Deformation processes in the Britannia Field, UKCS

The intensity and distribution of deformation within cores recovered from 2 4 Britannia Field wells has been quantified and used to assess the sub-seis mic deformation present. Structural logging has been amalgamated with micro structural and petrophysical analysis of fault rocks and the results used t o construct models of the fluid flow behaviour of fault zones and to evalua te the correlations between core-scale structures and the larger-scale seis mically mapped fault arrays. Deformation within Britannia is controlled pri marily by (1) early sediment disruption, dewatering, detachment and folding in semi-lithified sediments and (2) more long-lived clustered arrays of sm all faults developed within fault damage zones. Fault population analysis i llustrates that seismic-based mapping alone does not provide a good platfor m for accurately predicting the number of sub-seismic faults present. Analy sis of the effect of deformation features on fluid communication highlights the importance of small-scale faults in enhancing communication in complex and initially separate sand bodies.