Integration of terrestrial laser scanning, digital photogrammetry and geostatistical methods for high-resolution modelling of geological outcrops

Like many fields in the earth sciences, geology is a rapidly expanding application area demanding spatial information, brought about mainly by the recent advances in geomatics technology. One area of high interest is the study of sedimentary rock outcrops, which can be used as direct analogues for the configurations of producing oil and gas fields in the subsurface. Such outcrop analogues are exposed areas of rock, ideally with strong three-dimensional properties, such as river-cut canyons or quarries, where it is possible for the geologist to study systems that are geometrically comparable to hydrocarbon-bearing rocks. As hydrocarbon reservoirs are typically inaccessible, spatial data are scarce, typically restricted to low resolution seismic surveys and a very limited number of boreholes. This makes the study of such systems problematic, and the application of outcrop analogues has long been used to infer much of the missing detail. However, in the past, spatial data acquisition techniques have been relatively crude, meaning that geological models and interpretation have been lacking in geometric detail and accuracy. Advances made to digital photogrammetry and terrestrial laser scanning have made geologists more aware of the potential of geomatics, and this is beginning to have an influence on such analogue studies. This paper therefore explores this new application field, and highlights many of the modelling tasks that are intrinsically linked to spatial information science. Terrestrial laser scanning and photogrammetry were used to capture detailed point clouds and imagery of outcrops, which were processed to form textured digital surface models. From these high-resolution, high-accuracy datasets, geological features were extracted, which form the basis for building geo-cellular models comparable to those used to model subsurface reservoirs, allowing direct comparison between the outcrop and the subsurface.