Synergistic Interpretation
of Near-Surface Magnetic
Anomalies and High-Frequency
Seismic
Data
, Northeastern Montana
John A. Andrew, Robert J. Graf, Douglas P. O'Brien, Richard J. Wold
A low-altitude (300-ft), close-spaced (4 lines/mi) airborne magnetic
gradiometer survey was flown in a 1,000-mi2 area in northeastern
Montana. The area contains 31 oil fields and a modern high-frequency,
broad-bandwidth seismic
data
set. The aeromagnetic survey was designed
specifically to study and analyze the short-wavelength, small-amplitude magnetic
anomalies associated with near-surface magnetic sources. Some near-surface
magnetic sources may be related to epigenetic changes associated with seeps from
hydrocarbon reservoirs.
All 31 oil fields had a near-surface magnetic anomaly. Other near-surface
magnetic anomalies had an obvious seismic
anomaly visible on the high-frequency,
broad-bandwidth
seismic
data
available in the area. In addition, the zones
offsetting the observed near-surface magnetic anomalies can be seen in the
seismic
data
, suggesting a small, but deep-seated Quaternary or Holocene
wrench-fault system. Many of the magnetic offset zones were also visible in
available Landsat
data
. These offset zones may provide the vertical migration
paths for reservoir seeps.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.