Simulating the timing of petroleum generation and expulsion from deltaic source rocks: Implications for Late Cretaceous petroleum system in the offshore Jiza-Qamar Basin, Eastern Yemen

The Mukalla Formation is one of the important petroleum source rocks in the Jiza-Qamar Basin, Eastern Yemen. In this study, coal, coaly shale and shale samples from three wells (Al-Fatak-1, 16/G-1 and 16/E-1) in the offshore Jiza-Qamar Basin were studied. The organic matter richness, kerogen type, thermal maturity, and petroleum generation potential of the Mukalla organic-rich samples were investigated. The analysed Mukalla source rock samples are potentially rich in organic matter of 1.01-84.40% TOC, ranging from good to excellent source rocks. The Mukalla source rocks primarily contain Types II, II-III and III kerogen, anticipating generating mainly oil and gas. This is generally consistent with the pyrolysis-gas chromatography results and further indicates that the Mukalla source rocks can produce high wax oil and condensate/gas. The thermal maturity parameters reveal the Mukalla source rocks are in mature to late-mature and are capable of generating oil and wet gas at the present time. In addition, this study was integrated the geo-chemical, geo-thermal and geological data in term of basin modeling study to simulate the timing of hydrocarbon generation and expulsion from the Mukalla deltaic source rocks. The basin model results indicate that the oil generation commenced during the late Eocene to late Oligocene, with a conversion ratio of 10-50 TR%. Furthermore, based on TRs of more than 50%, the most of oil was expelled along the micro-fracturing of the Mukalla source rocks and then trapped in the Mukalla Formation itself during the latest Oligocene and continued to present-day.