Application of Numerical Modelling to a Case of Compaction Driven Dolomitization: a Jurassic Paleohigh in Southern Alps, Italy
Paola Ronchi1, Alberto Consonni2, Alfredo Battistellli3, Claudio Geloni3, Giovanni Gianelli4, Domenico Grigo2, and Andrea Ortenzi1
1SPES, Eni E&P, San Donato Milanese, Italy
2GEBA, Eni E&P, San Donato Milanese, Italy
3Snamprogetti, Fano, Italy
4IGG, CNR, Pisa, Italy
The dolomitization in a carbonate platform can occur at different times and in different diagenetic; the application of reactive transport modelling may help to select the model that best honours the mass balance, kinetic and thermodynamic constrains.
The subject of this study is an application of the reactive transport modelling (RTM) software ‘Toughreact’ (Xu, 2004) coupled with a basin simulator (SEBE3, Eni proprietary) in a case study of dolomitization interpreted as due to flux of basin waters into paleohigh carbonates in shallow burial realm (Jurassic of the Southern Alps). The collected data and approach are part of a R&D Eni proprietary project. The aim of the simulation was to strengthen the conceptual interpretation and to give insights on the distribution of dolomitization in the subsurface using a mass balance approach.
The modelling process was subdivided into parts; at first the reconstruction of the compaction fluid flow and its funnelling into the permeable paleohigh was calculated in a 3D setting, then the RTM was applied. Sensitivities on the dolomite precipitation kinetics and on the diagenetic fluid composition suggested that the dolomitization was an efficient process even at the low temperatures, and the main differences regards the process rate. The permeability is the most important factor influencing the fluid flow and consequently the dolomitization.
In terms of mass balance the simulations indicate that the paleohigh isolated in deep pelagic basin seem to be the best site for replacement pervasive dolomitization because the high amount of compaction fluids with respect to the paleohigh rock volume.
The combined use of basin simulator and RTM has proven to be a powerful methodology that helps in verifying the model reliability and provides insights on the volumetric distribution of the diagenetic products.
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