Significant volumes of heavy oil are still present in fractured carbonate reservoirs worldwide. Some of these reservoirs are good candidates for the application of thermally assisted gas- oil-gravity-drainage (TA-GOGD), a novel EOR technique. Unlike a normal steam flood, the steam is used as a heating agent only to enhance the existing drive mechanisms. The elegance of TA-GOGD is that the fracture network is both used for the distribution of steam (heat) and the recovery of the oil. The number of wells can therefore be kept to a minimum compared to conventional steam floods. Following encouraging pilot results in a field in Oman, a steam injection project is heading for implementation, a first of its kind on this scale. Studies to date indicate that recovery factors of 25-50% with Oil-Steam-Ratios of 0.2 - 0.4 m~3/ton of steam are feasible. The success of the project is critically dependent on the field-wide presence of conductive fractures and the ability to characterize them. Both stochastic and deterministic studies were tried, but the latter method is now favoured as it allows the use of geological and dynamic understanding as input to the modelling and honours existing faults, deformation mechanism and the conceptual model. Fracture characterisation is to some extent still an art and outputs are "only static scenarios". Therefore results should be validated with dynamic data as much as possible. The dynamic models are fully compositional, thermal and dual permeability, a complexity that is rarely encountered. Explicit fracture block models are used to verify that the heating rate and GOGD are captured properly, in particular for irregularly shaped fracture patterns. A new fully integrated workflow of fracture characterisation with static and dynamic modelling will enable to manage uncertainties and risks in a scenario based approach.
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