This work presents a new open-source carbonate reservoir case study, the COSTA model, that uniquely considers significant uncertainties inherent to carbonate reservoirs, providing a far more challenging and realistic benchmarking test for a range of geo-energy applications. The COSTA field is large, with many wells and large associated volumes. The dataset embeds many interacting geological and petrophysical uncertainties in an ensemble of model concepts with realistic geological and model complexity levels and varying production profiles. The resulting number of different models and long run times creates a more demanding computational challenge than current benchmarking models. The COSTA model takes inspiration from the shelf-to-basin geological setting of the Upper Kharaib Member (Early Cretaceous), one of the most prolific aggradational parasequence carbonate formations sets in the world. The dataset is based on 43 wells and the corresponding fully anonymised data from the northeastern part of the Rub Al Khali basin, a sub-basin of the wider Arabian Basin. Our model encapsulates the large-scale geological setting and reservoir heterogeneities found across the shelf-to-basin profile, into one single model, for geological modelling and reservoir simulation studies. The result of this research is a semi-synthetic but geologically realistic suite of carbonate reservoir models that capture a wide range of geological, petrophysical, and geomodelling uncertainties and that can be history-matched against an undisclosed, synthetic ‘truth case’. The models and dataset are made available as open-source to analyse several issues related to testing new numerical algorithms for geological modelling, uncertainty quantification, reservoir simulation, history matching, optimization and machine learning.

There are a number of benchmark studies for clastic reservoirs (e.g. the PUNQ, SPE10, Brugge Field, Watt Field, or Norne Field models) for challenges such as EOR, testing new numerical algorithms for reservoir simulation and uncertainty quantification. To date, the only carbonate benchmark reservoir is UNISIM-11-D which focuses on the Brazilian Pre-Salt however, neglects any geological uncertainties. This paper presents an update on ongoing work to create an open access reservoir model ensemble that considers the major ranges of interpretational uncertainties inherent to carbonate reservoirs covering interpretational scenarios and modelling choices such as geomodelling techniques. The result of this research is a semi-synthetic but geologically realistic suite of carbonate reservoir models that capture a wide range of geological, petrophysical, and geomodelling uncertainties and can be history-matched against a synthetic “truth case”. Eventually the models will be made available as open access data to provide the opportunity for reproducible science in the field of reservoir simulation and help training new generations of reservoir engineers in the art of simulating and history matching carbonate reservoirs over the next decade.