3-D numerical seismic stratigraphic model generated from a highly anisotropic and wide- meshed survey grid.
Recently, 55 high-resolution seismic sections were collected by the Geological Survey of Canada to map the Quaternary sedimentary succession over an area of 7600 km2 in the St. Lawrence Estuary (eastern Canada). To better understand the geometrical relationships between these various units and to document the impact of the bedrock topography on the Quaternary basin infill, a numerical seismic stratigraphic model was developed. The main challenges related to its realization were the highly anisotropic character of the seismic grid due to the N330 orientation of most sections and the spacing between the sections ranging from 2.5 to 10 km. On each section, horizon picking of the key seismic unit boundaries generated a point coverage (x,y,z) that was later converted into curves. The dataset was sampled to increase the ratio between the distance of the neighbouring points and the distance between the curves. Control curves parallel to the basin axis were also created to constrain major topographic features to be modelled. Then, preliminary surfaces representing the superior limit of the seismic units were built with a discrete smooth interpolator by using the curves. This interpolator was robust enough to link the curves together with a minimum global roughness even if they were separated by a significant distance. The original point coverage was subsequently used as control nodes that forced the preliminary surfaces to be connected to the points. The influence of the wide-meshed character of the survey grid on the quality of the surface rendering was also corrected by using an equilateral triangulated mesh that included as many equilateral triangles as possible. Moreover this step made the surfaces more stable for numerical calculations. The resulting surfaces were used to create a volume model of 11 520 km3 that has horizontal and vertical resolutions of 250 and 5 m respectively. This model reflects adequately first order features such as dip and thickness variations of seismic units. It is also in agreement with more subtle features such as discontinuous bedrock highs that have been independently imaged on multibeam bathymetry. Depth slices and cross-sections can be easily extracted from the 3-D model and volume calculations can be done to improve geological interpretations in the area. The workflow used represents an effective way to generate a numerical model at the basin scale based on data collected according to a highly anisotropic and wide-meshed survey grid.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 9810 New fields (not classifiable under other headings);
- 9820 Techniques applicable in three or more fields