Print this pageA Revised Hypothesis for the Structural Evolution of the East Brae Region of the South Viking Graben, North Sea
BROWN, M. A., M. P. COWARD, P. ALLEN, and S. BUCKNER
Three Dimensional visualisation and modelling of the East Brae field, South Viking Graben, has allowed complete revision of the structural evolution of the area. The area is one of well documented inversion at the end Cretaceous. Initial 3D visualisation provides a much clearer picture of these structures than seismic interpretation packages.
The footwall of the South Viking Graben is kinked at the junction between the original extensional fault, the Western boundary Fault (WBF) and the erosion surface above. Fault bend folds are produced as the hanging wall moves over this kink during inversion. The forelimb dip of these folds indicates the amount of steepening which the WBF underwent during inversion. This fault has been rotated to its pre-inversion orientation and contoured providing valuable information about sources and directions of sediment input into the basin. Forward modelling using this rotated fault surface has reproduced the inversion structures which are clearly seen on the seismic sections. This forward modelling method allows an accurate and rapid assessment of the fault geometry, particularly at depth where seismic resolution is poor, and of the movement directions, displacement values, and shear vectors, necessary in the hanging wall.
This allowed revision of the basic model within the limits imposed by the original seismic data until an accurate hanging wall was modelled; these values were then applied to restoration of the real data set. Additional factors have been included in the forward modelling to study strain within the hanging wall to aid prediction of the geometry and density of fracture sets.