Summary Concepts for the relation between faults and folds in an extensional regime have revealed the importance of detailed mapping of fault zones, particularly in combined structural-stratigraphic traps. We show in a case study from the Australian North West Shelf that extensional fault zones are composed of several individual faults. Depending on the depth within the faulted interval, the individual faults may be interrupted by relay ramps. Additionally, release faults perpendicular to the main faults may introduce further potential breaches of the fault seal. Understanding the faults within the reservoir at this level of detail will assist in better understanding the fault seal risk for combined structural-stratigraphic traps.