Combining basin modelling with high-resolution heat-flow simulations to investigate the key drivers for burial dolomitisation in an offshore carbonate reservoir

The Eocene El Garia Formation in the offshore Hasdrubal Field is a nummulitic limestone in which dolomitisation has significantly enhanced reservoir quality. The estimation of dolomitic reservoir properties requires knowledge of the spatial extent of the dolomitisation in the field, which can be supported by understanding the processes that have caused dolomitisation. Hence, in this study we evaluated flow patterns that could have caused dolomitisation and identify the key parameters that could have controlled them by combining basin modelling with high-resolution heat-flow simulations.
Basin modelling allowed reconstruction of the basin geometry at the time of dolomitisation while the heat-flow simulations enabled modelling of the advective and conductive heat transport through these geometries. Simulation results were compared to existing δ18O and fluid inclusion data to assess the different flow scenarios and identify key flow drivers. These include rock and fault zone permeability and the dimension and location of an underlying salt dome.
Our results suggest that it was salt dome position that had the biggest impact on flow pattern and hence is a key control for dolomitisation. The presence of a salt dome causes significant convection with upwelling of hot, and downwelling of cold, fluids around the fault zones.