Overview

The field of structural geology is fully as broad and complex as petroleum seismology. It would be an endless diversion to give even an overview of structure concepts and methods. We must assume a basic understanding of deformation, static stress and strain, rock failure, fault types and occurrence, and large-scale tectonic influence on local structural elements. It is the combination of petroleum seismic data and expertise in structural geology that forms a powerful tool for structural analysis.

Mapping the structure of a 3D reflection surface involves the use of both horizontal and vertical sections in the data cube. Vertical sections afford the best view of general structural style and correlation of events across faults, but can be misleading due to apparent dip. Even in a 3D data cube, observed dips (or seismic slopes) are apparent unless the vertical section is extracted in the local dip direction. In horizontal sections, automatic time structure contours are seen by the intersection of each reflection event, analogous to a geologic subcrop map. This view also gives a direct estimate of horizontal resolution, is the primary tool for fault location and connectivity analysis, and shows true strike leading to true dip.

The 3D seismic gives a much better map of fault patterns than any grid of 2D seismic lines. It is usually the case that an area previously mapped with 2D data and remapped with 3D data will show an increase in the number and orientation of faults. This can dramatically alter reservoir engineering...