Schlumberger Technology Corporation

Schlumberger Canada Limited

Services Petroliers Schlumberger

Schlumberger Holdings Limited

Prad Research and Development Limited

David L. Smith

Mark T. Frey

Mark T Frey

Brian Oliver Clark

Dean M Homan

David L Smith

Anthony Louis Collins

Dhananjay Ramaswamy

Stephen D Bonner

John F Hunka

Peter T Wu

James Stephen Hall

Mark A Fredette

Dominique Dion

Dzevat Omeragic

Jacques R Tabanou

Helen Xiaoyan Zhong

Richard A Rosthal

Qiming Li

Keith A Moriarty

Michael H Du

Jan Smits

Robert J Utter

Anatoly Dementyev

Weixin Dong

Steve F Crary

Christophe Dupuis

Devin Rock

Sergiy Kryukov

Ettore Mirto

Paul Bertrand

Rachel Belleville

Patrick Fisseler

Martin G Lüling

Luc Argentier

Martin G L&uuml;ling

A shield for deployment about an antenna on an electromagnetic logging tool includes an electrically conductive, hollow body configured for coaxial deployment about the antenna. The hollow body includes a plurality of slots that extend through the hollow body. An outer surface of the hollow body includes at least one recess, at least a portion of which extends between and substantially orthogonal to the plurality of slots.

Antenna shield for electromagnetic logging tool

An integrated drilling system includes a rotary steerable control unit and an electromagnetic LWD control unit deployed in an external collar. The rotary steerable control unit is deployed below the electromagnetic LWD control unit and is configured to control a direction of drilling of the integrated drilling system. A near bit electromagnetic antenna is deployed in a recess on the collar circumferentially about the rotary steerable control unit. At least one electromagnetic transmitter and at least one electromagnetic receiver are deployed in corresponding recesses in the collar circumferentially about the electromagnetic LWD control unit with the at least one transmitter and at least one receiver configured to make electromagnetic logging measurements while drilling. An electrical jumper provides an electrical connection between the near bit electromagnetic antenna and the electromagnetic LWD control unit.

Integrated drilling system

A method for making calibrated directional electromagnetic logging measurements includes causing an electromagnetic logging tool to make a plurality of voltage measurements while deployed in a subterranean wellbore. A ratio of currents in first and second electromagnetic transmitters is computed and a ratio of gains in first and second electromagnetic receivers is computed. A ratio of selected ones of the measured voltages is processed in combination with the ratio of currents, the ratio of gains, and a test loop calibration coefficient to compute the calibrated directional electromagnetic logging measurement.

Directional electromagnetic ratio calibration

Methods capable of determining a depth of investigation of a logging tool can include generating an error distribution model for a logging tool. The methods can also include defining a detection threshold above which a measured signal from a measurement channel of the logging tool can be considered reliable based on output from the error distribution model, and generating a simulated formation model to determine the depth of investigation. The depth of investigation can be biased by the detection threshold.

Methods and systems to analyze bed boundary detection

A calibration method includes determining calibration standards for a reference tool including a reference transmitter and a reference receiver. First and second calibration factors are measured to match a receiver on an electromagnetic measurement tool (the tool to be calibrated) to the reference receiver and to match a transmitter on the electromagnetic measurement tool to the reference transmitter. The electromagnetic measurement tool is deployed in a subterranean wellbore and used to make electromagnetic measurements therein. The measured first and second calibration factors and at least one of the calibration standards are applied to at least one of the electromagnetic measurements to compute a gain calibrated electromagnetic measurement.

Calibration of electromagnetic measurement tool

A method for making downhole electromagnetic logging measurements of a subterranean formation is disclosed. An electromagnetic logging tool is rotated in a subterranean wellbore. The tool includes a transmitter axially spaced apart from a receiver. The transmitter may include an axial transmitting antenna and at least one transverse transmitting antenna and the receiver may include an axial receiving antenna and at least one transverse receiving antenna. The transmitting antennas transmit corresponding electromagnetic waves into the subterranean wellbore. The receiving antennas receive corresponding voltage measurements which are processed to compute harmonic voltage coefficients. Ratios of the selected harmonic voltage coefficients are processed to compute gain compensated, azimuthally invariant measurement quantities.

Compensated azimuthally invariant electromagnetic logging measurements

A method for making gain compensated electromagnetic logging measurements of a subterranean formation includes rotating an electromagnetic logging tool in a subterranean wellbore. The logging tool includes a transmitter having at least one transmitting antenna axially spaced apart from a receiver having at least one receiving antenna. Electromagnetic waves are transmitted into the subterranean wellbore using the at least one transmitting antenna. Voltage measurements corresponding to the transmitted electromagnetic waves are received at the receiving antenna. The voltage measurements are processed to compute real and imaginary directional resistivity measurement quantities.

