The sealing potential of volcanic rocks in hydrocarbon systems: A case study from the Rosebank Field

• Main Author: RAITHATHA, BANSRI,GITESH
• Format: Thesis
• Language: unknown
• Published: 2017
• Subjects: Rosebank; FMI; Image Logs; Volcanic; intra-volcanic; Faroe Islands; North Atlantic
• Online Access: http://etheses.dur.ac.uk/11978/; http://etheses.dur.ac.uk/11978/1/BANSRI_RAITHATHA_THESIS.pdf; http://etheses.dur.ac.uk/11978/2/Rosebank_Elastic_Rock_Properties_BR.xlsx

Hydrocarbon exploration in frontier regions has resulted in a series of discoveries within intra- and sub-volcanic basins along the NE Atlantic margin. The majority of these basins are blanketed by varying thicknesses of subaerial lavas and volcaniclastic sequences that form the Paleogene-aged North Atlantic Igneous Province. During Exploratory drilling in 2004, the 213/27-1Z well encountered two oil and gas accumulation with a total pay thickness of 52 metres, within the Late Palaeocene-Early Eocene aged Colsay Member sandstones within the Rosebank Field. These hydrocarbon-bearing reservoir intervals comprise numerous fluvial clastic sequences that are inter-layered between sub-aerially erupted basaltic lavas and volcaniclastic sediments. This discovery gave rise to a new hydrocarbon play concept. In this study, the sealing potential of the volcanic and volcaniclastic sequences is investigated using multi-scale subsurface datasets (with a particular emphasis on the value of high resolution borehole image logs; FMI) and field analogues from the Faroe Islands. Through the combined use of wireline logs (Bivariate cross-plots) and high resolution FMI images, the volcanic and volcaniclastic rocks in the Rosebank Volcanic Formations (RVFs) were characterised, and a detailed volcanic stratigraphic section of the RVFs was constructed, to understand how these lithologies vary vertically and laterally between wells. Bivariate cross-plots (photoelectric factor versus bulk density) indicates that there are two distinct compositions of lava flows: (a) Lava Type I is characteristic of the Rosebank Lower Volcanics, and has a higher Iron/Magnesium variety, suggesting that it was emplaced during the initial phase of volcanism; and, (b) Lava Type II is characteristic in the Upper and Lower Rosebank Middle Volcanics (RMV_U and RMV_L) and the Rosebank Upper Volcanics, and is depleted in Iron and Magnesium. The FMI images revealed that the RVFs comprise a diverse and complex suite of volcanic and volcaniclastic rocks (e.g. pillow ...