African hills guide search for deep sea oil and gas

By studying rock outcrops in South Africa researchers have developed models to guide deep sea oil exploration and maximise oil recovery.

We all know that one day – soon – our current oil reserves will run dry. The hunt for new reservoirs is fierce, but it is costly too. As new wells can cost around $100 million to drill, oil companies want smart search methods that keep down costs and find the most lucrative fields.

Professor Stephen Flint, Dr Rufus Brunt and their research team from the School of Earth, Atmospheric and Environmental Sciences are helping companies to improve the accuracy of deep sea oil exploration. Perhaps surprisingly, however, the team keep their feet firmly on dry land: the hilly, desert-like Karoo area of South Africa.

Professor Flint knows that the rocks beneath his feet once formed a deep ocean basin. They were forced upwards by movements of the tectonic plates to form the hilly ridges that he sees today.

“The Karoo hills may not contain oil,” he admits. “But a wealth of knowledge lies within their sandstone layers.”

It turns out that Karoo’s formations are very similar to sand bodies buried deep beneath the sea floor in many parts of the world today. So by studying the Karoo, oil companies can develop new methods for exploring the deep ocean basins of Australia, Brazil and the Gulf of Mexico where millions more barrels of oil still lie hidden.

“Even the latest technology can only produce fuzzy images of rocks that lie 5 km below the sea bed,” says Professor Flint. “Sand bodies thinner than 30 m and small features will be missed, but these features can can have a considerable effect on how oil is stored within reservoirs. To inform extraction oil companies need more detail – and this is where the Karoo comes in.”

The Slope 4 research project involves a team of researchers from The University of Manchester and the University of Leeds. Led by Professor Flint, they spend long periods in the Karoo to gather geological data which they use to build computer and conceptual models of the rock formations.  

“To overcome the geometric uncertainty of deep reservoir rocks oil companies are interested in the shape, size and distribution of sand bodies in similar rock successions,” explains Professor Flint. “We are studying one of the best exposed systems in the world. Our work is significant: all major oil companies across the globe hold an interest in the project.”

As well as locating new reservoirs the Slope 4 models will influence the location and design of oil wells. “At $100 million apiece, oil companies want to get it right first time,” Professor Flint points out. “If we know how sand bodies lie in the Karoo we can predict how they may have formed in other locations; this knowledge is invaluable to inform the planning of new wells.”

In the past oil companies could extract less than a quarter of the oil in a reservoir. Guided by Slope4, optimal positioning of wells could allow companies to recover closer to three-quarters of crude reserves from new fields. 

Project fact file

Name: Slope 4 Karoo Synthesis Project

Dates: October 2013 – October 2016

Funding: Global oil companies

Partners: The University of Leeds

Lead researchers: Prof Stephen FlintDr Rufus Brunt and Prof David Hodgson (Leeds). 

Research group: Basin Studies and Petroleum Geoscience

Research centre: Centre for Atmospheric Science

School: School of Earth, Atmospheric and Environmental Sciences

Our work is significant: all major oil companies across the globe hold an interest in the project

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