Real and imaginary components of electromagnetic logging measurements

A method for making downhole electromagnetic logging measurements includes using an electromagnetic measurement tool to acquire the measurements while rotating in a subterranean wellbore. Received electromagnetic waves are processed to obtain harmonic voltage coefficients, ratios of which are in turn further processed to compute gain compensated measurement quantities. The gain compensated measurement quantities are further processed to compute at least one of an apparent formation azimuth of the formation through which the wellbore traverses, an apparent tool eccentering azimuth, and an eccentering distance of the logging tool in the wellbore.

Method for estimating formation dip azimuth and eccentering azimuth

A logging tool having a plurality of spatially separated antennas is provided and used to make propagation-style measurements in a formation. Tensors are formed using the propagation-style measurements and one or more quantities are computed using the tensors. A formation evaluation is performed using the computed quantities. The formation evaluation determines a formation property or parameter such as horizontal resistivity, vertical resistivity, relative dip, azimuthal dip, bed boundary location, or bed thickness. The computed quantities may include compensated phase shift resistivity, compensated attenuation resistivity, symmetrized phase shift resistivity, symmetrized attenuation resistivity, anti-symmetrized phase shift resistivity, and anti-symmetrized attenuation resistivity. The measurements may be corrected for antenna gain errors and an air calibration may be performed. A zero-dimension inversion may be performed, while drilling, and the determined horizontal resistivity, vertical resistivity, relative dip, and/or azimuthal dip information may be sent to an uphole processor in real-time.

Formation properties from conductivity tensor

A method for making downhole electromagnetic logging while drilling measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The logging while drilling tool includes at least first and second tilted transmitter antennas longitudinally spaced along a logging while drilling tool body and at least first and second tilted receiver antennas. A plurality of electromagnetic voltage measurements is acquired at the first and second tilted receiver antennas while rotating and processed to compute harmonic voltage coefficient. Ratios of selected ones of the harmonic voltage coefficients are then processed to compute at least one gain compensated measurement quantity.

System and methods for obtaining compensated electromagnetic measurements

A method for obtaining gain compensated electromagnetic logging while drilling propagation measurements includes rotating an electromagnetic logging while drilling tool in a subterranean wellbore. The tool includes a plurality of transmitter antennas and a plurality of receiver antennas symmetrically spaced along a logging while drilling tool body with the transmitter antennas including at least one axial transmitter antenna and at least one transverse transmitter antenna and the receiver antennas including at least one axial receiver antenna and at least one transverse receiver antenna. Electromagnetic voltage measurements are acquired from the receiver antennas while rotating. The acquired voltage measurements are processed to compute harmonic voltage coefficients. Ratios of selected ones of the harmonic voltage coefficients are in turn processed to compute gain compensated quantities including symmetrized and anti-symmetrized quantities.

Gain compensated directional propagation measurements

An arrangement for generating a resistivity image having a drill bit with cutters configured to be placed within a wellbore, the cutters configured to create further sections of the wellbore upon rotation, the drill bit having an end with threads for engagement, at least one section of drill string connected to the drill bit through a matching set of threads for engagement, a receiver toroid connected to the at least one section of drill string along at least a portion of the drill string, a transmitter toroid connected to the at least one section of drill string and located at least a portion of the drill string away from the receiver toroid, at least one stabilizer connected to the at least one section of drill string, a power source connected to the transmitter toroid and the receiver toroid, an electrode arrangement placed at the drill bit, wherein the electrode arrangement is electrically connected to the drill bit through a non-linear circuit element and a computer arrangement connected to the receiver toroid.

Measuring current from an electrode using a non-linear element

A method for obtaining full tensor gain compensated propagation measurements includes processing a full tensor voltage measurement to obtain a fully gain compensated tensor quantity. An electromagnetic logging tool including at least first and second axially spaced transmitters and at least first and second axially spaced receivers is rotated in a subterranean borehole. A plurality of voltage measurements are acquired while rotating to obtain a full tensor voltage measurement which is in turn processed to obtain the fully gain compensated tensor quantity.

Full tensor gain compensated propagation measurements

Gain compensated tensor propagation measurements using collocated antennas

A method for obtaining gain corrected triaxial electromagnetic propagation measurements with an offset correction includes deploying an electromagnetic logging tool in a subterranean borehole. The logging tool includes at least first and second axially spaced triaxial transmitters and at least first and second axially spaced triaxial receivers. A plurality of full tensor voltage measurements may be acquired and processed tensor term by tensor term to obtain a full tensor, gain corrected quantity. The processing may optionally include (i) removing a full tensor voltage offset from the acquired full tensor voltage measurements to obtain a corresponding plurality of offset corrected voltage tensors and (ii) processing the offset corrected voltage tensor term by tensor term to obtain the full tensor, gain and offset corrected quantity.

Term by term gain calibration of triaxial propagation measurements

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Sugar Land, TX, United States of America

Mark T Frey