BP Exploration, London, has developed an aerial survey system that has enabled it to make faster decisions on new unexplored acreage in Indonesia and Ethiopia.

The airborne laser fluorosensor (ALF) provides a rapid and reliable indication of which offshore basins or areas are likely to contain oil by detecting offshore oil seeps.

BP said natural processes allow gas from subsea fields to break through the overlying rocks and rise to the sea surface, carrying with it traces of oil or condensate. The gas disperses into the atmosphere, but the oil remains as a slick that can extend several kilometers.

ALF relies on the tendency of oil to fluoresce under ultraviolet light. The system, carried on an aircraft, fires a laser that illuminates the sea surface with UV. Fluorescence is detected by a telescope and high efficiency sensors said to be about 1,000 times more sensitive than the human eye.

The returning light is separated into a spectrum, converted into electrical signals, and fed into a data logging computer system along with position information. By analyzing the spectra, BP can distinguish between light and heavy oils.

BP can distinguish permanent seeps from those suspected of having been caused by leaking tankers by carrying out a second survey after an interval. Slicks can be identified quickly because the fluorescent components of oil dissipate quickly in the open sea, BP said.

The company developed ALF at its research laboratories in Sunbury, near London, at a cost of about 2 million. It ran prototype tests off California and in the Gulf of Mexico.

The company installed systems in two Fokker F-27 Friendship aircraft. The planes, by making a series of parallel passes at an altitude of about 90 m, can together survey about 300,000 sq km/year of ocean.

The aircraft and equipment cost about 14 million plus 17 million/year operating costs.

BP said that amount is less than the cost of drilling two evaluation wells, which would provide an evaluation of only about 2,000 sq km.

BP has used the system off Indonesia, Ethiopia, and northwestern Australia. It now plans to turn its attention to the Black Sea, where it will explore for oil in collaboration with Turkiye Petrolleri Anonim Ortakligi, the Turkish oil company (OGJ, May 27, p. 112).

It also plans to use the system on a program in the South Carigolan contract area off Colombia's northwest coast (OGJ, June 3, P. 48).

BP estimates that during a 5 year program the aircraft will be capable of surveying many of the world's offshore frontier basins at a cost less than 1% of the company's investment budget.

Copyright 1991 Oil & Gas Journal. All Rights Reserved.

BP PUTS AIRBORNE LASER FLUOROSENSOR TO WORK

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