The fossiliferous Eocene carbonate reservoir interval of the offshore Hasdrubal Field has a diagenetic history in which dolomitisation of micrite-rich facies has significantly enhanced reservoir quality. Using published information on the diagenetic evolution, digital textural representations of the limestones and dolostones are created using the Multi-Component Architecture Method (MCAM). This technique allows integration of images at different length scales (e.g., SEM, micro-/nano- XRT) which provide different forms of information about the pre-dolomitisation rock, including textural and compositional factors, and the arrangements of preserved components. These digital representations of the dolostones, together with their now completely overprinted precursor micritic limestones, permit exploration of the impact on porosity and permeability of uncemented, partly cemented and biomoulds Nummulites, their number per unit volume, and their orientation (i.e., uniformly or randomly orientated) allowing investigation of the petrophysical consequences of different distributions, orientations and abundances of the matrix and fossiliferous components. Viable diagenetic pathways, which were identified by thin section analysis as well as data available in the literature, are linked to petrophysical property evolution. In this way MCAM permits investigation of earlier stages of the diagenetic processes which were overprinted by later diagenetic processes. ... Read more

The Eocene El Garia Formation in the offshore Hasdrubal Field was originally a nummulitic limestone in which subsequent burial dolomitization has significantly enhanced permeability. Identification of the reservoir's petrophysical property distributions requires knowledge of the spatial extent of its dolomitization, in turn requiring understanding of the processes that caused the dolomitization. Some of this understanding can be derived from measurements but others need to be simulated. In this study, the former are used as guides and we focus on the latter, evaluating the character of the dolomitizing fluid's movement and temperature patterns by using basin modelling to develop heat-flux simulations to represent the time of dolomitization. Basin modelling reconstructs the region's geology at the time of dolomitization, while heat-flux simulations recreate the appropriate conductive and convective heat and mass transport through these systems. Potential key drivers are rock mass and fault-zone permeability, and the position and shape of any salt domes. The results suggest that salt dome shape and position is the dominant control, the salt dome localizing convective systems which also use convenient faults so that hotter upwelling fluids pass through the Hasdrubal reservoir and are instrumental in the development of burial dolomitization. ... Read more