Modelling Continental Margins

Charles Troy

Geophysicists at the Universityof Liverpool have developed a new twist on satellite imaging to help the oil and gas industry more precisely identify where the oceans and continents meet.

They have produced a mathematical technique to process satellite data that can map the thickness of the Earth’s crust under the oceans to locate where the continents meet oceanic crust. The technique has been used to measure the crustal thickness of areas such as the South Atlantic, the Gulf of Mexico and the Arctic to identify new areas for oil and gas reserves.

The continental crust is the layer of granitic, sedimentary and metamorphic rock that forms the continents. It is very thick, compared with oceanic crust, which forms part of the outermost shell of the planet. The transition between the continental and oceanic crusts, however, is difficult for scientists to identify because it lies far out to sea under thick sediment.

The area that separates the continental and oceanic crust, called a rifted continental margin, forms when continents start to break apart and new oceans are formed in between. Scientists have been investigating where and how these margins are formed to better understand the map of the world and, in particular, to identify where new oil and gas reserves may be found.

The new satellite remote sensing method relies on very small fluctuations in the strength of the Earth’s gravitational field, which occur as a result of the difference in thickness between the continental and oceanic crusts. Scientists can use these variations to predict the thickness of crust and to map the edge of the continental and the start of oceanic crust under the sea.

Professor Nick Kusznir, at the university’s department of Earth and ocean sciences, explains: “Understanding where rifted continental margins are located and how they form is important both for finding oil and gas reserves at continent-ocean margins and for territorial claims under the UN law of the sea process.

“As conventional oil and gas resources become progressively exhausted, our future supplies will have to come from sedimentary basins at rifted continental margins in very deep present-day waters. While deep-water oil and gas exploration at rifted continental margins is very expensive, it can produce enormous rewards, as illustrated by recent major oil and gas discoveries in offshore Brazil, Angola and the Gulf of Mexico.”