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GCConstraining Seismic
Interpretation
with Aeromagnetic
Data
*
John W. Peirce1
Search and Discovery Article #40606 (2010)
Posted October 14, 2010
*Adapted from the Geophysical Corner column, prepared by the author and entitled “HRAM Data
Gives Perspective,” in AAPG Explorer, September, 2005. Appreciation is expressed to Alistair Brown, editor of Geophysical Corner, and to Larry Nation, AAPG Communications Director, for their support of this online version.
1GEDCO, Calgary, Alberta, Canada ([email protected])
Magnetic data
traditionally have been used to map basement faulting, allowing geoscientists to have a better understanding of the structure of the overlying sedimentary section. Recent advances in acquisition, processing and
interpretation
techniques, however, have made it possible to map intra-sedimentary faulting and fractures as well. HRAM (high-resolution aeromagnetic)
data
are acquired by flying a plane with a magnetometer approximately 100-150 meters from ground surface over an area of exploration interest on a grid with line spacing of 200-800 meters. When flying close to the ground, the magnetometer senses magnetic variations caused by basement crystalline rocks, as well as the subtle variations from the sedimentary section, near surface geological signals and cultural noise from wells, pipelines, and other ferrous structures. The processing and
interpretation
of HRAM
data
becomes a task of integration with all available
data
. At this point the magnetic
data
show a general distribution of magnetic properties demonstrating broad regional trends.
|
Interpretive Processing and Results It is important to highlight as much structure as possible through interpretive processing. This is accomplished through various filters, creating a montage of several maps. The processing geophysicist uses the power spectrum of the The result is a set of enhanced magnetic anomaly maps that highlight lineaments that are due to geological features in the basement and in the sedimentary section, separated by wavelength (longer wavelengths mean deeper sources; shorter wavelengths mean shallower sources). Further perspective can be added by calculating magnetic depth solutions to see faults and structural grain, and by displaying these in a 3-D visualization cube with the There is strength in numbers; the ambiguity of separate interpretations drops dramatically with each constraint from a different type of
In the IEA Weyburn CO2 sequestration project, a large amount of 2-D Because the faulting patterns were somewhat complicated and the The situation is made more complicated because the In addition to demonstrating the utility of using HRAM
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