Modelling electromagnetic telemetry signals in deviated wells

Patent metadata

Field	Value
Publication number	US-10704385-B2
Application number	US-201916251120-A
Country	US
Kind code	B2
Filing date	Jan 18, 2019
Priority date	Jan 19, 2018
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

A method for modeling an electromagnetic (EM) telemetry signal includes straightening a well in a model and dividing the well into a plurality of segments. The method also includes determining an electrical current in one or more of the segments when the well is straightened. The method also includes replacing the well with equivalent electrical sources based at least partially upon the electrical current in one or more of the segments. The method also includes bending the well back into its original shape in the model and determining the electrical current in one or more of the segments by projection when the well is back in its original shape. The method also includes summing EM fields for each of the one or more segments to estimate the EM telemetry signal.

First claim

What is claimed is:

1. A method for modeling an electromagnetic (EM) telemetry signal, comprising:
straightening a well in a model;
dividing the well into a plurality of segments;
determining an electrical current in one or more of the plurality of segments when the well is straightened;
replacing the well with equivalent electrical sources based at least partially upon the electrical current in the one or more of the plurality of segments;
bending the well back into its original shape in the model;
determining an electrical current in the one or more of the plurality of segments by projection when the well is back in its original shape; and
summing EM fields for each of the one or more of the plurality of segments, based at least partially upon the electrical current in the one or more of the plurality of segments when the well is back in its original shape, to estimate the EM telemetry signal.

2. The method of claim 1 , wherein the well is substantially vertical when straightened.

3. The method of claim 1 , further comprising simulating the EM telemetry signal from a transmitter in the well, which generates the electrical current in the one or more of the plurality of segments when the well is straightened.

4. The method of claim 1 , wherein the equivalent electrical sources comprise electric dipoles.

5. The method of claim 1 , wherein the electrical current in the one or more of the plurality of segments when the well is back in its original shape is determined based at least partially upon an azimuthal angle, an inclination angle, or both for the one or more of the plurality of segments when the well is back in its original shape.

6. The method of claim 1 , further comprising performing an EM telemetry measurement-while-drilling (MWD) job in response to the estimated EM telemetry signal.

7. A method for modeling an electromagnetic (EM) telemetry signal, comprising:
replacing a first well with equivalent electrical sources in a model;
determining an electrical current in one or more segments in the first well based at least partially upon the equivalent electrical sources;
generating a simulated electrical current in a second well;
determining a normalized voltage in the one or more segments in the first well in response to the simulated electrical current in the second well;
determining a segment voltage in the one or more segments in the first well based at least partially upon the electrical current of the one or more segments in the first well and the normalized voltage of the one or more segments in the first well; and
estimating the EM telemetry signal from a transmitter in the first well based at least partially upon the segment voltages of the one or more segments in the first well.

8. The method of claim 7 , wherein replacing the first well with the equivalent electrical sources in the model comprises:
straightening the first well in the model;
dividing the first well into the one or more segments; and
determining the electrical current in the one or more of the segments in the first well when the first well is straightened.

9. The method of claim 8 , wherein electrical currents in the equivalent electrical sources are determined in the one or more of the segments in the first well when the first well is straightened.

10. The method of claim 8 , wherein replacing the first well with the equivalent electrical sources in the model further comprises:
bending the first well back into its original shape in the model; and
determining an electrical current in the one or more of the segments in the first well by projection when the first well is back in its original shape.

11. The method of claim 7 , wherein determining the segment voltage in the one or more segments in the first well comprises multiplying the electrical current in the one or more segments in the first well by the normalized voltage in the one or more segments in the first well.

12. The method of claim 7 , wherein estimating the EM telemetry signal comprises summing the segment voltages for the one or more segments in the first well.

13. The method of claim 7 , wherein the EM telemetry signal is estimated at a sensor in the second well.

14. The method of claim 7 , wherein the second well comprises a metallic casing.

15. The method of claim 7 , wherein the equivalent electrical sources comprise electric dipoles.

16. The method of claim 7 , further comprising drilling the first well in response to the estimated EM telemetry signal.

17. A computing system comprising:
one or more processors; and
a memory system comprising one or more non-transitory computer-readable media storing instructions that, when executed by at least one of the one or more processors, cause the computing system to perform operations, the operations comprising:
replacing a first well with equivalent electrical sources in a model;
determining an electrical current in one or more segments in the first well based at least partially upon the equivalent electrical sources;
generating a simulated electrical current in a second well;
determining a normalized voltage in the one or more segments in the first well in response to the simulated electrical current in the second well;
determining a segment voltage in the one or more segments in the first well based at least partially upon the electrical current of the one or more segments in the first well and the normalized voltage of the one or more segments in the first well; and
estimating an electromagnetic (EM) telemetry signal from a transmitter in the first well based at least partially upon the segment voltages of the one or more segments in the first well.

18. The computing system of claim 17 , wherein replacing the first well with the equivalent electrical sources in the model comprises:
straightening the first well in the model;
dividing the first well into the one or more segments;
determining the electrical current in the one or more of the segments in the first well when the first well is straightened;
bending the first well back into its original shape in the model; and
determining an electrical current in the one or more of the segments in the first well by projection when the first well is back in its original shape.

19. The computing system of claim 17 , wherein determining the segment voltage in the one or more segments in the first well comprises multiplying the electrical current in the one or more segments in the first well by the normalized voltage in the one or more segments in the first well.

20. The computing system of claim 17 , wherein the operations further comprise performing an EM telemetry measurement-while-drilling (MWD) job in response to the estimated EM telemetry signal.

Assignees

• Schlumberger Technology Corp

Inventors

• Chen Jiuping
• Jannin Gaelle
• Sun Liang

Classifications

• E21B47/13 Primary

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

• E21B7/10 Primary

  Correction of deflected boreholes · CPC title

• H04B17/391

  Modelling the propagation channel · CPC title

• G01V3/02

  operating with propagation of electric current · CPC title

• G01V11/002

  Details, e.g. power supply systems for logging instruments, transmitting or recording data, specially adapted for well logging, also if the prospecting method is irrelevant (means for transmitting well survey signals E21B47/12; signal transmission systems in general G08C; transmission in general H04B) · CPC title