OMNIS (Offshore Mid-Norway: Integrated Margin and Basin Studies)

OMNIS has focused on fundamental geological processes linked to the formation and evolution of the Vøring and Møre margins offshore mid-Norway, with special emphasis on the deep sedimentary basins which have a long and complicated geological history. Through this we have addressed several of the most important challenges related to petroleum exploration at the mid-Norwegian continental shelf and margin, and our results can be used to reduce exploration risk. We have also focused on outer parts of the margin where volcanic activity related to breakup and initial seafloor spreading in the Norwegian-Greenland Sea was widespread and voluminous. To establish a good regional geological understanding the study area at the Norwegian margin has to be linked to a larger plate tectonic and paleogeographic framework. The most important results achieved in OMNIS can be summarized as follows: Continental breakup and initial seafloor spreading in the Norwegian-Greenland Sea (part of the NE Atlantic) were characterized by significant volcanic activity. The distribution of magmatic (igneous) rocks, both lavas extruded at the surface and intrusives which cooled and solidified at various depth in the subsurface, are mapped in detail based on an updated and much better seismic database. The seismic data are tied to the relatively few boreholes that exist at the outer margin. The main focus has been on the Norwegian margin, but we have integrated new results from corresponding mapping of other margins in the NE Atlantic. Through a closer integration of new seismic reflection data with existing deep seismic refraction data, we have carried out a comprehensive mapping of structures in the lower crust. Different models exist for these that have different implications for the margin evolution, and we would like to increase the understanding of their nature. The results of these studies are presented on a number of international conferences and they are/will be written up in 3 different papers with different thematic focus. Furthermore, we have recently published a new paper (in the well acknowledged journal "Geology") that compares the relative young Vøring Margin (ca 55 million years old) with a much older (ca 600 million years old), but similar volcanic margin, which now is located in the highest mountains of northern Sweden. By analyzing structures and composition of the rocks that can be studied in detail in outcrops in Sweden, we learn a lot that can be used to increase our understanding of what is deeply buried at the present margin offshore mid-Norway. In the deep sedimentary basins at the mid-Norwegian margin (in particular the Vøring Basin), new boreholes have provided new and important information on the deep Cretaceous stratigraphy of the outer Vøring Margin. Based on this, and a significantly improved seismic database, we have carried out a new regional mapping that provides important knowledge on the Vøring Basin evolution. This area has gone through a number of tectonic phases covering a long time span (> 300 mill. years), and we can now better understand the effects of these in both time and space. Based on analyses of deep seismic data, integrated with gravity and magnetic data, we have constructed several regional crustal transects across both the Møre and Vøring margins. These profiles form the basis for tectonic modelling. Through numerical modelling we want to improve our understanding of the processes that governs the basin development (e.g. vertical motions and temperature histories). This provides important knowledge for those exploring for hydrocarbons in this area. Existing regional transects from previous projects (e.g. EUROMARGINS and VØTEC) are also updated so that we can build further on earlier mapping and modelling studies of the Vøring Margin. Results from these studies are presented at international conferences and are now written up for publication. Results from OMNIS are also used to make improved plate tectonic and paleogeographic reconstructions of the regional geological evolution within the North Atlantic-Arctic region. An important contribution to improved models comes from our estimates of the stretching that has occurred intra-plate associated with the formation and evolution of sedimentary basins prior to the final continental breakup. This stretching has to be restored in our reconstructions, and this is now done much more accurate than in earlier published models. We have also carried out detailed studies of selected areas based on master student theses work. Some of their results have been further tested and compared to structural analogue models.

OMNIS is a strongly integrated project utilizing geological and geophysical data in a complete basin analysis, taking into consideration the plate tectonic framework, the lithospheric strength profile and architecture, the basin configuration and geometry , the far-field and local stress systems and the behaviour of the basin fill. This will provide the basis for analysing and modelling the thermal history and basin fluid flow and thereby provide new data on the petroleum systems. The project is subdivided into five work packages (WP1-5) covering all these aspects from the regional and large-scale tectonic framework (WP1), the formation and development of the basin itself and the influence of the deep structural grain (WP2) and the nature and influence of the magmatism associated with continental breakup (WP3). To achieve this, observations acquired through use of new and state-of-the-art data and tools (potential field, reflection seismic and well data) will be utilized and provide the background for nume rical and analogue modelling (WP4). Great attention will be paid to the integration of all data types and close interaction between the project working groups (WP5). It is the intention of the project group to provide new understanding of crucial mechani sms of basin initiation and development in passive margins and to study the interaction of these mechanisms. To achieve this the lithospheric strength profile and the lithospheric architecture must be constrained beyond the present knowledge. Furthermore, the relations between the different phases of extension in time and space as well as the amount of extension for each phase need to be better constrained, representing one of the most difficult tasks of the project. Finally, the heat sources affiliated w ith crustal thinning and magmatic activity need to be identified. The latter can only be evaluated by the use of modelling methods and verification against observations.