Chapter 5
High-resolution Ground-magnetic (HRGM) and Radiometric Surveys for Hydrocarbon Exploration: Six Case Histories in Western Canada

Leonard A. LeSchack
Hectori Inc.
Calgary, Alberta, Canada

David R. Van Alstine
Applied Paleomagnetics, Inc.
Redmond, Washington, U.S.A.

ABSTRACT

In Western Canada, and probably elsewhere around the world, "magnetically enhanced zones" above microseeping hydrocarbon reservoirs can exhibit distinctive magnetic signatures that are characteristic of the reservoir. These distinctive magnetic signatures have proven to be invaluable for hydrocarbon exploration, and we have achieved 85% exploration success using ground-based magnetic and radiometric techniques in Western Canada. Differences in timing and duration of microseepage and differences in composition and pressure of the microseeping hydrocarbon gases from separate petroleum systems probably control the magnetic mineralogy, magnetic grain-size distributions, magnetic susceptibility, and natural remanent magnetization (NRM) directions in the magnetically enhanced zones. Together, these differences can yield diagnostic "residual" (remanent + induced) short-spatial-wavelength magnetic anomalies above different reservoirs.