Impacts of Glaciation on Petroleum Systems Offshore Northwest Greenland

Abstract

Seismic investigations and 2D petroleum systems modelling were conducted across the Melville Bay glaciated margin, offshore northwest Greenland, to improve our understanding of the stratigraphy and structure, as well as the nature of the petroleum systems and the impacts of glaciation on them. The margin has experienced multiple episodes of shelf edge glaciation since ~2.7 Ma, leading to the erosion, transportation and re-deposition of vast amounts of sediment, isostatic compensation, and repeated ice loading and unloading on the shelf through glacial-interglacial cycles; processes that can cause extreme variations in the structure and subsurface conditions of sedimentary basins, and have likely significantly impacted any petroleum systems contained within. Extensive 2D and 3D seismic reflection datasets across large areas of the complex paleo-rift topography of the Melville Bay margin were analysed, identifying an extensive gas-charged submarine landslide mass transport deposit reservoir along the crest of the Melville Bay Ridge (MBR) rift structure. Hydrocarbon anomalies were mapped across the study area within the top 1-2 km of Cenozoic stratigraphy, providing the first inventory of shallow gas and gas hydrates on the northwestern part of the Greenland margin. Evidence for historical fluid migration was also identified and showed the influence of paleo-rift topography and multiple shelf edge glaciations. Seismic anomalies were identified during a 3D seismic geohazards assessment for IODP Proposal 909; providing a workflow for future scientific drilling proposals. 2D petroleum systems modelling tested the evolution of the petroleum system in Melville Bay and provide a novel method for modelling glacial erosion, sediment re-deposition and multiple cycles of ice loading on the shelf. The modelling results suggest viable petroleum systems exist in Melville Bay, including both thermogenic and biogenic hydrocarbons, and that glaciation had a significant influence on margin evolution, causing substantial variations in subsurface pressure, temperature and sediment compaction across the shelf. These changes significantly impacted the petroleum systems, influencing source rock maturation and promoting reservoir leakage and fluid re-migration to reservoirs or through the overburden. Gas hydrate stability was impacted by variable pressure and temperature conditions, potentially causing dissociation at the phase boundary, but hydrate deposits at the seabed are predicted to remain stable throughout both past glaciations and future scenarios of global warming due to the relatively large water depths. The additional knowledge provided by this thesis will help improve the success and limit the safety risks associated with scientific and applied drilling in this environmentally sensitive high latitude environment. The research also provides an important analogue for studies concerning the interaction of petroleum systems and climate change; providing critical insight into how near-surface hydrocarbons may respond to past and future climate and oceanic warming.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Jonathan Redfern (Supervisor) & Mads Huuse (Supervisor)