234
A. NELSON-SMITH
gal (95 000 litres) per day, this fissure was also plugged, whereupon a
further leak appeared flowing at up to 4 000 gal (18 000 litres) per day.
The problems of dealing with a leakage under pressure in 190 ft (57 m)
of water are considerable; 100 days after the blow-out it was estimated
that a total of 3: million gal (nearly 15 million litres) had been lostover a tenth of the cargo of the '' Torrey Canyon"-within
a much
smaller area (Smithsonian Institution, 1969a, b ; Jones et ab., 1969;
Standley et al., 1969). Oil was still flowing at the end of July 1969 and
fresh leaks were reported in January 1970. I n a recent American study
quoted by Batelle-Northwest (1967) it was estimated that a minimum
of 300 000 gal (1 300 000 litres) might be lost during the six weeks
required to regain control of a typical GuIf Coast off-shore well. The
upper limit of the estimate was, however, set at nearly four times the
volume of " Torrey Canyon's " cargo.
111. PROPERTIES OF PETROLEUM OILS
A. Physico-chemical characteristics
Serious problems of pollution are caused by the crude oils, residual
fuel-oils, lubricating oils and miscellaneous tank washings, sludges and
tars-known collectively as " persistent oils " (Ministry of Transport,
1953) to distinguish them from light fuel oils such as gasoline (motor
spirit), kerosine and gas oil which spread and evaporate very rapidly
when spilt.
Crude oils are by far the most complex and variable of these persistent oils. A general review of their composition and properties is
given by McKee (1956) and some typical values of important characteristics of crude oils entering European waters are listed by Berridge et
al. (1968a) and Brunnock et al. (1968). When fresh, they have relative
densities in the range 0.829-0-896, although evaporation of the lowboiling " light ends " quickly increases this to 0.921-0.975 for an
" atmospheric residue " boiling above 370"C, or t o 1.023-1.027 for a
Middle East crude residue boiling above 1000°C (the density of sea
water being 1.025). Smith (1968) gives a table showing the loss of bulk
and gain in density of Kuwait crude oil as progressively higher-boiling
fractions evaporate from it, reproduced as Table I .
The '' pour-point "-an imprecise value giving some indication of
whether an oil will spread or solidify on a cold surface-varies from
7°C (Brega, Libya) to minus 34OC (Tiajuana, Venezuela). The Libyan
oil has 11.4% wax against 4.8% in the Venezuelan; Middle East crudes
contain 5.5-7.0y0 wax and their pour-points are also intermediate.
Kinematic viscosity (measured at 38OC) is fairly uniform for these
A. NELSON-SMITH
gal (95 000 litres) per day, this fissure was also plugged, whereupon a
further leak appeared flowing at up to 4 000 gal (18 000 litres) per day.
The problems of dealing with a leakage under pressure in 190 ft (57 m)
of water are considerable; 100 days after the blow-out it was estimated
that a total of 3: million gal (nearly 15 million litres) had been lostover a tenth of the cargo of the '' Torrey Canyon"-within
a much
smaller area (Smithsonian Institution, 1969a, b ; Jones et ab., 1969;
Standley et al., 1969). Oil was still flowing at the end of July 1969 and
fresh leaks were reported in January 1970. I n a recent American study
quoted by Batelle-Northwest (1967) it was estimated that a minimum
of 300 000 gal (1 300 000 litres) might be lost during the six weeks
required to regain control of a typical GuIf Coast off-shore well. The
upper limit of the estimate was, however, set at nearly four times the
volume of " Torrey Canyon's " cargo.
111. PROPERTIES OF PETROLEUM OILS
A. Physico-chemical characteristics
Serious problems of pollution are caused by the crude oils, residual
fuel-oils, lubricating oils and miscellaneous tank washings, sludges and
tars-known collectively as " persistent oils " (Ministry of Transport,
1953) to distinguish them from light fuel oils such as gasoline (motor
spirit), kerosine and gas oil which spread and evaporate very rapidly
when spilt.
Crude oils are by far the most complex and variable of these persistent oils. A general review of their composition and properties is
given by McKee (1956) and some typical values of important characteristics of crude oils entering European waters are listed by Berridge et
al. (1968a) and Brunnock et al. (1968). When fresh, they have relative
densities in the range 0.829-0-896, although evaporation of the lowboiling " light ends " quickly increases this to 0.921-0.975 for an
" atmospheric residue " boiling above 370"C, or t o 1.023-1.027 for a
Middle East crude residue boiling above 1000°C (the density of sea
water being 1.025). Smith (1968) gives a table showing the loss of bulk
and gain in density of Kuwait crude oil as progressively higher-boiling
fractions evaporate from it, reproduced as Table I .
The '' pour-point "-an imprecise value giving some indication of
whether an oil will spread or solidify on a cold surface-varies from
7°C (Brega, Libya) to minus 34OC (Tiajuana, Venezuela). The Libyan
oil has 11.4% wax against 4.8% in the Venezuelan; Middle East crudes
contain 5.5-7.0y0 wax and their pour-points are also intermediate.
Kinematic viscosity (measured at 38OC) is fairly uniform for these