f Advances in 3D seismic fault interpretation

We have designed a new procedure that combines fast horizon tracking and edge detection with precise 3-D editing to significantly improve the speed and quality offault interpretation on 3-D seismic workstations. The procedure works as foIIows: • First, we auto-track horizons at speeds 5 to 10 times faster than currently available on equivalent workstations. We achieve this speed improvement through the use of a proprietory technology. • Second, we detect horizon edges; an edge being the locus of points where the horizon dip and amplitude variation along the dip direction exceed thresholds that are interactively specified. • Third, we use a 3-D interactive editor that zooms in and edits automatically detected horizon edges with great precision. Editing is done on projections of the fault trace on three orthogonal planes. These planes are dynamically linked, so any change in one plane is concurrently updated in the other two planes, and also in a perspective rendering of horizons and fault edges. • Fourth, we assign edge segments belonging to the same fault to a common fault set. • Fifth, we augment the fault set of horizon edges with fauIt segments interpreted on vertical seismic sections. • Finally, we fit a surface through segments in the common fault set and render the surfacetogether with horizons in a 3-D perspective view. In order to avoid any ambiguity due to multi-valued surfaces, we use a data-adaptive coordinate system to fit the surface. In the case of subtIe faults, which are sometimes only visible as discontinuities on an attribute map, we perform edge detection on the attribute map instead of on the horizon dip and amplitude maps.