Burial and thermal history of Proterozoic source rocks in Oman
Abstract A geological and thermal history of the Proterozoic sedimentary basin in Oman was reconstructed to determine the time of hydrocarbon generation from the Proterozoic Huqf Group source rocks. Data from 97 exploration wells, and supplementary seismic reflection profiles were used to establish the burial graphs for the source rocks at all 97 locations. The overburden removed during formation of regional unconformities was estimated from regional geological data, compaction trends, and fission track analyses. The thermal history was reconstructed on the basis of present-day temperature data in the wells, heat flow models, and the palaeo surface temperature history. The calculated present-day surface heat flow map shows very low values (35–40 mW/m 2 ) over the basin axis, while on the edges the values are in the range 55–65 mW/m 2 . The results of the maturity calculations show that in northwest Oman oil generation occurred mainly during the Mesozoic, and that probably a large proportion of the traps in which reserves have been discovered was formed just before the last oil generation phase. However, in the central and southeastern part of the country hydrocarbon generation stopped about 400 Ma ago. This is due to the maximum burial temperature being reached at around that time. Considering the fact that almost all traps in which reserves have been located are significantly younger than the time of oil generation, one has to invoke processes of remigration to explain the oil occurrences. The geological data from Oman show that the eastern margin of the country, presently facing the Arabian Sea has been a high for most of its Phanerozoic history. The data on quantities of eroded and deposited sediments lend support for the theory that the margin was formed by a transform fault.