Method and apparatus for passive detection of near-surface human-scale underground anomalies using earth field measurements

• US 10,156,134 B2
• Filed: 08/01/2017
• Issued: 12/18/2018
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Terra Response, LLC
• Original Assignee: Terra Response, LLC
• Inventors: Smith, James E., Pertl, Franz A., Nutter, Roy S., Lowery, Andrew D.
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): MCANDREW, CHRISTOPHER P
• Application Number:
  US15/666,478
• Publication Number:
  US 20170356285A1
• Time in Patent Office: 504 Days
• Field of Search: 324326
• CPC Class Codes: E21B 47/09 Locating or determining the position of objects in boreholes or wells , e.g. the position of an extending arm; Identifying the free or blocked portions of pipes
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat

Abstract

A method for detecting a subsurface anomaly at a near-surface depth, comprises positioning an electromagnetic sensor configured to measure a component of a planetary electromagnetic field such that the electromagnetic sensor is suspended just above a ground-air barrier and does not contact a ground surface; selecting an electromagnetic frequency by calculating a function of properties of the ground that include relative permittivity, relative permeability, and resistivity; moving the electromagnetic sensor over the surface of the ground; repeatedly measuring intensity of the component of the planetary electromagnetic field at the frequency to obtain a set of measurements; and comparing at least a first measurement in the set of measurements to at least a second measurement in the set of measurements to identify a change in the intensity of the component of the planetary electromagnetic field that is indicative of a presence of a subsurface anomaly.

Claims

1. A computer-implemented method for detecting a subsurface anomaly at a near-surface depth, comprising the steps of:

positioning an electromagnetic sensor that is configured to measure a component of a planetary electromagnetic field such that the electromagnetic sensor is suspended just above a ground-air barrier and does not contact a ground surface;

selecting an electromagnetic frequency by calculating, with a computing device, a function of properties of the ground that include relative permittivity, relative permeability, and resistivity;

moving the electromagnetic sensor over the surface of the ground;

repeatedly measuring intensity of the component of the planetary electromagnetic field at the frequency to obtain a set of measurements; and

comparing, with the computing device, at least a first measurement in the set of measurements to at least a second measurement in the set of measurements to identify a change in the intensity of the component of the planetary electromagnetic field that is indicative of a presence of a subsurface anomaly.

2. The method of claim 1, wherein the selected frequency is at least 5 kilohertz (kHz).

3. The method of claim 2, wherein the subsurface anomaly is human-scale.

4. A computer-implemented method for determining depth of a subsurface anomaly at a near-surface depth, comprising the steps of:

positioning an electromagnetic sensor that is configured to measure a component of a planetary electromagnetic field such that the electromagnetic sensor is suspended just above a ground-air barrier and does not contact a ground surface;

selecting a first electromagnetic frequency by calculating, with a computing device, a function of properties of the ground that include relative permittivity, relative permeability, and resistivity;

selecting a second electromagnetic frequency by calculating, with a computing device, a function of properties of the ground that include relative permittivity, relative permeability, and resistivity;

moving the electromagnetic sensor over the surface of the ground;

repeatedly measuring intensity of the component of the planetary electromagnetic field at each of the first frequency and the second frequency to obtain a set of measurements;

determining, with the computing device, which of the first electromagnetic frequency and the second electromagnetic frequency exhibits a greater change in intensity attributable to the subsurface anomaly; and

calculating, with the computing device, a depth of the subsurface anomaly;

wherein calculating the depth is based at least in part on measured intensity, at the electromagnetic frequency determined to exhibit the greater change in intensity, of the component of the planetary field.

5. The method of claim 4, wherein the first electromagnetic frequency and the second electromagnetic frequency are each at least 5 kHz.

6. The method of claim 5, wherein the subsurface anomaly is human-scale.