US 2021/0063598 A1 · METHOD FOR REMOVING THE EFFECT OF NEAR SURFACE GALVANIC DISTORTION IN SURFACE TO BOREHOLE EM MEASUREMENTS

Abstract

A system and method of evaluating and correcting for the effects of a near-surface anomaly on surface-to-borehole (STB) measurement data in a geological halfspace comprises transmitting electromagnetic radiation from an EM source located on a ground surface which is positioned over the near-surface anomaly, measuring EM fields at a plurality of remote EM receivers located on the surface at a far distance from the EM source, obtaining vertical STB measurement data downhole, determining an orientation and moment of a secondary source equivalent dipole associated with the near-surface anomaly excited by the radiation transmitted by the EM source based on measurements of the EM fields at the plurality of remote receivers, determining a correction factor for the secondary source equivalent dipole on the EM field measurements at the plurality of remote receivers, and removing the effects of the near surface anomaly on the vertical STB measurement data using the correction factor.

Claims14

Dependent claims

A method of evaluating and correcting for effects of a near-surface anomaly on surface-to-borehole (STB) measurement data in a geological halfspace, the method comprising:

transmitting electromagnetic radiation from an EM source located on a ground surface which is positioned over the near-surface anomaly;
measuring EM fields at a plurality of remote EM receivers located on the surface and at a far distance from the EM source;
obtaining vertical STB measurement data downhole in a borehole located within the halfspace;
determining an orientation and moment of a secondary source equivalent dipole associated with the near-surface anomaly excited by the radiation transmitted by the EM source based on measurements of the EM fields at the plurality of remote receivers;
determining a correction factor for the secondary source equivalent dipole on the EM field measurements at the plurality of remote receivers;
and
removing the effects of the near surface anomaly on the vertical STB measurement data using the correction factor.

4 more elements

A system for evaluating and correcting for effects of a near-surface anomaly on surface-to-borehole (STB) measurement data in a geological halfspace, the system comprising:

an EM source adapted to transmit EM radiation located on a ground surface which is positioned over the near-surface anomaly;
a plurality of remote EM receivers located on the surface at a far distance from the EM source;
a downhole receiver positioned in a borehole within the halfspace adapted to obtain vertical STB electromagnetic field measurements;
and
a computing device configured, using computer-executable instructions, to:
receive measurements of EM fields from the plurality of remote EM receivers and the downhole receiver;
determine an orientation and moment of a secondary source equivalent dipole associated with the near-surface anomaly excited by the radiation transmitted by the EM source based on measurements of the EM fields at the plurality of remote receivers;
determine a correction factor for the secondary source equivalent dipole on the EM measurements at the plurality of remote receivers;
and
remove the effects of the near surface anomaly on vertical STB measurements obtained by the downhole receiver using the correction factor.

7 more elements

Dependencies are inferred from the claim text.

Method for removing the effect of near surface galvanic distortion in surface to borehole em measurements

Life of this patent

Method for removing the effect of near surface galvanic distortion in surface to borehole em measurements

Life of this patent

Abstract

Claims14