The Formation of Enigmatic Craters Offshore Norway

Gordon W. Lawrence and Joe A. Cartwright
3D Lab, School of Earth, Ocean and Planetary Sciences, Cardiff University, Cardiff, United Kingdom

The Møre Basin offshore Norway is an important area of gas production in the North Sea and there has been much recent exploration activity due to the discovery of the Ormen Lange gas field. Some of the largest non-impact craters ever visualised by seismic data are found in the area of the Møre Basin. The formation of these craters is shrouded in mystery.

The craters are associated with an opaline-A to opaline-CT boundary. If the formation of these craters is linked to fluid flow from beneath then these craters would be some of the largest blow-out features ever described. The development of similar craters could pose a significant geo-hazard on this and other petroliferous continental margins to industry installations as well as potentially affecting reservoirs, and thus it is important to understand how they formed.

We use regional 2D and local 3D seismic reflection data to answer some key questions regarding the formation of these enigmatic craters. Are they all on the same stratigraphic level? How do the craters relate to underlying structure? What is the morphology of the craters? What is the relationship of the craters to the overlying mass movements that bury the craters? Were they ever exposed at the seabed, or did they form in the subsurface? When did these craters form?

Our preliminary results show that some of the craters are associated with underlying structural highs, and this supports the hypothesis that the formation of these craters is associated with fluid movement in the subsurface. The craters are buried by the first slides to occur in this area of the Norwegian margin, which suggests that the formation of these craters may be linked to the onset of slope instability in this area. All the indications point to these craters being the expression of an as yet undescribed but important process in sedimentary basins.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery