Geophysical Data in 3-D Geographic Information Systems (GIS)

Grace, John D.¹ (1) Earth Science Associates, Long Beach, CA

Traditional applications of geographic information system (GIS) technology in upstream petroleum have been in two dimensions, usually restricted to the surface of the earth. The overwhelming majority of money spent by the industry, however, is for geophysical data: principally seismic and well logs, which are inherently three-dimensional. Although interpretations from these data are amenable to 2-D mapping, much is lost in the absence of simultaneous direct display and use of depth. The development of 3-D GIS promises to bridge this opportunity.

Geophysical data can enter 3-D GIS in two modes: as images of seismic sections and well logs or as vector data (where the digital information underlying the images is represented in points, lines, 2-D or 3-D polygons and 2-D or 3-D grids that are registered in all three dimensions). Images of seismic sections and logs provide very useful context and reference for other vector data (e.g., wells, completions, reservoir bodies, stratigraphic boundary surfaces). Images, however, cannot interact or be subjected to analytic operations and do not exploit the potential of GIS technology.

The greatest leverage to GIS for the massively valuable accumulated body of geophysical data is in their vector representation in 3-D GIS. As vectors, 3-D GIS tools can subject geophysical data to logical and spatial queries and classifications, as well as incorporate them in analytic models that take their 3-D locations and attributes as arguments. Examples are shown from the Gulf of Mexico using LAS data for well logs; SEG-Y data for seismic and vector representations of geophysical interpretations in 3-D GIS.