000			01863nab a2200181 4500
005			20260520001832.0
008			260224s2010 xxu
245	0	0	_aMain factors controlling the compositional variability of seepage oils from Trujillo State, western Venezuela
260			_a _b _cjul. 2010
270			_a20/07/2010 ; 20/07/2010
300			_a14 p. ; 255-268
520			_aTranscripción del resumen del autor. The organic geochemistry of eighteen samples of seepage oils from Trujillo State, Western Venezuela, was investigated. These oils are probably derived from the predominantly marine Cretaceous La Luna Formation which is near peak maturity for oil generation. A range of biomarkers (n-alkanes, acyclic isoprenoids, phenanthrene and alkyl-phenanthrenes, as well as dibenzothiophene and alkyl-dibenzothiophenes) were analysed by gas chromatography - mass spectrometry (GC-MS). The seepage oils have been modified as a result of water washing and biodegradation. A first group of samples were slightly biodegraded with the partial loss of n- and iso-alkanes. Other samples fall into two groups: those that are moderately degraded, with partial depletion of acyclic isoprenoids; and those that are severely altered, as indicated by the partial or total absence of hopanes. One objective of this work was to evaluate the factors influencing the compositional differences of the three samples sets. In-situ measurements, together with the interpretation of the geochemical data, suggest that diverse factors were responsible for these variations. These included different degrees of alteration due to biodegradation and water washing, as well as differences in flow rate towards the surface.
581			_a3
773	0		_tJournal of Petroleum Geology _g33
942			_cARTICULO
100	1		_aGalarraga, F. _945760
999			_c175094 _d175094