Hydrothermal dolomitization is one of the most important processes in enhancing or degrading carbonate porosity and permeability. This type of dolomite forms due to the circulation and/or mixing of different types of solutions, mainly seawater-derived or deep brines. The Lower Cretaceous Benicassim dolomitized ramp is an excellent example to study and evaluate the impact of hydrothermal dolomitization on reservoir quality distribution. In this contribution, the possible magnesium sources for the Benicassim case study are evaluated, as well as the reactivity of different dolomitizing fluids at variable temperatures. The results show that dolomitization at Benicassim occurred due to the circulation of a high temperature (> 80°C) fluid that had its origin from evolved seawater that interacted with K-rich rocks, probably from the Paleozoic basement. Reactivity evaluation of four possible dolomitizing fluids, by means of geochemical modelling, reveals that evolved seawater can be considerably more reactive than high-salinity brines. Fluid mixing between seawater and saline brines at 100 °C does not seem to affect the volume of fluid required to dolomitize the whole rock, but it considerably alters the saturation index of calcite. The variation of saturation index is a strongly non-linear process when two fluids are mixed.
|Title of host publication||72nd European Association of Geoscientists and Engineers Conference and Exhibition 2010|
|Subtitle of host publication||A New Spring for Geoscience. Incorporating SPE EUROPEC 2010|
|Publisher||Society of Petroleum Engineers|
|Number of pages||5|
|Publication status||Published - 2010|