Reactive transport modelling applied to the prediction of the dolomitization distribution in carbonate hydrocarbon reservoirs

Abstract

Reactive transport modelling can be applied to dolomitization to test interpretations of the diagenetic process and to help predict the lateral extent of dolomite reservoirs. Here we report applications to four different cases of dolomitization. The first case simulates the compaction-driven flow model of a drowned palaeohigh and demonstrates that the main limiting constraint is the ratio between the volume of basinal fluids and the rock volume in the palaeohigh. In the second case, hydrothermal dolomitization was simulated in a shallow burial setting above deep-seated rift faults, and shows the importance fault geometry may have in constraining the geometry of the dolomitized body. In the third and fourth cases, two synsedimentary dolomitization processes, thermal convection and mesohaline reflux, were tested in modelling an isolated carbonate platform. Thermal convection produced a dolomitized wedge in the bank margin area, and reflux model simulation shows that some dolomitization can also be produced by mesohaline seawater influx from the top of the platform. In all cases, the simulations suggest that the hydrogeological system is the most important driver for dolomitization, and the final geometry of dolomite bodies is greatly affected by the permeability and the presence of fractures.