Controls on the distribution of volcanism and intra-basaltic sediments in the Cambo-Rosebank region, west of Shetland

Abstract

The NE Atlantic margin is one of the last frontier areas of hydrocarbon exploration within the UK Continental Shelf. In 2004, a major oil and gas discovery (Rosebank) was made within Paleocene–Eocene-age lavas in the Faroe–Shetland Basin. The Rosebank Field consists of intra-basaltic terrestrial to marginal-marine reservoir sequences, separated by basaltic lava flows and volcaniclastics. Despite the identification of a major intra-lava-incised drainage system running parallel to the SW–NE-trending Rosebank Field, the controls on the distribution of both the volcanics and the intra-basaltic sediments were previously unclear, in part due to the difficulties that volcanic sequences pose to seismic acquisition, processing and interpretation. This has led to uncertainty in defining the wider intra-basaltic play. However, the examination of the recently acquired FSB 2011–12 MultiClient GeoStreamer® Survey has facilitated an increased definition of the geological units within and below the volcanic succession, and a reinterpretation of the Late Paleocene–Early Eocene stratigraphy. Through integration of 3D seismic data and well analysis, we present a regional overview of the volcanics and intra-basaltic sediments in the Rosebank region of the Faroe–Shetland Basin. We find that the structural setting of the Rosebank Field, in addition to lava-flow morphology, strongly influences the distribution of the intra-basaltic play fairway within the Paleocene–Eocene-aged Flett Formation. Restriction of fluvial siliciclastic sediments adjacent to the Corona Ridge extends the theorized Rosebank play fairway to the area SW of the Rosebank Field. Our analysis indicates that understanding the underlying basin structure is integral to the success of intra-basaltic plays.