Geochemical characterisation of reservoir and seal sediments and free fluid flow using examples from the Dorado Field, Bedout Sub-Basin

The characterisation of flow units within sedimentary sequences is not only important for the identification of reservoir rocks that accommodate free-flowing fluids but also cap rocks that act as barriers to fluid movement. This is critical knowledge in both conventional petroleum-related settings and also prospective areas for alternative energies, such as carbon capture. This paper examines the association between inorganic geochemical (elemental) data acquired on cuttings and core, and the relationship between flow units in porous reservoir sediments and their accompanying cap rocks. Using conventional log data, core analyses, and elemental data, a free fluid model is developed over sections of reservoir and cap rock to establish zones of good, moderate, and poor flow. A statistical approach is then taken to establish elemental associations with each flow zone. The advantage of such an approach is that when a model has been defined for a field or basin, the acquisition of elemental data acquired during drilling can be used as a screening tool for both reservoir and cap rock identification. The elemental data could also potentially be used to identify pressure ramp ups in overburden sediments.