Unlocking the history of the North Sea to enhance future developments

Breakthrough research released from Universities of Aberdeen, Manchester, Sheffield and Queen’s University Belfast, Apache North Sea Ltd., RPS Ichron, Mærsk Olie og Gas and Lloyd’s Register reveals British Isles buried under ice sheets from 2.5 million years ago, a million years earlier than previously thought.

Francis Buckley, Principal Geologist at Lloyd’s Register talks about his involvement in this research and what this significant finding means for our understanding of past glaciation in North West Europe and future developments.

Breakthrough research

Extensive ice sheets are known to have repeatedly covered much of the UK and Ireland and these sometimes extended across the North Sea. Up to now, the scientific consensus has been that glaciation on this scale first occurred in the North Sea about 1.1 million years ago, but the new research has shown ice-sheets from Britain and Scandinavia coalescing in the North Sea from the start of the Quaternary period about 2.5 million years ago.

Back then the North Sea, was narrower and deeper than it is today, like a large ‘fjord’. Periodically, the ice sheets from the British Isles and Scandinavia advanced into water depths of around 250 m and generated icebergs nearly 300 m high. By 1.9 million years ago the two ice sheets repeatedly merged in the centre of the North Sea, filling the ‘fjord’, as they advanced and retreated in response to climate changes controlled by slight irregularities in the Earth’s orbit.

By obtaining sediment core samples from beneath the North Sea at a depth where they are rarely obtained and combing this with a range of geophysical datasets, a full analysis of Quaternary geology from deep beneath the North Sea could be carried out. This allowed for investigation in unprecedented detail of the ancient environments, preserved up to a kilometre below the modern seafloor.

Background to the research

My interest originally stemmed from research I was carrying out into Central North Sea Pleistocene geology while interpreting site survey and exploration seismic data for North Sea drilling operations. The traditional model of North Sea glaciation was apparently contradicted by evidence from the seismic data and I therefore assembled a composite interpretation of several seismic datasets which showed an Early Pleistocene glaciation to have extended across the Central North Sea.*

In 2013 I joined a research programme being conducted by members of University of Aberdeen in collaboration with Apache Corporation who were investigating a Central North Sea shallow gas reservoir to power offshore production facilities, (the Aviat prospect).

Shallow gas is generally considered to be a hazard to drilling, but the research programme was hoping to show that these shallow reservoirs could successfully be exploited. Core data acquired from the reservoir by Apache, then analysed and dated by members of the project proved the existence of an Early Pleistocene glaciation. The Aviat reservoir was subsequently sanctioned for full production.

The research project expanded by the addition of personnel from the University of Manchester, the British Geological Survey and several other academic and commercial institutions, all with an interest and experience in glaciogenic hydrocarbon reservoirs, petroleum geology of the North Sea in general and the Quaternary development of the Southern and Central North Sea basins.

What does this mean for future developments in the region?

Through this research the offshore site survey industry can now reference a more reliable model of North Sea Pleistocene geology, most of the previous work having been published in the 1990s. The commercial value of shallow gas reservoir in glaciogenic deposits has been proven and several other potential shallow reservoirs have already been identified, including the Peon prospect in the Norwegian North Sea. The North Sea Pleistocene can also provide a useful analogue for more ancient glaciogenic reservoir research and development, with features seen on North Sea seismic data also being identified in rock outcrops from glaciogenic reservoirs in North Africa, the Middle East and Australia. Repeated glacial loading of relatively shallow reservoirs, such as has occurred over oil prospects in the Danish North Sea, has been shown to induce hydrocarbon migration into much shallower geological formations than would otherwise have been possible.

Oil and Gas Authority mapping project.

A by-product of the project has been the production of the first reliable map of basal Quaternary palaeo-geography of the North Sea basin. This has been incorporated into the OGA prospect mapping project being carried out by LR. The project forms part of the OGA’s wider goal to maximise economic value of the UKCS, and develop how better understanding of the North Sea could lead to new discoveries.

A better understanding of Quaternary glaciations may also help inform future climate-change studies. Climate change is a defining factor of our time, and is ever more prevalent than before. However, a better understanding of geological records can reveal abundant evidence of the way Earth’s climate has changed in the past, and therefore may contribute to our understanding of how it may change in the future.

* The results were published by the EAGE in 2010 and the Geological Society in 2012