A fast computation of 2-D gravity and magnetic models on a modern color graphics work station

Abstract EN

Forward modeling is the principal technique used by earth scientists for quantita- tive interpretation of measured gravity and magnetic data for oil and mineral exploration.

Ob- jectives of the interpretation include to gain insight into the subsurface geology for use in locat- ing a prospect or for planning more extensive geophysical surveys.

A software package to facilitate two-dimensional forward modeling of gravity and magnetic data was developed on a color graphics work station at the ARAMCO EX PEC Computer Centre.

The forward modeling procedure is iterative., and consists of three steps.

1.

To postulate a 2-dimensional geologic model including density and susceptibility proper- ties as well as geologic structure.

2.

To compute the theoretical gravity and magnetic response, and 3.

To compare the computed response with measurements.

Iterations are performed by adjusting the model and repeated steps two and three until a satisfactory match is obtained between computed and measured results.

Interactive editing functions implemented in the software package make it easy to adjust the model.

Modeling can be done in either 2.

2.5 or 3 dimensions.

Two dimensional modeling involves defining geologic structure in cross-section and assumes that the structural unit has infinite strike extent.

In 2.5-D modeling unit has infinite strike extent.

In 2.5-1) modeling, the struc- ture is still defined in cross-section, but strike extent may be specified tor each structural unit.

The modeling program includes the following facilities: continuous uscr-computcr dialog, flexible model editing, fast computations, point-and-click menu selections, and hard-copy graphical output.

An automatic model adjustment option is being added so that the user may choose to have the algorithm automatically adjust the model parameters within selected con- straints.