Depth estimates are often used to delineate geologic structures that produce a magnetic or gravity anomaly. In oil and gas exploration, this is equivalent to determining the maximum thickness of the sedimentary section.
Geosoft’s Euler 3D requires data to be processed and gridded prior to analysis – vertical derivative (dz), and horizontal derivative (dx & dy) grids are required.
(Geosoft also offers a montaj MAGMAP extension, which may be used to create the prerequisite vertical and horizontal derivative grids.)
The location and depth of gravity and magnetic sources can be determined using the Euler 3D deconvolution system. It is designed to guide the user through data preparation, processing, analysis and visualization. It can also:
- Choose a structural index (any real value between 0.0 and 3.0),
- Adjust the depth tolerance and window source distance,
- Adjust the data window size and easily calculate the depth of magnetic sources.
- Original grid
The Keating Magnetic Correlation Coefficients Tool for Kimberlite Exploration, utilizes a simple pattern recognition technique to locate magnetic anomalies that resemble the response of modelled Kimberlite pipes.
Keating’s method utilizes a simple pattern recognition technique to locate magnetic anomalies that resemble the response of a modelled kimberlite pipe. The magnetic response of a vertically dipping cylinder is computed in grid form. The model parameters that may be adjusted include the depth, radius and magnetic intensity as a “moving window”.
The correlation between modelled and observed data is computed at each grid node using a firstorder regression and archived. The correlation coefficients that exceed a specific threshold (e.g., 75%) are retained for comparison to the magnetic and other exploration data.
The Source Edge Detection (SED) function locates edges (i.e. geological contacts) or peaks from potential field data by analyzing the local gradients. The SED function estimates the location of abrupt lateral changes in magnetization or mass density of upper crustal rocks. Its procedure is to identify maxima on a grid of horizontal gradient magnitudes.
Using the technique of Cordell and Grauch (1982, 1987) a database of source edge locations are derived from a grid of total magnetic field or gravity. A map is produced with symbols representing locations and gradient directions of potentaial field anomalies. You can distinguish between gradients that are in 1, 2, 3, or 4 directions.
