Significance of Fault Seal in Assessing Prospect Fill Scenarios - A Case Study from the Southern North Sea

A key factor in the appraisal of a discovery is to establish the full extent of the accumulation using prospect fill scenarios. Typically, only very simplistic fill scenarios are derived in which faults are assumed to be sealing at reservoir-reservoir juxtapositions. In areas of complex faulting, a simple approach can give rise to erroneous volume estimates. Ignoring faults with sealing potential can result in an underestimated prospect evaluation and potentially missed pay. A case study from the Sole Pit Basin, Southern North Sea is presented. The study area is characterised by NW/SE trending faults formed during Mid-Late Jurassic extension that are crossed by NNE trending faults and lineaments. Published methods to convert SGR at reservoir-reservoir juxtaposition to threshold pressure were used to predict maximum column heights supported at the reservoir-reservoir juxtaposition, trap fill and potential leak points out of the discovery. The case study illustrates the significantly improved prospect understanding resulting from a quantitative fault seal analysis. The ability to demonstrate an accurate predictive model helps reduce uncertainty and increase confidence in volumetric calculations, and improves the understanding of hydrocarbon distribution within the discovery. This enables a more targeted appraisal programme, with associated risk, cost and time reductions.