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Distribution and Geometry of Dolomite Bodies in Association With Igneous Activity (Latemar, Northern Italy)

Abstract

Dolomitization in association with igneous activity has gained increased attention because of its potential as hydrocarbon reservoirs. Understanding spatial distribution, geometry and connectivity of dolomite bodies and the effect of dolomitization on reservoir properties is of key importance for the evaluation of business opportunities, optimization of development and production plan of carbonate reservoirs. While primary dolomite is mainly controlled by sequence stratigraphy, facies distribution and platform geometry, hydrothermal dolomite is commonly observed associated to faults and igneous bodies and typically shows complex spatial distribution and geometry. We present field and remote sensing data from an outcrop analogue to document the geometry and spatial distribution of dolomite bodies originating from the interaction between carbonates and dykes to determine the main controls on dolomite distribution. The Latemar platform (N-Italy), Anisian-Ladinian in age is a spectacularly exposed example of carbonate platform that has been intruded by dykes immediately after deposition and was subsequently dolomitized. Field data was complemented with high-resolution remote sensing data on LiDAR-derived 3-D photorealistic models. Dolomite and limestone occurrences are manually picked on the digital models and verified in the field resulting in a 3-D point set with lithology classification. A new approach was designed to quantitatively extract 3-D lithology variation. By means of 3-D variography (not just 2D horizontal + 1D vertical) the occurrence and geometry of dolomite bodies are described and reveal multi-scale (an) isotropy of lithology variability. Interpolation of lithology based on 3-D lithology variography description, in combination with porosity and permeability data, allows direct construction of accurate reservoir models for dolomite reservoir development. Results presented here are the first quantitative 3-D description of dolomite bodies in a carbonate platform affected by igneous activity. Small-scale dolomite bodies (<200 m) are vertically and horizontally elongated bodies that often crosscut each other and whose principal axis is parallel to the dykes. Small-scale dolomite bodies form a complex network whose geometry and heterogeneity imparted to the reservoir is strongly controlled by orientation and spatial distribution of the dykes. Organization of dolomite bodies (>200 m) is controlled by major stratigraphic changes.