Changes

* Avoiding several pitfalls described herein

* Avoiding several pitfalls described herein

* Integrating the [[magnetics]] with seismic, subsurface, and other data

* Integrating the [[magnetics]] with seismic, subsurface, and other data

* Developing the basement fault block pattern from the magnetic data

* Developing the [[basement]] fault block pattern from the magnetic data

* Using concepts of basement control in working with all data sets

* Using concepts of basement control in working with all data sets

[[file:using-magnetics-in-petroleum-exploration_fig14-12.png|300px|thumb|{{figure number|1}}Magnetic profile on an interpreted seismic section from Logan County, Arkansas. Modified from Coleman and Roberts;<ref name=ColemanRoberts1991>Coleman, J. M., and H. H. Roberts, 1991, Mississippi River depositional system: model for the Gulf Coast Tertiary, in D. Goldthwaite, ed., An Introduction to Central Gulf Coast Geology: New Orleans Geological Society, p. 99–121.</ref> courtesy New Orleans Geological Society.]]

[[file:using-magnetics-in-petroleum-exploration_fig14-12.png|300px|thumb|{{figure number|1}}Magnetic profile on an interpreted seismic section from Logan County, Arkansas. Modified from Coleman and Roberts;<ref name=ColemanRoberts1991>Coleman, J. M., and H. H. Roberts, 1991, Mississippi River depositional system: model for the Gulf Coast Tertiary, in D. Goldthwaite, ed., An Introduction to Central Gulf Coast Geology: New Orleans Geological Society, p. 99–121.</ref> courtesy New Orleans Geological Society.]]

Magnetics can be very valuable in interpreting [[seismic data]] by plotting residual magnetic profiles along seismic sections. This technique is valuable in looking for (1) subtle stratigraphic changes that can occur along basement block boundaries and (2) subtle fault offsets or other structural and stratigraphic features. The locations of the basement weakness zones provide focal points for examining the seismic data more closely.

Magnetics can be very valuable in interpreting [[seismic data]] by plotting residual magnetic profiles along seismic sections. This technique is valuable in looking for (1) subtle stratigraphic changes that can occur along [[basement]] block boundaries and (2) subtle fault offsets or other structural and stratigraphic features. The locations of the basement weakness zones provide focal points for examining the seismic data more closely.

[[:file:using-magnetics-in-petroleum-exploration_fig14-12.png|Figure 1]] shows an example of a magnetic profile on an interpreted seismic section from Logan County, Arkansas. The dark band corresponds to Cambrian through Mississippian sedimentary rocks. Note correlation between the location of the four normal faults interpreted in the seismic section and the location of faults in the magnetic profile (marked by diamonds).

[[:file:using-magnetics-in-petroleum-exploration_fig14-12.png|Figure 1]] shows an example of a magnetic profile on an interpreted seismic section from Logan County, Arkansas. The dark band corresponds to Cambrian through Mississippian sedimentary rocks. Note correlation between the location of the four normal faults interpreted in the seismic section and the location of faults in the magnetic profile (marked by diamonds).

==Magnetics vs. other techniques==

==Magnetics vs. other techniques==

We might question the strong emphasis on magnetics for mapping the basement fault block pattern. However, is there any other way to reliably map this pattern beneath the sedimentary section? Methods that depend on surface information—Landsat, SLAR, conventional photo geology, and surface geology—are of limited value. That leaves only gravity and seismic techniques.

We might question the strong emphasis on magnetics for mapping the [[basement]] fault block pattern. However, is there any other way to reliably map this pattern beneath the sedimentary section? Methods that depend on surface information—Landsat, SLAR, conventional photo geology, and surface geology—are of limited value. That leaves only gravity and seismic techniques.

However, gravity techniques generally do not separate adjacent basement blocks because of the lack of density contrast between adjacent blocks and because of interference from density differences within the sedimentary section. On seismic data, the basement reflector is often difficult to recognize beneath complex structure and because of a lack of velocity contrast with the dense dolomites that overlie the basement in many areas. Furthermore, both seismic and gravity methods are expensive to apply over broad areas and cannot provide even a tiny percentage of the area coverage that can be obtained with magnetics for the same price.

However, gravity techniques generally do not separate adjacent basement blocks because of the lack of density contrast between adjacent blocks and because of interference from density differences within the sedimentary section. On seismic data, the basement reflector is often difficult to recognize beneath complex structure and because of a lack of velocity contrast with the dense dolomites that overlie the basement in many areas. Furthermore, both seismic and gravity methods are expensive to apply over broad areas and cannot provide even a tiny percentage of the area coverage that can be obtained with magnetics for the same price.