Journal of Petroleum Geology, Vol.2, No.4, pp. 439-447, 1980
©Copyright 2000 Scientific Press, Ltd.
THE EVOLUTION OF THE DEAD SEA FLOATING ASPHALT BLOCKS:
SIMULATION BY PYROLYSIS
A. Bein and O. Amit*
*Oil Research Division, Geological Survey of Israel, 30
Malkhei Yisrael Street, Jerusalem, 95501, Israel.
Abstract
The asphalts found as floating blocks on the Dead Sea and
deep-seated in wells differ from all other asphalts of the area, mostly by their more
abundant and much better preserved n-alkanes. Since biodegradation was found to be the
main alteration process through which crude oil was altered into asphalts, such
well-preserved n-alkanes are unexpected. A hypothesis of secondary generation of these
alkanes was tested by pyrolysis simulation of asphalt at 300° C during periods ranging up
to 60 days. The abundance and distribution pattern of the n-alkanes in the simulated
asphalts after 14 days of heating resembles that of the floating asphalt blocks and that
found at a depth of 3,500 m. In addition to saturated hydrocarbons, aromatics and gases
were also formed at the expense of resins and asphaltenes. The H/C ratio was balanced by
the formation of pyrobitumen and by a gradual decrease of the H/C ratio in the residual
resins and asphaltenes. The gas formed contained about 60 to 80% methane with an isotopic
composition of -41 to 42%. The hydrocarbon content of the simulated asphalt (gas and
liquids) increased from about 15% at the starting material to about 60% after 60 days of
heating.