Origin of oil geochemical compositional heterogeneity in the Radhuma and Tayarat formations heavy oil carbonate reservoirs of Burgan Field, south Kuwait

This is a qualitative assessment study to understand origin controlling lateral/geographic and vertical/stratigrahic heterogeneity of Radhuma (Palaeocene) and Tayarat (Maastrichian) Formation heavy oil reservoirs in the Burgan Field in south Kuwait. Data from oil analyses, including physical properties, bulk chemical composition, sulphur content, molecular chemical composition, and carbon and sulphur isotopes, were used to characterise the different oils in the reservoirs. Geochemical fingerprinting and characterisation suggest that the key impact on compositional heterogeneity has been the mixing of some petroleum—by the addition of lighter oil to extra-heavy oil. Therefore, the proposed complex filling history model for the Radhuma and Tayarat reservoirs consists of six episodes: two oil entrapments and four thermochemical sulphate reduction (TSR) fluid pulses. Finally, it is postulated that lighter fresh charge oils in the Burgan Field were sourced upward from deeper reservoirs associated with the reactivation of deep-seated faults as a result of structural compression events during Upper Cretaceous and Neogene time.