Decision Driven Modelling Strategy

Reservoir modelling capability has grown significantly over the last twenty years and data fidelity has enabled ever-increasing detail for certain reservoir parameters. This has led to a modelling workflow in which a single complex and detailed full field model is typically the focus. Sub-surface modelling is however, carried out to underpin field development or reservoir management decisions and these often require the understanding of geology and fluid flow at a range of different scales and uncertainties. Another danger in full field modelling is the tendency to focus on a sub-set of the full range of uncertainty in the outcome of a development decision. This is aggravated by the requirement to construct, calibrate and validate large numbers of full field model realisations, which is time and resource consuming. Working with a large complex model additionally leads to a linear workflow in which there is often limited time to revisit modelling assumptions and evaluate their impact on the business decision at hand. A decision driven modelling strategy based on multiple models at different scales offers a flexible solution to these issues. A broader description of the uncertainties at each scale is facilitated by the ‘big loop’ approach in which the integrated model is described completely by a single set of the ‘model parameters’. The ranking of uncertainties and the identification of low, expectation and high decision outcomes is then an output of the model rather than an assumed input.