Juxtaposition Seal Vs. Fault Rock Seal

Juxtaposition seal is where reservoir is completely offset against non-reservoir (below left). if reservoir thickness is < throw, then our reservoir sands are self-juxtaposed, in which case we need to rely upon the fault properties (e.g., clay smear) to create a fault seal. The second case is often leaky. The presence of sub-seismic structure (below right) can also create communication pathways through our juxtaposition case interpretation, bottom left. Therefore, there is usually uncertainty in our interpretations and we should carry alternative cases such as the one below right.