Sand injectites in the northern North Sea Basin

Abstract

Subsurface sediment remobilization and injection processes are important component of processes which occur in sedimentary basins worldwide. These processes are largely associated with deep-water clastic systems and have significant impact on the morphology and distribution of deep-water sand reservoirs which in turn have important implications for hydrocarbon exploration and production, and for carbon sequestration in deep-water clastic reservoirs. This research uses an integration of high-resolution 3D seismic data and well data from the Norwegian sector of the northern North Sea Basin to investigate the occurrence of large-scale sandstone intrusions or sand injectites in the Paleogene succession, to unravel their origin and mechanisms responsible for their development, distribution and associated complex geometries. The observations and interpretation from this study are documented in five result chapters (Chp. 3 – 7) which begins with a short overview of the hydrocarbon reserves/resource distribution of sand injectite fields in the UK and Norwegian sectors of the North Sea with the view to show that sand injectites form attractive exploration targets based on experience from North Sea oil/gas fields. This is followed by Chapter 4, which investigates the occurrence of discordant high amplitude anomalies within the Paleogene interval, which based on well calibration are interpreted as the seismic expression for large-scale sandstone intrusions within multiple stratigraphic intervals. Then, Chapter 5 documents for the ‘first time’ the occurrence of a Middle – Late Oligocene sand-rich deep-water depositional system modified by subsurface sediment remobilization and injection processes in the eastern part of the study area. The study highlights and describes the seismic expression of sand intrusion complexes developed in association with the depositional system and the implication of such intrusion complexes in deep-water settings. The succeeding Chapter 6 revisits aspects of the model and interpretation for the Late Cenozoic geological evolution of the northern North Sea presented by Løseth et al. (2013) with special emphasis on their proposed source for Oligocene sandstone and the processes responsible for the mounded shape of the Top Hordaland Group Unconformity. The findings based on available data demonstrate that their model for a strictly injected Oligocene sand is inconsistent with our observation. Lastly, Chapter 7 explores the various kind of interaction which exist between sandstone intrusions and polygonal fault systems present within their low-permeable host mudstone succession and how their co-existence may have aided sand injection or controlled the simple to complex geometries of the intrusions. Understanding the processes responsible for sand remobilization and injection is crucial to understanding the dynamics of a sedimentary basin’s evolution. The findings and interpretation presented here contribute to a clearer understanding of some of the factors and processes which favor the development of sand intrusions in the northern North Sea Basin. It also demonstrates the impact of post-depositional processes on deep-water systems because they can impact the distribution and geometries of reservoir units as well as the efficiency of fluid flow and migration through sedimentary successions over long periods.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Hodgetts (Supervisor) & Mads Huuse (Supervisor)