Schlumberger Technology Corporation

Services Petroliers Schlumberger

Schlumberger Holdings Limited

Prad Research and Development Limited

Andrew J Hayman

Philip S Cheung

Richard Bloemenkamp

Dennis J Pittman

Tarek M Habashy

Dzevat Omeragic

Benoit G Froelich

Thilo Michael Brill

Jean-Luc Le Calvez

Yong-Hua Chen

Christoph Klieber

Thomas Barrou

Kenneth K Liang

Laetitia Comparon

Abdurrahman Sezginer

Gregoire Max Jacob

Christopher V Kimball

Gaelle Jannin

Sylvain Thierry

Fred E Stanke

Patrick P Vessereau

Curtis J Randall

Olivier Faivre

Charles Durbec

Grégoire Jacob

Systems and methods are provided for obtaining a flexural-attenuation measurement for cement evaluation that may be effective even for wells with relatively thick casings. A method includes emitting an acoustic signal at a casing in a well that excites the casing into generating an acoustic response signal containing acoustic waves, such as Lamb waves. The Lamb waves include flexural waves and extensional waves. The casing may be relatively large, having a thickness of at least 16 mm. The acoustic response signal may be detected and filtered to reduce a relative contribution of the extensional waves. This may correspondingly increase a relative contribution of the flexural waves. The filtered acoustic response signal may be used as a flexural-attenuation measurement for cement evaluation.

Flexural wave measurement for thick casings

A system includes an acoustic logging tool including a transducer configured to: emit a first acoustic pulse in a first direction toward a first acoustic surface; measure a first acoustic signal, wherein the first acoustic signal includes a coherent noise component and a first echo component, wherein the first echo component is due at least in part to an interaction of the first acoustic pulse with the first acoustic surface; emit a second acoustic pulse in a second direction, wherein the second direction is at least partly directed away from the first acoustic surface; and measure a second acoustic signal, wherein the second acoustic signal includes substantially only the coherent noise component. The system also includes a data processing system that includes a processor configured to remove the measurement of the second acoustic signal from the measurement of the first acoustic signal to reduce coherent noise.

Coherent noise estimation and reduction for acoustic downhole measurements

System and methods of generating calibrated downhole images of a subterranean formation () surrounding a wellbore (). The method involves placing a pad at a distance from a highly conductive surface and measuring a current between return electrodes of the pad and the highly conductive surface. The current may be used to determine a theoretic impedance of the current path, and impedance amplitude and impedance phase may be calibrated using theoretical impedance phase and theoretical impedance amplitude. Multiple standoff calibrations and temperature variation calibrations may also be used.

Method and system for calibrating a downhole imaging tool

Methods and devices for obtaining well log data with reduced coherent noise are provided. One such method may include placing a downhole tool into a well to obtain a set of unfiltered well log data that includes individual measurements obtained at various azimuthal angles within the well. Some of the unfiltered well log data may represent eccentered well log data obtained while the downhole tool is eccentered in the well. The individual measurements of the eccentered well log data may have delays that vary as a function of the azimuthal angle at which they were obtained. By comparing the measurements of the eccentered well log data, a common pattern independent of delay, representing coherent noise, may be identified. The common pattern may be subtracted from the well log data to produce filtered well log data that is less noisy than the unfiltered well log data.

Systems and methods for removing coherent noise in log data

System and methods of generating calibrated downhole images of a subterranean formation () surrounding a wellbore (). The method involves measuring open hole and cased hole measurements with a downhole tool (); determining () open hole parameters (e.g., Z90) from the cased hole parameters, known parameters and the open hole measurements; and generating () downhole outputs from the determined open hole parameters.

Surface equipment of a cement analysis system (CAS) estimates a first drilling fluid slowness (FSLO) and a first drilling fluid acoustic impedance (ZMUD) based on a type and density of wellbore drilling fluid. A second FSLO is estimated based on a thickness and diameter of wellbore casing and transit time for energy emitted by a downhole tool to travel to and from the casing. An FSLO graphical interface is generated based on the first and second FSLO. A second ZMUD is estimated based on the drilling fluid type and density and one of the first and second FSLO selected utilizing the FSLO graphical interface. A ZMUD graphical interface is generated based on the first and second ZMUD. The downhole tool then obtains log data utilizing at least one parameter selected utilizing the ZMUD graphical interface. The log data includes a final ZMUD measured with respect to wellbore depth.

