To define flow units in sedimentary sequences it is equally important to not only identify reservoir rocks that accommodate free flowing fluids, but also to recognise cap rocks that act as barriers to fluid movement. The recognition of good reservoirs and effective seals is critical not only for conventional and unconventional petroleum reservoirs, but also in prospective areas for subsurface capture and storage. This presentation focuses on the association between bulk rock inorganic geochemical ICP-OES-MS (elemental) data acquired on cuttings and core, and the relationship between flow units in porous reservoir sediments and their accompanying cap rocks. The study utilises the open file (NOPIMS) data available from the Archer Formation reservoirs (including the Caley Sandstone) in the Bedout JV Dorado Field wells, located in the Roebuck Basin on the Northwest Shelf. 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 very good, good, moderate, poor, and very poor flow. A statistical approach is employed to establish elemental associations for discrete flow zones. The advantage of this workflow 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 can potentially be used to identify pressure ramp ups in overburden sediments.
O'Neill et al. (Sun,) studied this question.