Patent ID: 8165815
Filing Date: 2012-04-24
Classification: G01V

Abstract:
1. A method for reducing the amount of source signal reaching a receiver through an air wave path (air wave noise), or reducing magnetotelluric (MT) noise at the receiver, in the course of electromagnetic field measurements in a controlled source electromagnetic survey of a subterranean region, comprising: (a) deploying a primary electromagnetic source and at least one receiver; (b) deploying a second electromagnetic source with its output signal designed to reduce air wave and MT noise by active cancellation in combined measured responses of the two sources operating simultaneously; and (c) activating the sources and collecting data at the one or more receivers; wherein active cancellation means cancellation accomplished by survey equipment deployment and design rather than by data processing, said active cancellation occurring in the medium or media in which electromagnetic energy is propagated from the two sources.