Schlumberger Technology Corporation

Services Petroliers Schlumberger

Schlumberger Holdings Limited

Alexandre Abellan

Emmanuel Legendre

Martin G Luling

Fabienne Legendre

Henri Budan

Sofiane Ellouz

Mathieu Tarrius

Carlos Jeronimo Maeso

A method can include acquiring data from a borehole imaging tool disposed in a borehole in a formation where the borehole includes electrically insulating oil-based fluid introduced into the borehole as a drilling lubricant; determining, based on the data, electrically insulating oil-based fluid impeditivity and a reference formation impeditivity via a circuit model that includes series and parallel terms; and detecting a location of a fracture in the formation based on a change in current flow from the tool through the electrically insulating oil-based fluid and into the formation by determining an effective formation impeditivity based on at least a portion of the data for the location and by comparing the effective formation impeditivity to the reference formation impeditivity.

Fracture characterization while drilling

A method and apparatus to calibrate a resistivity measurement taken by a downhole tool in a borehole, wherein the downhole tool estimates the resistivity of an underground formation penetrated by the borehole with at least one sensor situated at a non-zero standoff distance from the borehole, is provided. The method includes taking apparent impedance measurements with the sensor at a set of frequencies and at a first plurality of locations in the borehole, wherein the measurement are uncalibrated measurements. The method also includes identifying a portion of the borehole in which the apparent impedance measurements at least at a first frequency of the set have a predetermined behavior. The predetermined behavior is that the apparent impedance measurements taken in the portion are substantially fitting a linear model when represented in the complex plane. The method also includes using a plurality of measurements obtained at a second plurality of location situated in said portion at the first frequency to determine calibration coefficients for the measurements at said frequency.

Method to automatically calibrate a downhole tool in an oil-based mud environment

A method includes emitting, with one or more sensors of a downhole tool disposed in a borehole, an excitation signal. The method also includes detecting, with the one or more sensors, a returned signal resulting from an interaction of the excitation signal with the borehole. The method further includes estimating a noise of the returned signal. The method also includes quantifying a probability that the estimated noise is not a white noise of the borehole. The method further includes identifying drill cuttings in a predetermined location of the borehole based on said quantification.

Downhole detection of cuttings

Apparatus and methods operable to determine between a wall of a wellbore penetrating in a subterranean formation and a resistivity tool disposed in the wellbore. One such method includes using an apparent impedance function depending on a frequency variable and a plurality of unknown parameters, at least one of the unknown parameters depending on a formation impedance of the subterranean formation. The method also includes applying a voltage, at each of a plurality of frequency values, between electrodes of a resistivity tool that is disposed in the wellbore. The method also includes measuring, across the electrodes, a plurality of apparent impedance values, each corresponding to a different one of the frequency values. The method still further includes determining the unknown parameters based on the frequency values and the apparent impedance values, and estimating the standoff distance based on an expression that includes at least one of the unknown parameters.

Determining standoff between a wall of a wellbore and a tool disposed in the wellbore

Apparatus and methods operable to determine a resistivity of a subterranean formation surrounding a wellbore. One such method includes using an apparent impedance function depending on a frequency variable and a plurality of unknown parameters, at least one of the unknown parameters depending on a formation impedance of the subterranean formation. The method also includes applying a voltage, at each of a plurality of frequency values, between electrodes of a resistivity tool that is disposed in the wellbore. The method also includes measuring, across the electrodes, a plurality of apparent impedance values, each corresponding to a different one of the frequency values. The method still further includes determining the unknown parameters based on the frequency values and the apparent impedance values, and estimating the formation resistivity based on an expression that includes at least one of the unknown parameters.

Method and apparatus for determining resistivity of a formation

The present disclosure introduces an apparatus for downhole measurement of a formation resistivity. The apparatus includes a probe having a button electrode, a first guard electrode insulated from the button electrode, a second guard electrode insulated from the first guard electrode, and a return electrode positioned external to the second guard electrode. The apparatus also includes an electrical source for setting a voltage drop between the second guard electrode and the return electrode, a first impedance (R) electrically coupled between the button electrode and the second guard electrode, and a second impedance (R) electrically coupled between the first guard electrode and the second guard electrode.

Growing community of inventors

Clamart, France

Alexandre Abellan