A 3D photogrammetric study of Faroese cliff sections.

There are many exploration challenges associated with intra-volcanic plays, such as the well-documented seismic imaging problem. A Sindri-financed 3D photogrammetric study of seismic-scale cliff sections of the Faroe Islands was done in order to characterize reservoir architectures, connectivity and compartmentalisation of interlava clastic beds as an analogue for intra-volcanic discoveries, e.g. in the submerged Faroe-Shetland Basin. The inaccessible cliffs provide excellent vertical exposure through the lava field, but also laterally over many kilometres. Focus was on cliff sections composed of the Eocene Enni Formation, which is dominated by a mixture of simple and compound lava flows commonly separated by minor volcaniclastic beds, including the widespread Argir Beds. High-resolution digital photographs were taken out of the open door of a Bell 412 helicopter hired from Atlantic Airways in May 2010. The photographs were taken with GPS coordinates with a 60-80% overlap and were subsequently analysed at the GEUS Photogrammetry Laboratory by using a 3D stereo-plotter coupled with stereo-mirror technology. The method allows the quantification of geological data from the oblique photographs with a relative resolution down to decimetre scale while having a three-dimensional overview of the outcrops. Mapped features are stored in a GIS database and 3D polylines can be exported as shape files suitable for 3D modelling using, for example, Petrel reservoir engineering software. Moreover, by using ArcGIS, the 3D polylines can be projected onto 2D profiles in order to generate geological cross-sections. Furthermore, virtual videos can be compiled from the oblique photographs in order to demonstrate lateral variations. The 3D photogrammetric analysis of the Faroese cliff sections record important information for the estimation of reservoir geometry, connectivity and compartmentalisation of intra-volcanic reservoirs. This includes, for example, the wedging out of lava flows over several kilometres and the corresponding merging of under- and overlying interlava units. The identification of major channels, up to 45 m deep and 180 m wide, filled with volcaniclastic conglomerates and/or lava flows has implications for the role of sedimentation across the lava field. The vertical connectivity of the interlava units is inferred by the presence of dykes, fractures and reverse faults.