In recent years, fracture-controlled (hydrothermal) dolomitization in association to igneous activity has gained interest in hydrocarbon exploration. The geometry and distribution of dolomite bodies in this setting are of major importance for these new plays. The Latemar platform presents a spectacularly exposed outcrop analogue for carbonate reservoirs affected by igneous activity and dolomitization.
LiDAR scanning and digital outcrop models (DOM) of outcrops offer a great opportunity to derive geometrical information. Only few analysis methods exist to quantitatively assess huge amounts of georeferenced 3D lithology data. This study presents a novel quantitative approach to describe 3D spatial variation of lithology derived from DOMs. This approach is applied to the Latemar platform to determine dolomite body geometry and distribution in relation to crosscutting dikes.
A high-resolution photorealistic DOM of the Latemar platform allows description of dolomite occurrences in three dimensions, with high precision on platform-scale. This results in a unique lithology dataset of limestone, dolomite and dike positions. This dataset is analysed by true 3D variography for the geospatial description of dolomite distribution. In most studies, 3D geostatistics is the combination of 2D horizontal and 1D vertical variation. In this study the dolomite occurrences are extensive in 3D and cannot be reduced to a 2D+1D case. Therefore the concept of 2D variogram maps is expanded to a 3D description of lithology variation. 3D anisotropy detection is used to derive principal directions in the occurrence of dolomite.
Two small-scale (<200 m) anisotropy directions emerge, one vertical and one subhorizontal, that describe the geometry of the dolomite bodies. These principal directions are perfectly aligned parallel to the average dike orientation. On platform-scale (200-1600 m) a bedding-parallel anisotropy direction indicates stratigraphic control on dolomite occurrences.