Forward Modelling of Turbidite Sand Deposits on Restored Paleobathymetric Surfaces: Case Studies in Salt Tectonics Affected Areas

Anne Domzig¹, Stuart MacLean¹, Dave Waltham², Tim Rice¹, and Ryan Shackleton¹
¹Midland Valley Exploration Ltd., 144 W. George St., Glasgow G2 2HG, U.K.
²Department of Geology, Royal Holloway, University of London, Egham, Surrey TW20 0EX, U.K.

Paleoturbidite systems are sand-rich sediments and constitute common hydrocarbon plays in most offshore basins. They are often not easy to identify on the seismic, if no high-quality seismic attribute or isopach maps are available. Forward modelling of turbidity flows is then a good technique to estimate the location and shape of such deposits and especially the sand-rich areas, away from well constraints. The method presented here is using the Sediment Modelling module of the Move software which forward models turbidity flows and their depositional patterns. We show how the results depend on the restoration parameters but also on other factors such as tectonic structures shaping the seafloor and flow parameters.

Before modelling the palaeoturbidites, the present-day horizons have been sequentially backstripped and restored up to the time of deposition of the turbidites (Waltham et al., 2008, and this study). The goal of the sequential restoration is to remove step by step the effects of the sediment compaction and deformation (folding or faulting) of the sediments, in order to obtain the paleoseafloor on which the sands of interest have been deposited. We show the full workflow (Fig. 1) integrating both the 2D and 3D restoration and the turbidites forward modelling, using examples mimicking typical structures possibly found in salt tectonics affected areas, e.g., the Gulf of Mexico.

The first study area is a synthetic dataset where salt diapirism is predominant. The second dataset is located in the North Sea and is affected mainly by normal faulting. Wells were available only for the North Sea study area. The results of the 2D restoration are shown in Figure 2 (Fig. 2A, synthetic diapirs dataset; and Fig. 2B, North Sea dataset). Note that in Figure 2A the salt volume was not kept constant. The same workflow has then been applied to the 3D surfaces in order to obtain paleosurfaces for the base of the studied sands, which were then used to model turbidite deposit patterns at the time of the sand deposition.

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012