Structural modelling and modelling of subsidence history in order to reconstruct and quantify the tectono-sedimentary evolution and the generation, migration and alteration of hydrocarbons offshore Norway.
Final Report Abstract
The main objective of this project was to get in depth understanding of the deformation processes at the Nonwegian passive continental margin and the influence on petroleum systems through time. The study areas were the SW Barents Sea and the Voring Margin. To evaluate the present state of the Voring Margin a crustal scale 3D structural model of the Voring and More basins, including the continental part and the oceanic part close to the continent transition, has been constructed and used as a base for structural analysis. Using gravity and temperature data as further constraints, the first order structures of the lithospheric mantle beneath the margin could be derived. Special highlights were (1) that, at the Voring Margin, the lithospheric manfie is less dense beneath the ocean than beneath the confinent, (2) that models integrafing the detailed knowledge ofthe crust as well as gravity and temperature data put strong constraints on the.geometric and thermal configurafion ofthe lithosphere-asthenosphere boundary and (3) some new insights into margin history. Results on the history of the margin were obtained from 2D structural reconstruction that has been used to quantify the brittle extension that has affected the margin since the beginning of the Cretaceous. The outcome of this part of the study indicates that crustal stretching was differential for the upper and lower crust (decoupled system) and that the largest part of the post-Jurassic subsidence at the Nonwegian margin was not related to brittle deformation, but to deeper seated processes. Also structural analysis based on the 3D model showed that changing patterns of deformafion are relevant to understand the opening of the North Afiantic Ocean, but also the fate of petroleum systems in the area. Regional structural and subsidence analysis showed that the location of depocentres as well as paleo-depth changed repeatedly with time and that subsidence has a large load-induced component Thus, one implicafion of this study is that large quantities of sediments were supplied by erosion of the source area. A fourth main result was the quanfificafion of uplift-related changes in pressure temperature condifions and related phase changes in petroleum systems, in particular concerning the impact of glacial (un)loading in the SW Barents Sea. Modelling of a number of regional 2D lines in the south-western Barents Sea established the sensitivity of a petroleum system on the Arcfic borderiands of.the margin to uplift and erosion for three scenarios belonging to the Cenozoic era. These are Paleocene and Oligocene- Miocene inversions related to North Afiantic Rifting, and a Late Pliocene-Pleistocene inversion related to glacial cycles. The integral view on the processes controlling the evolufion of passive volcanic margins strongly profited of the good collaboration within the CRP and with other partners in EUROMARGINS. The assessment ofthe structural relafionships of different lithospheric levels is unique at the achieved spatial resolution and was only possible due to the joint expertise in geophysical and geological.methods with regional expertise and data.
