Magnetotelluric survey case history: volcanic terrain (Columbia River Plateau)

Exploring for Oil and Gas Traps
Series	Treatise in Petroleum Geology
Part	Predicting the occurrence of oil and gas traps
Chapter	Applying magnetotellurics
Author	Arnie Ostrander
Link	Web page
Store	AAPG Store

Seismic methods do not work well in areas covered by volcanics because of the dispersive nature of the volcanics and because of the decrease in acoustic velocity at the base of the volcanics.

Volcanic terrain, however, is an ideal environment for MT because it is a simple, three-layer stratigraphic package: resistive basalts over conductive sediments, which in turn overlie resistive metamorphic or granitic basement rocks.

Survey results

Figure 1 13-station MT natural source survey profile. Drafted from data from Mills.

Figure 1 is a 13-station MT natural source survey profile. This east-west section begins near the Idaho-Washington border and extends approximately length::75 mi (120 km) to the west (Mills, personal communication, 1994).

Structural details

These data provided the following structural details:

• Considerable variation on the thickness of the volcanics
• Considerable variation in the depth to top of basement
• Basalts thin to the east
• Sediments thin to east and eventually disappear
• Basement resistivities are an order-of-magnitude higher on the east end of the profile

Controlled-source MT data could provide 3-D imaging of individual prospects.

See also

• Magnetotellurics
• Magnetotellurics survey measurements
• Magnetotelluric data acquisition
• Magnetotellurics case history: frontier basin analysis (Amazon Basin, Colombia)
• Case history: rugged carbonate terrain (Highlands of Papua New Guinea)
• Case history: Precambrian overthrust (Northwestern Colorado)

External links

find literature about Magnetotelluric survey case history: volcanic terrain (Columbia River Plateau)

• Original content in Datapages
• Find the book in the AAPG Store

middle tubing