Reliance on oil and gas
Without natural gas, oil and coal, our world would stand still. Scarcely a car, a train or a ship would be seen. Computers would shut down and the lights would go out in most offices. Today’s industrial nations are almost entirely dependent on fossil fuels, and energy consumption around the world has risen by about 70 per cent over the past three decades. The International Energy Agency (IEA) in Paris estimates that consumption will increase by at least another 50 per cent by 2030. The greatest consumers are the USA, China and Russia, but here too the demand for energy will continue to escalate.
The growing demand and increasing prices can be expected to fuel interest in the oil and gas deposits buried deep in the oceans, previously considered too expensive to extract.
Formation and exploration of fossil fuels
Gas and oil form in the sea over a period of millions of years, as the remains of animals and plants sink to the ocean floor. Combined with particles flushed from the land, they are buried and compressed into layers of sediment several kilometres thick on the ocean floor. Aided by the Earth’s pressure and temperature conditions, bacteria convert the biomass into precursor substances from which hydrocarbons are ultimately formed. These hydrocarbons can permeate certain layers of rock and sediment as they move up towards the surface, in a process called migration. In some cases they become trapped in impermeable layers of rock, which is where the actual deposits are ultimately formed. Depending on the ambient conditions, oil or natural gas develops.
Today’s sources of fossil fuels are between 15 and 600 million years old. During this period the continental plates shifted, transforming oceans into landmasses, with the result that mineral deposits can be found both on land and at sea. Oil and gas are usually found where vast layers of sediment cover the ocean floor.
- These days seismic equipment is used to prospect for new reserves. This equipment generates sound waves which are reflected back from the layers of rock and sediment in the ground. From the sound waves geologists can estimate whether the layers could contain oil or natural gas. At sea the sound waves are generated by what is known as an airgun, which works with compressed air. The echoes reflected back are received via hydrophones on the ocean floor or the research vessel.
7.1 > Extraction costs of conventional oil by type and region according to IEA and Petrobras estimates (enhanced oil recovery = improved oil production in mature oil fields).
The future of oil lies in our oceans
Since industrial oil extraction began in the mid-19th century, 147 billion tonnes of oil have been pumped from reserves around the world – half of it during the past 20 years. In 2007 alone, oil consumption worldwide reached a total of about 3.9 billion tonnes. There is no doubt that extraction will soon be unable to keep pace with annually increasing needs. Experts anticipate that in the next 10 years so-called “peak oil” will be reached, the point at which the world’s oil supplies go into irreversible decline.
Currently the conventional oil reserves – i.e. those which can be recovered easily and affordably using today’s technology – are estimated to be a good 157 billion tonnes. Of this amount, 26 per cent (41 billion tonnes) are to be found in offshore areas. In 2007 1.4 billion tonnes of oil, the equivalent of about 37 per cent of annual oil production, was derived from the ocean. The proportion of offshore production is therefore already relatively high. The most productive areas are currently the North Sea and the Gulf of Mexico, the Atlantic Ocean off Brazil and West Africa, the Arabian Gulf and the seas off South East Asia.
- For some years now the trend has been towards drilling in deeper and deeper water. In 2007 oil was extracted from 157 fields at depths of more than 500 metres. In 2000 there were only 44 such fields. Of these, 91 per cent are situated in the so-called Golden Triangle in the Atlantic between the Gulf of Mexico, Brazil and West Africa. While the output of the relatively shallow waters of the North Sea (average depth 40 metres) will reduce in the coming years, production is likely to increase elsewhere, particularly in the Golden Triangle, off India, in the South China Sea and the Caspian Sea off Kazakhstan.
The deeper marine areas therefore harbour additional potential for the future. Experts estimate that the offshore trend will accelerate as oil becomes increasingly scarce. The downside here is that extraction is complex and expensive. For instance, extraction from fields at great depths requires floating production and drilling vessels, or pumping stations permanently mounted on the ocean bed. >