Combining Petrophysical and Seismic Data to Assess Source Rocks - A Case Study from the Upper Jurassic of the North Sea

Abstract

The organic-rich upper Jurassic Draupne and Heather Formations are the main proven source rocks of the Norwegian North Sea. We have developed a workflow for the organic geochemical, petrophysical, and seismic characterization of the Draupne and Heather Formation source rocks in a study area in the Viking Graben in the Norwegian North Sea. We characterized the vertical and lateral organic richness variations using biostratigraphy, organic geochemical data, and petrophysical logs. To map the TOC distribution using seismic, we performed detailed seismic interpretation and seismic attribute analysis following the petrophysical calibration of TOC with the VP∕VS ratio and P impedance on well data. Similar patterns of low-impedance high-TOC areas highlighted and mapped from the petrophysical studies were also observed on seismic relative acoustic impedance and amplitude maps. The post-stack seismic data conditioning (structurally orientated noise reduction) improved the quality of the input mega-merge seismic data and allowed the application of colored inversion, structural and fault imaging, as well as multi-attribute combination and visualization techniques, which have been efficient in highlighting the distribution of high-TOC areas within the study area.