Geo-steering using electromagnetic gap impedance data

Patent metadata

Field	Value
Publication number	US-11719048-B2
Application number	US-202017060498-A
Country	US
Kind code	B2
Filing date	Oct 1, 2020
Priority date	Oct 1, 2019
Publication date	Aug 8, 2023
Grant date	Aug 8, 2023

Abstract

A method for steering a downhole tool includes receiving an electromagnetic (EM) signal from the downhole tool. The downhole tool is in a wellbore in a formation. The EM signal comprises a gap voltage and a gap current that are measured across a gap sub in the downhole tool. The method also includes determining a gap impedance based at least partially upon the gap voltage and the gap current. The method also includes determining a first formation resistivity at a first location in the wellbore based at least partially upon the gap impedance. The method also includes steering the downhole tool based at least partially upon the first formation resistivity.

First claim

What is claimed is:

1. A method for steering a downhole tool, comprising:
receiving a first electromagnetic (EM) signal from the downhole tool, wherein the downhole tool is in a wellbore in a formation, and wherein the first EM signal comprises first measurement data obtained by the downhole tool;
receiving a second EM signal from the downhole tool a predetermined duration after receiving the first EM signal, wherein the second EM signal comprises second measurement data comprising a gap voltage and a gap current that are measured across a gap sub in the downhole tool when the first EM signal is transmitted from the downhole tool at a first location in the wellbore;
determining a gap impedance based at least partially upon the gap voltage and the gap current of the second measurement data;
determining a first formation resistivity at the first location in the wellbore based at least partially upon the gap impedance of the second measurement data and a trained neural network comprising a library of gap impedance data measured in one or more other wellbores in the formation; and
steering the downhole tool based at least partially upon the first formation resistivity, wherein steering comprises varying an inclination angle of the downhole tool, the azimuthal angle of the downhole tool, or both.

2. The method of claim 1 , wherein determining the first formation resistivity comprises comparing the gap impedance of the second measurement data to gap impedance data in a library.

3. The method of claim 2 , wherein the library also comprises formation resistivity data corresponding to the gap impedance data, and wherein the formation resistivity data is estimated in the one or more other wellbores in the formation.

4. The method of claim 1 , comprising:
receiving a third EM signal from the downhole tool after receiving the second EM signal, wherein the third EM signal comprises third measurement data comprising a second gap voltage and a second gap current that are measured across the gap sub in the downhole tool when the second EM signal is transmitted from the downhole tool at the second location in the wellbore;
determining a second gap impedance based at least partially upon the second gap voltage and the second gap current of the third measurement data;
determining a second formation resistivity at the second location in the wellbore based at least partially upon the second gap impedance; and
determining a difference between the first formation resistivity and the second formation resistivity, wherein the difference indicates a boundary between a first layer of the formation at the first location and a second layer of the formation at the second location, wherein the boundary is between the gap sub and a drill bit of the downhole tool.

5. The method of claim 4 , comprising:
receiving a fourth EM signal from the downhole tool after receiving the third EM signal, wherein the fourth EM signal comprises fourth measurement data comprising a third gap voltage and a third gap current that are measured across the gap sub in the downhole tool when the third EM signal is transmitted from the downhole tool at the third location in the wellbore;
determining a third gap impedance based at least partially upon the third gap voltage and the third gap current of the fourth measurement data;
determining a third formation resistivity at the third location in the wellbore based at least partially upon the third gap impedance; and
determining a second difference between the second formation resistivity and the third formation resistivity, wherein the second difference indicates a second boundary between the second layer of the formation at the second location and a third layer of the formation at the third location, wherein the second boundary is between the gap sub and the drill bit of the downhole tool.

6. The method of claim 1 , wherein the first formation resistivity is determined based at least partially upon a vertical sensitivity of the gap impedance, and wherein the vertical sensitivity of the gap impedance is greater when a distance between the gap sub and a drill bit of the downhole tool is greater than a thickness of a layer of the formation in which the downhole tool is positioned than when the distance between the gap sub and the drill bit is less than the thickness of the layer of the formation in which the downhole tool is positioned.

7. The method of claim 1 , wherein the gap impedance is determined based at least partially upon a resistivity contrast of a fluid in the wellbore.

8. The method of claim 1 , further comprising determining a type of fluid in the wellbore proximate to the downhole tool, wherein the first formation resistivity is also determined based at least partially upon the type of the fluid.

9. The method of claim 1 , further comprising:
receiving a third EM signal from the downhole tool after receiving the second EM signal, wherein the third EM signal comprises third measurement data comprising a second gap voltage and a second gap current that are measured across the gap sub in the downhole tool when the second EM signal is transmitted from the downhole tool at the second location in the wellbore;
determining a second gap impedance based at least partially upon the second gap voltage and the second gap current of the third measurement data;
determining a second formation resistivity at the second location in the wellbore; and
determining a difference between the first formation resistivity and the second formation resistivity, wherein the difference indicates a boundary between a first layer of the formation and a second layer of the formation, and wherein steering the downhole tool comprises steering a drill bit of the downhole tool to remain within the first layer of the formation.

10. The method of claim 1 , further comprising:
receiving a third EM signal from the downhole tool after receiving the second EM signal, wherein the third EM signal comprises third measurement data comprising a second gap voltage and a second gap current that are measured across the gap sub in the downhole tool when the second EM signal is transmitted from the downhole tool at the second location in the wellbore;
determining a second gap impedance based at least partially upon the second gap voltage and the second gap current of the third measurement data;

determining a second formation resistivity at the second location in the wellbore; and
determining a difference between the first formation resistivity and the second formation resistivity, wherein the difference indicates a boundary between a first layer of the formation and a second layer of the formation, and wherein steering the downhole tool comprises steering a drill bit of the downhole tool to enter the second layer of the formation.

11. A method for steering a drill bit of a downhole tool, comprising:
transmitting a first electromagnetic (EM) signal from the downhole tool to a computing system at the surface, wherein the downhole tool is in a wellbore in a formation and the first EM signal comprises first measurement data obtained by the downhole tool;
measuring a gap voltage across a gap sub in the downhole tool while the first EM signal is being transmitted, wherein the gap voltage is generated by transmitting the first EM signal;
measuring a gap current across the gap sub in the downhole tool while the first EM signal is being transmitted, wherein the gap current is generated by transmitting the first EM signal;
transmitting a second EM signal from the downhole tool to the computing system after a predetermined duration less than 5 minutes from transmitting the first EM signal, wherein the second EM signal comprises

Assignees

• Schlumberger Technology Corp

Inventors

• Depavia Luis Eduardo
• Chen Jiuping
• Sun Liang
• Hunter Richard

Classifications

• E21B7/04 Primary

  Directional drilling · CPC title

• E21B7/068

  drilled by a down-hole drilling motor (down-hole drives per se E21B4/00, E21B7/067 takes precedence) · CPC title

• E21B7/10

  Correction of deflected boreholes · CPC title

• E21B47/0228

  using electromagnetic energy or detectors therefor · CPC title

• E21B47/13

  by electromagnetic energy, e.g. radio frequency · CPC title