SYSTEM AND METHOD FOR GEOPHYSICAL SURVEYING USING ELECTROMAGNETIC FIELDS AND GRADIENTS

摘要

Electromagnetic exploration methods are used to identify a subsurface anomalous feature. This is sometimes difficult in the presence of large fields from the transmitter or other surrounding material that may be above and around the subsurface feature. By constructing linear combinations of the field and gradients of the field it is possible to remove the large fields associated with the transmitter and the surrounding material to make identification of the anomalous subsurface material easier. The fields and gradients can also be combined so as to provide estimates of other electromagnetic field quantities that would be otherwise difficult to measure, for example the electric field or the time derivative of the electric field.

主权项

1. A method for processing electromagnetic field measurements from a survey of an underground target embedded in a background material, the method comprising:
receiving the electromagnetic field measurements that are indicative of the underground and the underground target; applying at least one spatial derivative to the electromagnetic field measurements to calculate an indicator, wherein the indicator has a first value for a uniform portion of the underground and the indicator has a second value, different from the first value, for the underground target, such that measurements associated with the underground target are enhanced and measurements associated with a background material or a primary electromagnetic field are suppressed; and based on the first and second values of the indicator, identifying a location of the underground target.