Characterization of fault zones in the Gullfaks Field for reservoir modelling

Abstract

A fault-seal study has been performed for faults around the A platform of the Gullfaks Field, Northern North Sea. The operator’s depth grids and isochore maps were used to build a FAPS database. Together with petrophysical logs, these data were used to compute the distribution of shale gouge ratio (SGR: fault-zone % shale) over each fault surface.Pressure data from exploration and production wells have been projected onto the modelled fault surfaces. Where well data permit, across-fault pressure drops at particular time instants during production are displayed. These dynamic pressure drops provide a guide to the permeability of the fault zones once flow has started.The calculated fault parameters (throw and SGR) can be converted to other parameters such as fault-zone thickness and permeability. These can be used to derive fault transmissibility modifiers for reservoir simulations. The calculated properties are compatible with the recorded pressure history and tracer movement between wells.