Reaction Transport Modelling in the Prediction of Dolomitization Distribution

Application of Reaction Transport Modelling to case histories of dolomitization allows testing the genetic interpretation and may help in predicting the lateral extension of the dolomite bodies in hydrocarbon carbonate reservoir. Results of numerical diagenetic modelling simulations of four different conceptual dolomitization models are presented. The first case evaluates the compaction driven model in a drowned paleohigh (Jurassic, Southern Alps, Italy): the simulation indicates the ratio between the volume of fluids coming from the basin and the volume of the paleohigh as the main limiting constraint. Two synsedimentary dolomitization processes (thermal convection and mesohaline reflux) are tested on an isolated carbonate bank (Paleozoic, Kazakhstan). Thermal convection produces a dolomitized wedge in the bank margin area; reflux model proves that some dolomitization can be produced with mesohaline sea water influx from the top of the platform. Hydrothermal dolomitization was simulated in a shallow burial setting in presence of deep feeding faults (West Africa pre-salt) demonstrating the importance of faulting and fracturing in this dolomitization type. In all the considered cases the simulations suggest the hydrologic system as the most important driver for dolomitization: the final geometry of dolomite bodies is greatly affected by the permeability assumptions and presence of fractured zones.