A workflow for modelling fault leakage probability in the Gullfaks field

Allan maps are a convenient way of displaying juxtaposition of reservoir and seal facies along faults to help estimate where, and how much, fluids such as hydrocarbons, water or CO2 can leak through faults. In this paper, we generate Allan maps automatically for seven major faults of the Gullfaks field within a structural uncertainty modelling framework. We first perturb both fault and horizon geometry, always keeping the structural model consistent, and generate these juxtaposition maps for each realisation. The area of reservoir to reservoir and reservoir to seal facies is computed for each fault and can help rank and select relevant realisations for geological property modelling and fluid flow simulation. Then, from a set of 20 realisations, we integrate the information from the Allan maps into volumic grids encompassing all geometric realisations of each fault and compute the probability that a fault is present and leaking in each cell of the grid. This representation is useful in itself to better understand the possible connections between fault blocks in the Gullfaks field, and to provide detailed transmissibility information to flow simulators.