Geochemical Correlation of Crude Oils in the Nw Niger Delta, Nigeria

Abstract

Sixty‐six oils from eleven offshore and onshore fields in the NW Niger Delta, Nigeria were analyzed geochemically for their biomarker and isotopic compositions. Multivariate statistical analysis was employed to distinguish generic oil families from the large, complex data set. Biomarker and isotopic source parameter distributions were used to group the oils into three generic families. Family A oils, located in the onshore swamp to transitional area, received charges from predominantly Late Cretaceous or younger marine source rocks laid down in a sub‐oxic to oxic depositional environment. Family B oils occur in the near‐offshore area and are derived from Tertiary source facies that received an input of mixed terrigenous and marine organic matter. Family C oils, which dominate the offshore area, were derived from Tertiary source rocks typical of those deposited in oxic, nearshore or deltaic settings receiving significant terrestrial organic matter. Biomarker maturity parameters showed that the onshore (swamp) oils were generated at the peak of the oil generating window, while the transitional to offshore oils were expelled at an earlier stage of oil generation.

Carbon and hydrogen isotopic compositions of n -alkanes as a tool in petroleum exploration

“…From alkane and biomarker distributions, three oil families were deduced on the basis of source (terrigenous, mixed marine-terrigenous and dominant marine). Biomarker distributions including C 30 tetracyclic polyprenoids (TPPs) were used to calculate the TPP proxy (Holba et al 2003), oleanane indices (Eneogwe & Ekundayo 2003;Matava et al 2003), and the tricyclic terpane index (TTTI) to discriminate between the marine (mostly western deepwater oils) and terrigenous source rocks, and also to suggest mixing of lacustrine and terrestrial-derived oils.…”

Geochemical characterization of crude oils from well ‘X’, Agbada formation, onshore Nigeria

“…2). The organic matter of the Akata Formation is geochemically very similar to the Agbada Formations (Ekweozor and Daukoru 1994;in detail by previous works: Evamy et al 1978;Ekweozor et al 1979Ekweozor et al , 1981Udo and Ekweozor 1990;Ekweozor and Daukoru 1994;Ukpabio et al 1994;Nwachukwu et al 1995;Thomas 1995;Mosto Onuoha and Ekine 1999;Tuttle et al 1999;Haack et al 2000;Eneogwe and Ekundayo 2003;Eneogwe 2004;Obaje et al 2004). …”

“…An outstanding biomarker in the crude oils is the occurrence of 18α(H) oleanane, which is referred to an input of angiosperms (Ekweozor et al 1979;Ekweozor and Udo 1988;Riva et al 1988;Ekweozor and Telnaes 1990;Nwachukwu et al 1995;Haack et al 2000;Eneogwe and Ekundayo 2003;Eneogwe 2004). The oleanane index after Ekweozor and Telnaes (1990) (oleanane/C 30 hopane) is about 1 for all oils.…”

“…The oleanane index after Ekweozor and Telnaes (1990) (oleanane/C 30 hopane) is about 1 for all oils. Eneogwe and Ekundayo (2003) classified crude oils from onshore Nigeria in three different families based on light hydrocarbon distributions and biomarker parameters, e.g. oleanane/hopane ratio.…”

Petrology, Rank And Geochemical Evaluation Of Maastrichtian Coals From Se Nigeria: Implication For Petroleum Generation.

“…1). Eneogwe and Ekundayo (2003) identified three oil families (A, B, C) in the NW Niger Delta. Oils in family "C" were generated from source rocks with abundant terrestrial organic matter (OM), while family "B" oils were derived from source rocks with mixed terrestrial and marine OM.…”