Abstract: An artificial neural network, ANN, and method of training the ANN for inversion of logging tool signals into well logs of formation parameters is disclosed. Properly selected synthetic models of earth formations are used to train the ANN. The models include Oklahoma and chirp type of formations. In each model parameter contrasts of from 10 to 1 to about 100 to 1 are included. Models including maximum and minimum parameter values spanning the operating range of the selected logging tool are included. Parameter contrasts at interfaces are limited to realistic values found in earth formations. The selected models are used to generate synthetic tool signals, which are then used as inputs to the ANN for training. When the ANN coefficients are properly adjusted to produce an output matching the original models, the ANN can be used for inversion of any real signals from the selected logging tool.

Abstract: An artificial neural network, ANN, and method of training the ANN for inversion of logging tool signals into well logs of formation parameters is disclosed. Properly selected synthetic models of earth formations are used to train the ANN. The models include Oklahoma and chirp type of formations. In each model parameter contrasts of from 10 to 1 to about 100 to 1 are included. Models including maximum and minimum parameter values spanning the operating range of the selected logging tool are included. Parameter contrasts at interfaces are limited to realistic values found in earth formations. The selected models are used to generate synthetic tool signals, which are then used as inputs to the ANN for training. When the ANN coefficients are properly adjusted to produce an output matching the original models, the ANN can be used for inversion of any real signals from the selected logging tool.

Abstract: A coil arrangement and method of collecting and processing data in induction logging of wells is disclosed. The coil arrangement includes three essentially identical coils made of elliptical conductive loops lying in a plane tilted from the axis of the logging tool. Each coil is centered on the same point in space. Data are preferably collected by using the coil arrangement for both transmitter and receiver, and transmitting at three closely-spaced frequencies, one from each of the transmitter coils. The transmitted signals are received and recorded, at which time they are operated on mathematically to create rotation of an after-the-fact virtual sonde for measuring desired earth formation properties.

Abstract: A coil arrangement and method of collecting and processing data in induction logging of wells is disclosed. The coil arrangement includes three essentially identical coils made of elliptical conductive loops lying in a plane tilted from the axis of the logging tool. Each coil is centered on the same point in space. Data are preferably collected by using the coil arrangement for both transmitter and receiver, and transmitting at three closely-spaced frequencies, one from each of the transmitter coils. The transmitted signals are received and recorded, at which time they are operated on mathematically to create rotation of an after-the-fact virtual sonde for measuring desired earth formation properties.

Abstract: A well logging system is disclosed having an improved speed correction apparatus and method. One embodiment comprises a logging sonde, a wireline cable, a distance sensor, a tension sensor, and a surface computer. The logging sonde moves through a wellbore while making logging measurements of the formation around the wellbore. The sonde includes an accelerometer to measure acceleration of the logging sonde. As the wireline cable is reeled in on the surface, the distance sensor detects the length of wireline cable that is retrieved. The tension sensor measures the tension in the wireline cable. The surface computer receives measurements from the accelerometer, the distance sensor, and the tension sensor, and determines intervals in which the logging tool is stuck. At least in part, this is done by finding “slow” intervals in which the wireline cable is stretching at about the same rate that the wireline cable is being reeled in.

Abstract: A coil array for high resolution induction logging comprises a transmitter, a first receiver set positioned at a first distance from the transmitter and a second receiver set positioned at a second distance from the transmitter, and the second receiver set includes at least one portion of the first receiver set. Also disclosed is a method for deriving an apparent conductivity log from at least one induction well log that comprises a plurality of depth samples, comprising the steps of raising each depth sample of the apparent conductivity signal to several predetermined powers to generate a plurality of powers of conductivity, convolving in depth the powers of conductivity with a plurality of filters, where each power has a distinct filter, and summing the results of all of the convolutions to produce a conductivity log that is substantially free from the effects of adjacent beds and the nonlinear effects of true conductivity.

Abstract: A coil array for high resolution induction logging comprises a transmitter, a first receiver set and a second receiver set. The second receiver set includes at least one portion of the first receiver set. A method for deriving an apparent conductivity log from at least one induction well log that comprises a plurality of depth samples comprises raising each depth sample to several predetermined powers, convolving in depth the powers of conductivity, and summing the convolutions to produce a conductivity log. An apparatus for measuring the resistivity of an earth formation, comprises a transmitter energized by a time-varying, periodic voltage, a set of receivers generating a receiver voltage, an analog-to-digital converter that outputs a digitized voltage signal, and a processor that receives the digitized voltage signal.

Abstract: A coil array for high resolution induction logging comprises a transmitter, a first receiver set and a second receiver set. The second receiver set includes at least one portion of the first receiver set. A method for deriving an apparent conductivity log from at least one induction well log that comprises a plurality of depth samples, comprises raising each depth sample to several predetermined powers, convolving in depth the powers of conductivity, and summing the convolutions to produce a conductivity log. An apparatus for measuring the resistivity of an earth formation, comprises a transmitter energized by a time-varying, periodic voltage, a set of receivers generating a receiver voltage, an analog-to-digital converter that outputs a digitized voltage signal, and a processor that receives the digitized voltage signal.

