Quantifying Structural Uncertainty by Forward Modelling the Seismic Response of Realistic Fault Relay Geometries

Structural geometry is a key uncertainty in subsurface geological modelling. Precise fault-horizon intersections and fault linkage geometries are often difficult to resolve using seismic data due to effects such as amplitude deterioration and diffraction. This inevitably leads to a simplification of the structural model when compared to geometries observed in analogous outcrop datasets. Implications for trap integrity and reservoir compartmentalisation include that at the exploration scale segmented faults may only be resolvable as single structures, with any non-imaged relay zones being potential unrecognised leak points. Conversely, in production settings poor resolution of intra-reservoir faults may lead to an underestimate in the degree of fault linkage and associated compartmentalisation.

Here, we use seismic forward modelling techniques to generate synthetic seismic cubes for a range of extensional fault relay geometries, including from existing subsurface models, field outcrops and LIDAR datasets. The different structural geometries are populated with identical petrophysical properties and seismically forward modelled using a typical North Sea velocity model and survey design. This approach has allowed us to observe the seismic response of realistic geometries, and hence to quantify the degree of uncertainty, and the potential implications for hydrocarbon production, associated with modelling faults based upon their seismically resolvable geometry alone.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California