The petroleum geochemistry of Oman provides a picture of considerable variey, since crude oils and their source rocks are found both throughout the country and throughout the stratigraphic column from the Infra‐Cambrian to the Tertiary. This paper reviews the geological history history of the area and places the petroleum geochemistry within the geological context. The oils can be geochemically classified into five groups. Three groups can be related to god oil source rocks found in the pre‐Cambrian Huqf Group, the Silurian Safiq and the Cretaceous Natin Formation. Another group of oils probably originates from the Upper Jurassic Diyab Formations, while the fifth group of crudes (named ‘Q’) cannot be correlated to a known source rock, but is inferred to have originated from an unsampled Huqf level. The “Huqf oils” are those that have been correlated to known Infra‐Cambrian Huaf source rocks, and are characterized by a strong C29 sterane predonominance and very light carbon isotope values of around‐36.0%. In contrast, the ‘Q’ crudes, drived from the unknown source are characterized by a C27 strerane predominance and carbon istope ratios of around ‐30.5%. Both the Huaf and ‘Q’ crudes also contain a series of characteristic compounds referred to as the ‘X’ compounds (all isomers of methyle and dimethyl alkanes). Oils reasoned to originate from Silurian Safiq source rocks have a week C29 sterane precominance, a significant content of rearranged steranes and carbon isotope ratios of ‐30.5%. The oils thought to originate from the Jurassic Diyab Formation have a similar sterane distribution but heavier carbon isotope values of around ‐26.5%. Finally, the crude oils from the mid‐Cretaceous Naith Formation source rocks are characteirzed by steranes with an equivalent distribution of C27, C28 and C29 isomers, and carbon isotope values of around ‐26.9%. These variations in biomarker distributions and carbon isotope values are sufficiently distinct to ensure a high degree of certainty in the grouping of the crude oils.

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The Petroleum geochemistry of Abu Dhabi onshore has been studied. From cutting and core analyses the presence of five main source rock intervals could be established in the Middle Cretaceous Shilaif Formation, the Lower Cretaceous Shuaiba Formation and Bab Member, the Upper Jurassic Dukhan Formation, the Upper Triassic Minjur Formation and the Permian Khuft Formation. Analyses of 13 crude oils resulted into five oil families. The Simsima reservoired oil of the Shah field appeared to originate from the Shilaif Formation source rock, while the Shuaiba oil of the Shah field is sourced from a shaly Bab Member source rock. The Kharaib reservoired oils in the Asab, Bu Hasa, Rumaitha, Sahil and Jam Yaphour fields originate most probably Irom Bab Member source rocks, while the Qatar and Habshan reservoired oils of the Bu Hasa and Shah field are likely to be related to Dukhan source rocks. For the Habshan oils of the Shah field, investigated in this study no matching source rock could be identified yet. Finally a maturity modelling study for the main source rock bearing Stratigraphie intervals was carried out.

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The petroleum geochemistry of Oman provides a picture of considerable variety since crude oils and their source rocks are found both throughout the country and throughout the stratigraphic column from the Infra-Cambrian to the Tertiary. The oils can be geochemically classified into five groups. Three of them can be related to good oil source rocks found in the Precambrian Huqf Group, the Silurian Safiq and the Cretaceous Natih Formations. Another group of oils probably originates from the Upper Jurassic Diyab Formation whilst the fifth group of crudes (name ‘Q’) cannot be correlated to a known source rock but is inferred to have originated from an unpenetrated Huqf level. The ‘Huqf oils’ are those that have been correlated to known Infra-Cambrian Iuqf source rocks and are characterized by a strong C 29 sterane predominance and very light carbon isotope values (δ C 13 ) of around −36.0‰. In contrast, the ‘Q’ crudes, derived from the unknown source are characterized by a C 27 sterane predominance and carbon isotope ratios of around −30.5‰. Both the Huqf and ‘Q’ crudes also contain a series of characteristic compounds referred to as the ‘X’ compounds (all isomers of methyl and dimethyl alkanes). Oils thought to originate from Silurian Safiq source rocks have a weak C 29 sterane predominance, a significant content of rearranged steranes and carbon isotope ratios of approx. −30.5‰. The oils correlatable to the Jurassic Diyab Formation have a similar sterane distribution but heavier carbon isotope values of around −26.5‰. Finally, the crude oils from the mid-Cretaceous Natih Formation source rocks are characterized by steranes with an equivalent distribution of C 27 , C 28 and C 29 isomers and carbon istope values of around −26.9‰.