Abstract: A coil array for high resolution induction logging comprises a transmitter, a first receiver set positioned at a first distance from the transmitter and a second receiver set positioned at a second distance from the transmitter, and the second receiver set includes at least one portion of the first receiver set. Also disclosed is a method for deriving an apparent conductivity log from at least one induction well log that comprises a plurality of depth samples, comprising the steps of raising each depth sample of the apparent conductivity signal to several predetermined powers to generate a plurality of powers of conductivity, convolving in depth the powers of conductivity with a plurality of filters, where each power has a distinct filter, and summing the results of all of the convolutions to produce a conductivity log that is substantially free from the effects of adjacent beds and the nonlinear effects of true conductivity.

Abstract: A coil array for high resolution induction logging comprises a transmitter, a first receiver set positioned at a first distance from the transmitter and a second receiver set positioned at a second distance from the transmitter, and the second receiver set includes at least one portion of the first receiver set. Also disclosed is a method for deriving an apparent conductivity log from at least one induction well log that comprises a plurality of depth samples, comprising the steps of raising each depth sample of the apparent conductivity signal to several predetermined powers to generate a plurality of powers of conductivity, convolving in depth the powers of conductivity with a plurality of filters, where each power has a distinct filter, and summing the results of all of the convolutions to produce a conductivity log that is substantially free from the effects of adjacent beds and the nonlinear effects of true conductivity.

Abstract: A well logging system is disclosed having an improved speed correction apparatus and method. One embodiment comprises a logging sonde, a wireline cable, a distance sensor, a tension sensor, and a surface computer. The logging sonde moves through a wellbore while making logging measurements of the formation around the wellbore. The sonde includes an accelerometer to measure acceleration of the logging sonde. As the wireline cable is reeled in on the surface, the distance sensor detects the length of wireline cable that is retrieved. The tension sensor measures the tension in the wireline cable. The surface computer receives measurements from the accelerometer, the distance sensor, and the tension sensor, and determines intervals in which the logging tool is stuck. At least in part, this is done by finding “slow” intervals in which the wireline cable is stretching at about the same rate that the wireline cable is being reeled in.

Abstract: A system and method for performing inversion and for correcting for shoulder bed effect. The method enhances the resolution of wave propagation resistivity logs and corrects the logs for adjacent bed effects, whereby the resulting logs have a vertical response as good as wireline high-resolution induction logs. The method first performs logging while drilling on a formation to obtain LWD resistivity log data. The method then selects one or more control depths at one or more locations of each of a plurality of detected beds in the formation. The present invention includes a novel method for selecting bed boundaries from the log data, and the control depths are then determined based on the determined bed boundaries. The method then estimates the resistivity of each bed only at the selected control depths to produce an estimated resistivity of the beds. The method then computes a simulated log value at each control depth using a current estimate of the resistivity of the beds.

Abstract: An improved induction well logging processing technique for determining conductivity measurements of subsurface earth strata. An in-phase conductivity signal and a quadrature conductivity signal are obtained from a downhole induction logging tool. The in-phase conductivity signal and the cubed square root of the in-phase conductivity signal are filtered by a first filter and a second filter, respectively. The outputs of the filters may be summed to provide a first conductivity signal having reduced environmental effects and indicating the conductivity of the earth formation under test. Additionally, the in-phase conductivity signal and the quadrature signal may be filtered and summed to provide a second conductivity signal. A weighted average of the first and second conductivity signals may be used as an indication of the earth formation conductivity.

Abstract: An induction tool including a coil array having a plurality of transmitter coils and a plurality of receiver coils. Each plurality of coils is symmetrically arranged on an insulated mandrel about a selected point. The induction tool also includes an oscillator circuit that provides an alternating frequency signal to the transmitter coils. A receiver circuit is connected to the receiver coils to measure signals indicative of the voltages induced on these receiver coils to the surface. By varying the spacing between the receiver coils and transmitter coils it is possible to independently vary the vertical and radial measurement capabilities of the tool of the present invention. A dual induction tool having high vertical resolution is also disclosed. The dual induction tool includes a pair of transmitter/receiver coil arrays, each transmitter/receiver coil array having a different transmitter-to-receiver coil spacing and substantially indentical vertical resolution.

Abstract: A floatable magnetic filter screen (10, 40, 52, 60) for removing metallic debris from work-functioning baths (26, 26') comprises a tubular rectangular outer frame (11, 11', 14, 14', 16, 61) that supports a plurality of magnet-forming webs (18, 18', 62), in a predetermined array, within the central opening thereof. The magnets (23, 23', 64) of each web, when required, are encapsulated within a protective material covering (e.g., 19, 19') so as to physically isolate them from a given bath (26, 26') within which the filter screen (10, 40, 52, 60) is to be employed. While the filter screen is adapted to normally float on the surface of a given bath, through piece part (33, 33', 53) initiated immersion of the filter screen in the bath, preferably using a piece part-carrying basket (36, 36', 51), the bath solution is effectively forced through the filter screen during both the downward and subsequent upward displacement of the latter.