Transmissibility multipliers provide a simple way of accounting for the effects that faults have on fluid flow in production simulation models. Recent studies have shown that transmissibility multipliers can be quantified from parameters such as fault thickness and permeability (Knai and Knipe, 1998; Manzocchi et al., 1999). Generally, these latter parameters must be approximated using empirical relationships with some host rock properties such as V-shale or net-to-gross ratio as well as fault displacement magnitude (Manzocchi et al., 1999).
In this study, the effects of two different representations of faults on the history match and the predicted (simulated) seismic impedance are compared for the Pierce Field, North Sea. In the first case, fault transmissibilities were adjusted and the faults were extended in a trial and error manner to improve the match to fluid contacts and production history. In the second case, a step-by-step derivation of the fault transmissibilities in the Pierce Field was adopted based upon the integration of collected and upscaled properties of the deformed and undeformed reservoir as well as empirical relationships between fault offset and thickness. Historical production data were used to compare the effectiveness of the two methods. Furthermore, a synthetic seismic impedance response was generated from both simulation models, using a velocity model based on the Gassmann-Biot theory of elastic wave propagation in fluid saturated porous solid (Gassmann, 1951; Biot, 1956). This allows the assessment of different fault representations when trying to predict optimal times for further time-lapse seismic surveys. The results demonstrate the effectiveness of the derived transmissibilities model in generating a satisfactory history match in a relatively short time period. The generated seismic models show that, by acting as baffles/barriers to fluid flow, faults can play a major role in creating residual seismic features that can be observed on 4D seismic surverys. Incorporating realistic fault rock properties into the simulation model, which is used to create synthetic seismic, can therefore allow geophysicists and engineers to better plan the timing of 4D seismic surveys so that they have the greatest influence on field development decisions.