Magnetotelluric imaging of basalt-covered sediments (original) (raw)
Related papers
2017
The Paraná basin is a major Phanerozoic feature in Brazil and adjacent countries. Data from 261 MT stations distributed along 3 lines (P1, P2 and P3) have been inverted in 3D to reveal the resistivity structure from surface to 50km depth. The average station spacing is 1.8 km and the frequency bandwidth is 1000 to 0.001 Hz. 2D inversion was also done for comparison with an earlier roughly parallel regional line P0 and found to be consistent with our new 3D model. The goodness of our 3D model was first evaluated by comparison with data from 3 deep exploration wells within our study area. The 3D model correctly identified resistive (>100 Ωm) basalt cover, underlying conductive (~10 Ωm) sediments (up to 5-6 km thick) and resistive (>1000 Ωm) crystalline basement. The MT results are consistent with other geophysical anomalies previously observed in the study area; the segmented midcrustal resistive layer found in a zone of depressed Moho is interpreted as evidence of magmatic unde...
Sedimentary basins reconnaissance using the magnetic Tilt-Depth method
Exploration Geophysics, 2010
We compute the depth to the top of magnetic basement using the Tilt-Depth method from the best available magnetic anomaly grids covering the continental USA and Australia. For the USA, the Tilt-Depth estimates were compared with sediment thicknesses based on drilling data and show a correlation of 0.86 between the datasets. If random data were used then the correlation value goes to virtually zero. There is little to no lateral offset of the depth of basinal features although there is a tendency for the Tilt-Depth results to be slightly shallower than the drill depths. We also applied the Tilt-Depth method to a local-scale, relatively high-resolution aeromagnetic survey over the Olympic Peninsula of Washington State. The Tilt-Depth method successfully identified a variety of important tectonic elements known from geological mapping. Of particular interest, the Tilt-Depth method illuminated deep (3km) contacts within the non-magnetic sedimentary core of the Olympic Mountains, where magnetic anomalies are subdued and low in amplitude. For Australia, the Tilt-Depth estimates also give a good correlation with known areas of shallow basement and sedimentary basins. Our estimates of basement depth are not restricted to regional analysis but work equally well at the micro scale (basin scale) with depth estimates agreeing well with drill hole and seismic data. We focus on the eastern Officer Basin as an example of basin scale studies and find a good level of agreement between previously-derived basin models. However, our study potentially reveals depocentres not previously mapped due to the sparse distribution of well data. This example thus shows the potential additional advantage of the method in geological interpretation. The success of this study suggests that the Tilt-Depth method is useful in estimating the depth to crystalline basement when appropriate quality aeromagnetic anomaly data are used (i.e. line spacing on the order of or less than the expected depth to basement). The method is especially valuable as a reconnaissance tool in regions where drillhole or seismic information are either scarce, lacking, or ambiguous.
Magnetotelluric (MT) Method in Hydrocarbon Exploration: A New Perspective
Magnetotelluric (MT) method has been used for petroleum exploration MT worldwide, especially in reconnaissance stage of an exploration program and also in difficult areas due to topographic and structural complexity. However, application of MT in Indonesia is very limited due many restraining circumstances. The paper describes the basic principles of MT method and its potential application for hydrocarbon exploration. Examples using both synthetic and field data from typical overthrust structures are discussed.