An open access carbonate reservoir model

Abstract

This thesis presents a new open-source carbonate reservoir benchmarking case study, the COSTA model, that uniquely considers major uncertainties inherent to carbonate reservoirs, providing a far more challenging and realistic benchmarking test for a range of geo-energy applications. The COSTA model is large (1,600 km2 ), with many wells (447) and large associated hydrocarbon volumes (109 bbls). 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 large number of models and long-run times creates a harder computational challenge than older 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 to build the model uses 43 wells from fully anonymized published data from the north-eastern part of the Rub Al Khali basin, a sub-basin of the wider Arabian Basin. My model encapsulates both the large-scale geological setting and reservoir heterogeneities found across the shelf-tobasin profile (~36,000 km2 ), into one single model (~8,300 km2 ), 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 reservoir characterisation, uncertainty quantification, reservoir simulation, history matching, robust optimisation, and machine learning. The novelty of my work is the provision of a unique and realistic open-access dataset that enables reproducible science in the field of reservoir characterisation and simulation and offers new training opportunities in the areas of reservoir characterisation simulation and prediction of the reservoir performance of carbonate reservoirs. The model(s) can also be used to study geological sequestration of CO2, the feasibility of EOR processes, geothermal and groundwater studies.