Using Geological Expression Techniques to Reveal Complex Regional Structural Information without Conventional Interpretation

Wooltorton, Tom

The workflows applied in the interpretation of regional structure in post-stack 3-D seismic datasets are very much a legacy of techniques developed when 2-D seismic first arose to prominence decades ago as a regional mapping tool, and interpreters used pencil and paper to carry out their analyses. Nowadays, despite the vast quantities of data contained in high-resolution 3-D surveys and the availability of high-end processing machines, the techniques most commonly applied have not advanced significantly.

Principally, structural interpretation of 3-D seismic is achieved through the manual picking of faults on inlines and crosslines, interpolating picks into surfaces, and then defining the geological context of the extracted results. Occasionally this will be aided by discontinuity-highlighting attributes or automated fault extraction techniques. It is then up to the geoscientist to determine whether the interpretation makes sense or what conclusions can be drawn. This can be inefficient for several reasons: firstly, manual interpretation is very time consuming. Secondly, there is a high risk of subjectivity, particularly where the image is poor. Work may also be rushed or details insufficiently examined.

This paper outlines the techniques applied and conclusions derived from fully-3-D analysis of a 3-D dataset, using Geological Expression techniques, in order to determine what results can be obtained without manual picking. The goal of Geological Expression is to define distinct geological elements within the seismic, using data driven but interpreter guided processes to carry out analysis. The techniques include analysis of structural orientations within the data using volumetric dip and azimuth, extraction and analysis of different generations of faulting, and integration with knowledge of other exploration goals in the region.

After illuminating the data in terms of separate geological domains, with clearly identifiable structural regimes and bounding surfaces, the analysis highlighted results that can be confidently interpreted as fault extension and reactivation through a regional capping lithology, which represents a notable seal failure risk. The use of volumetric techniques provided a basis for quantitative analysis to validate the ongoing interpretation. It was also found that the time taken to complete the analysis was significantly shorter than conventional interpretation techniques for this data.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013