This reference is for an abstract only. A full paper was not submitted for this conference.
Organic-rich mudstones of the Tuwaiq Mountain and Hanifa Formations of the Jurassic Hanifa Supersequence are the major source rocks for much of the oil in the Arabian Gulf. An integrated geochemistry and basin-modeling study on these source rocks and their oils was conducted to explain the distribution of petroleum accumulations within the Hanifa hydrocarbon systems of Qatar.
Principal component analysis (PCA) of biomarker and stable carbon isotope data for oils and condensates delineates three major hydrocarbon systems in Qatar:
Jurassic Hanifa-sourced oils,
Cretaceous Shilaif-sourced oils and,
Silurian Qusaiba-sourced condensates (Figure 1).
The biggest contribution to the PCA comes from Factor 1 where 63% of the variance in the data is primarily due to source rock facies variations. Oil-to-oil correlations indicate that the Jurassic Hanifa-sourced oils are present in both Jurassic and Cretaceous reservoirs.
The Hanifa sourced-oils exhibit relative thermal maturity differences between fields and by reservoir age (Figure 2). In general, reservoired-oils(Arab C, Arab D, Araej, Izhara, and Uwainat reservoirs) from the Dukhan, Maydan Mahzam, and Bul Hanine fields have higher relative thermal maturities than reservoired-oils from Al Rayyan, Al Shaheen, and Idd El Shargi. For a particular field, the relative thermal maturity of the oil appears to be related to stratigraphy, with the least mature oil in the youngest reservoir, and oil maturity increasing with reservoir depth. This is best observed in the Idd El Shargi field where the oil is least mature in the Cretaceous Shuaiba and Jurassic Arab C reservoirs and becomes more mature in the older (deeper) Arab Dand Uwainat reservoirs (Figure 2).
The occurrence of relatively higher maturity oils in deeper reservoirs (ArabD, Uwainat, Izhara) suggests that the reservoirs were filled from top tobottom. Figure 4 shows that in the Eastern Salt Province fields, the Hanifa source rock maturity increased from early mature to peak mature since50Ma. During this time, the deeper Izhara and Uwainat reservoirs of the EasternSalt Province fields were charged with higher maturity oils.