Cement evaluation

Systems, tools and techniques for measuring downhole parameters are provided. The techniques involve providing a downhole tool with a sensing apparatus. The sensing apparatus has at least one source positionable about the downhole tool, at least one sensor electrode positionable about a front face of the downhole tool for measuring electrical signals from the source, and a raised insulating cover positionable along the front face of the downhole tool for defining at least one contact surface. The raised insulating cover extends over at least a portion of the sensor electrode whereby the sensor electrode is positionable adjacent to the subterranean formation for electrically coupling thereto without direct contact therewith.

System and method for measuring downhole parameters

A system and method for imaging properties of subterranean formations in a wellbore is provided. The system comprises a formation sensor for collecting currents injected into the subterranean formations, the formation sensor positionable on a downhole tool deployable into the wellbore. The system comprises a controller for controlling the formation sensor and a formation imaging unit. The formation imaging unit comprises a current management unit for collecting data from the currents injected into the subterranean formations, the currents having at least two different frequencies. The formation imaging unit comprises a drilling mud data unit for determining at least one drilling mud parameter, a formation data unit for determining at least one formation parameter from the collected data, and an inversion unit for determining at least one formation property by inverting the at least one formation parameter.

System and method for imaging properties of subterranean formations

The disclosure is concerned with a tool and method for imaging a formation through a substantially non-conductive medium. The tool includes one or more injection electrodes for injecting current through the substantially non-conductive medium and into the formation. The tool further includes one or more return electrodes for receiving current from the substantially non-conductive medium, the formation, or both. The tool also includes circuitry for determining a complex impedance based on the received current, determining a phase angle of the complex impedance, and determining a component of the complex impedance that is orthogonal to the phase angle.

Tool for imaging a downhole environment

An acoustic logging tool emits a wideband acoustic pulse toward an inside surface of a borehole casing and an acoustic response is received. The acoustic response is analyzed at one or more higher order harmonics of the thickness mode resonance of the casing to determine the acoustic impedance of the material behind the casing.

Using higher order harmonics to determine acoustic impedance of material behind borehole casings

The present disclosure provides an apparatus and method for measuring electrical properties of an underground formation surrounding a borehole. The apparatus preferably comprises a downhole tool positionable in the borehole, a sensor pad positionable on the downhole tool, and a plurality of electrodes mounted on the sensor pad and configured to face a wall of the borehole. The apparatus further comprises an insulating layer extending over at least a portion of the plurality of electrodes facing the wall of the borehole.

Apparatus and method for measuring electrical properties of an underground formation

The invention is concerned with a tool and method for determining standoff from a formation though mud. The tool comprising a first electrode located at a distance from the formation for measuring a first impedance. A second electrode is located at a second distance from the formation for measuring a second impedance. A processing unit measures a difference between the first impedance and the second impedance, uses the difference to determine a conductivity of the mud and based thereon, determines the standoff of at least one of the first and the second electrode.

The invention is concerned with a tool for imaging a formation, the tool comprising: a pad capable of alignment adjacent a wall of the formation. The pad has located thereon an imaging electrode for injecting current into the formation. There is a first return electrode separated from the imaging electrode for receiving the injected current. There is at least one recessed electrode that is located at a different distance from the wall of the formation as the other electrodes.

Apparatus for making measurements in boreholes comprising a sonde having a radial array of arms provided thereon; wherein the sonde is connectable to a cartridge containing electronic circuitry specific to a predetermined measurement to be made in the borehole, each arm is connectable to a sensor pad specific to the predetermined measurement; and the sonde provides electrical connectivity between the sensor pads and the cartridge that is substantially independent of the predetermined measurement.

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Voisins-le-Bretonne, France

Andrew J Hayman