Relationship Between Organic Matter, Sulphur and Phosphate Contents in Upper Cretaceous Marine Carbonates (Karabogaz Formation, Se Turkey): Implications for Early Oil Generation

Abstract

In this paper, we discuss the relationship between the organic matter, sulphur and phosphate contents of Upper Cretaceous marine carbonates (Karabogaz Formation) in the Adiyaman Petroleum Province of SE Turkey. The results of organic geochemical analyses of core samples obtained from the Karabogaz Formation suggest that phosphate deposition occurred in settings where the water column was oxic to sub‐oxic. However, the preservation of organic matter was favoured in anoxic environments. Moreover, the presence of sulphur (especially sulphur incorporated into kerogen) in organic matter‐rich layers led to early oil generation. The results of stepwise py‐gc analyses are consistent with a model in which, with increasing maturity, S‐S and C‐S bonds are the first to be eliminated from the macromolecular kerogen structure. Study of the maturity evolution of S‐rich kerogen by laboratory pyrolysis implies that marginally mature and/or mature kerogen in the Karabogaz Formation, which may be classified as classic “Type II” kerogen, was most probably Type II/S at lower maturity stages. This enabled oil generation to occur at relatively shallow burial depths and relatively early stages of maturation. It is reasonable to conclude that Type II/S kerogen, overlooked in previous studies, was abundant in TOC‐rich intervals in the Karabogaz Formation. Early generation (and expulsion) from Type II/S kerogen may have sourced the sulphur‐rich oils in the Adiyaman area oilfields.

Depositional Environment and Source‐rock Characterisation of Organic‐matter Rich Upper Santonian – Upper Campanian Carbonates, Northern Lebanon

“…May, 1991); however little is known about source rock type and distribution. Upper Cretaceous chalks, marls and shales are prolific potential petroleum source rocks in the eastern Mediterranean region (Henson, 1951;Renouard, 1955;Ala and Moss, 1979;Beydoun, 1988;May, 1991;Sharland et al, 2001;Tannenbaum and Lewan, 2003;Abed et al, 2005;Nader, 2011), and are proven to be a source for oil in Adyaman province, SE Turkey (Inan et al, 2010) and in the Dead Sea basin (Tannenbaum and Aizenshtat, 1985). Previous studies have attributed these marine organicmatter (OM) rich deposits to a high productivity system associated with extensive coastal upwelling developed during the Late Cretaceous along the SE Tethys margin (Almogi-Labin et al, 1993Ashckenazi-Polivoda et al, 2010SchneiderMor et al, 2012).…”