features which provide logging tool for internal calibration and checking of antenna performance and characteristics before during and after well logging operations. In one aspect of the invention a logging tool is provided comprising a verification winding for coupling a verification signal into the receiver coil.

An induction logging tool is used on a MWD bottom hole assembly. Due to the finite, nonzero, conductivity of the mandrel, conventional multi frequency focusing (MFF) does not work. A correction is made to the induction logging data to give measurements simulating a perfectly conducting mandrel. MFF can then be applied to the corrected data to give formation resistivities.

A transverse induction logging tool having a transmitter and receiver for downhole sampling of formation properties, the tool having a symmetrical shielded split-coil transmitter coil and a bucking coil interposed between the split transmitter coils to reduce coupling of the transmitter time varying magnetic field into the receiver. The tool provides symmetrical shielding of the coils and grounding at either the transmitter or receiver end only to reduce coupling of induced currents into the received signal. The tool provides an insulator between receiver electronics and the conductive receiver housing having contact with conductive wellbore fluid, to reduce parasitic current flowing in a loop formed by the upper housing, feed through pipe, lower housing and wellbore fluid adjacent the probe housing or mandrel. An internal verification loop is provided to track changes in transmitter current in the real and quadrature component of the received data signal. A galvanic electrode is housed in the same mandrel with the induction logging receiver and transmitter.

The invention relates to an array induction logging coil system for measuring the formation resistivity. The coil system consists of a transmitting coil and 7 sets of double-receiving coils which consist of a plurality of screening coils and a plurality of main receiving coils, wherein the transmitting coil and each set of the double-receiving coils form a sub array, all 15 coils are wound on a non-conductive frame, the screening coils are connected with the main receiving coils in series, however, the winding directions of the screening coils and the main receiving coils are opposite, the set of the position of the main receiving coils considers the radial investigation depth, the lengthways resolution ratio and the signal focusing and synthesizing treatment requirement, the screening coils are arranged between the transmitting coil and the main receiving coils, the position and the number of the screening coils meet the condition of offsetting direct coupled signals, change the radial investigation depth and the lengthways resolution ratio, and meet the condition that the signal to noise ratio is 2-4; the other screening coils except the first sub array coil in the 7 sub array coils are overlapped with the center positions of the main receiving coils of the former sub array; and the investigation range of the resistivity is wide, so that the coil system can measure the formation resistivity more accurately.

An induction logging tool having transmitter and receiver antennas is used to make measurements of earth formations. The antennas may be mounted on the mandrel of a bottomhole assembly for MWD applications, or may be pad mounted for wireline applications. The induction measurements are inverted using a linearized model. The model parameters are determined in part from caliper measurements.

Measurements made by a cross-dipole acoustic logging tool in a borehole are processed to determine the principal directions of azimuthal anisotropy of a subsurface formation. Measurements indicative of azimuthal resistivity variations are also made with a multicomponent induction logging tool. These electrical measurements are processed using the principal direction determined from acoustic measurements to give an estimate of azimuthal resistivity variations. Based on modeling results, azimuthal resistivity variations are interpreted to estimate a fracture depth in the rock for known fluids therein.

The invention discloses a method for inverting stratum parameters by array induction logging data, which comprises the following steps of: obtaining array induction logging data and auxiliary logging curve data; layering a measured well section according to the array induction logging data and the auxiliary logging curve data, preliminarily inverting an array induction logging curve by a geometric factor method, and generating the initial original state stratum resistivity, the invaded zone resistivity and the invaded radius value of a corresponding layer; generating an array induction simulation response curve according to the initial original state stratum resistivity, the initial invaded zone resistivity and the initial invaded radius value of the corresponding layer; and judging whether the array induction simulation response curve is accordant with an array induction original response curve or not, if not, modifying the initial original state stratum resistivity, the invaded zone resistivity and the invaded radius value through the interactive inversion in combination with the geological characteristics of the corresponding layer according to the array induction original response curve, and outputting the final original state stratum resistivity, the final invaded zone resistivity and the final invaded radius value.

A method is disclosed for real-time (well-site) resistivity anisotropy determination using array lateral logs or any other unfocused, lateral-type measurements, and array induction logs or any other focused, induction-type measurements. Near-vertical wells with a deviation angle of less than 30 degrees are considered. Since with a lateral log, at each logging depth the injected current has both horizontal and vertical components, the data contains information related to both horizontal (R_h) and vertical (R_v) resistivities. With array induction tool, the induced current in near-vertical wells has only a horizontal component, and the induction data contain information related to R_h only. Having those two data sets acquired in the same well, it is possible to instantly estimate the formation resistivity anisotropy using square of a ratio between borehole and invasion corrected lateral and induction focused logs.

An antenna assembly for an induction logging tool for use in a drilling operation. The assembly includes an outer pressure housing, a coil former within the pressure housing, magnetic cores mounted in the housing, a core carrier within the coil former and the pressure housing which carries the magnetic cores, and shock-absorbing mountings on the core carrier for the magnetic cores.

The invention relates to a transient measurement method for the barefoot well formation resistivity. An emitting coil and a receiving coil of an induction logging instrument are coaxially placed in a formation; the emitting coil is controlled by a high power transistor in a full bridge converter, high-power and low-frequency bipolar rectangular waveforms are generated on the emitting coil, trigger signals trigger a receiving circuit at the moments of current disconnection and current connection, and transient voltage response waveforms inducted by the receiving coil are recorded; scale operation is conducted on transient response waveforms received by the tested formation and a set of received signals of a standard formation, and only a secondary field for reflecting the resistivity difference ratio of the tested formation is left; and the resistivity of the tested formation is obtained from response waveforms of the secondary field. According to the transient measurement method, the application range of a transient electromagnetic method to logging is widened, the method can be complementary to a common induction logging method, and obtained resistivity logging data can be used for formation evaluation and reservoir stratum division in the logging interpreting process, and also can be used for calculating the porosity, the saturability, the permeability and other parameters of reservoir stratums.

A multicomponent induction logging tool is used on a MWD bottomhole assembly. Multifrequency focusing that accounts for the finite, nonzero, conductivity of the mandrel is applied. Using separation of modes, the principal components and a direction of a conductivity tensor are determined. The results are used for reservoir navigation in earth formations. 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. 37 CFR 1.72(b)

In a multicomponent logging tool, a coil is electrically isolated by open circuiting another, substantially orthogonal coil.