Fault Sealing Behaviour in Three North Sea Reservoirs Estimated from Petrophysical and Production Data

Although understanding their flow behaviour is imperative for successful reservoir development, seismically resolvable faults are rarely sampled by wells. Their properties must be extrapolated from imperfect analogues or inferred from dynamic data and numerical reservoir simulation. Published methods regard fault transmissibilities as unknown tuning parameters with consequently limited predictive capability; workflows have therefore been developed for uncertainty assessment and conditioning to dynamic data of geologically consistent fault properties. This paper focuses on their application to three North Sea cases in which simulation models were able to reproduce observed field behaviour using fault properties consistent with core data. In contrast to published correlations between depth and reduced fault permeability, the interpreted permeability in the shallowest field was approximately one order of magnitude lower than for the other two, deeper reservoirs. Within the calculated ranges for Shale Gouge Ratio, the interpreted fault permeability functions for all three fields are within the prior uncertainty range estimated from analogue core data and are consistent with published studies. These functions add significantly to the number of available curves calibrated to sub-surface pressure data and could therefore be of considerable use for prediction of fault behaviour in similar fields without production data.