Abstract

Detecting small faults and fractures is critical when studying reservoir compartmentalization. Subtle features that are not identifiable using conventional 3D seismic can be highlighted using seismic attributes. Advances in this technology have been achieved in the geophysical laboratory at the University of Houston. We have successfully applied 3D seismic attributes that enable us to interpret very small structural and stratigraphic features not previously detected.

The Dollarhide Field is one example of the successful use of this technology. The field is interpreted as a structural trap bounded by NS-trending, reverse faults on its eastern flank. It is also cut by NE-trending, high-angle, right-lateral, strike-slip faults with 100 to 200 feet of normal or reverse displacement, and minor, high angle, NW-trending faults. Porosity-feet maps of two major reservoirs in the field show evidence of compartmentalization that does not correspond exactly with previously interpreted faults.

We computed attribute volumes from the full input 3D data volume across this field and extracted the attribute values along picked horizons. The most useful attributes for detecting subtle geologic structures were coherence time slices with edge-preserving smoothing, horizontal derivatives of coherent energy without smoothing, and eigenvector-derived dip and dip-azimuth. Based on these attributes, we identified an additional set of small, NW-trending faults and a swarm of minor faults parallel to the NE-trending, right-lateral strike-slip faults. The newly interpreted faults show an improved correspondence to the compartmentalization based on field performance data of the previously noted field.