000			02002nab a2200193 4500
005			20260520001805.0
008			260224s2009 xxu
245	0	0	_aGeochemical characterization of a biodegraded crude oil, Assran field, Central Gulf of Suez
260			_a _b _coct. 2009
270			_a28/06/2010 ; 28/06/2010
300			_a13 p. ; 343-355
520			_aTranscripción del resumen del autor. A crude oil sample from the Assran field in the Central Gulf of Suez (Egypt) was analysed geochemically and characterized in terms of a variety of source and maturity dependent biomarkers. Biodegradation was indicated by increasing concentration ratios of Pr/n-C17 and Ph/n-C18. However, biodegradation was only slight as GC-MS analyses of the saturate and aromatic fractions showed that hopanes, steranes, aromatic steroids and polycyclic aromatic compounds including sulphur heterocycles remained intact. The sterane and hopane distributions showed a predominance of C27 steranes, a low diasterane index, an abundance of gammacerane, a high homohopane index and an oleanane index < 0.2. The results indicate that the Assran-10 crude oil was derived from a marine carbonate source deposited in a highly reducing saline environment with a high bacterial contribution, consistent with the Upper Cretaceous Brown Limestone or Lower Eocene Thebes Formation containing Type IIS kerogen. Maturity parameters based on changes in the stereochemistry at chirality centres in hopane and sterane nuclei, such as C30 ba/(ba+ab) and C31 22S/(22S+22R) hopanes and C29 bb/(bb+aa) and C29 20S/(20S+20R) steranes, together with triaromatic sterane cracking ratios, indicate that the oil sample was marginally mature. The results also suggest that biodegradation is probably due to sulphate-reducing anaerobic bacteria.
581			_a4
773	0		_tJournal of Petroleum Geology _g32
942			_cARTICULO
100	1		_aHegazi, A.H. _943246
100	1		_aEl-Gayar, M.Sh. _943247
999			_c171479 _d171479