Upper Jurassic source rocks in the Sab´atayn Basin, Yemen: Depositional environment, source potential and hydrocarbon generation

摘要: The Sab’atayn Basin is a major hydrocarbon province in Yemen. Important source rocks occur Upper Jurassic units (Lam Member of the Madbi Formation, Formation). Depositional environment, potential and maturity were investigated using 60 cuttings samples from Tagina South-1 Well. All analysed for bulk parameters (total organic carbon (TOC), carbonate, sulphur, RockEval). A subset was selected biomarker analysis, pyrolysis-gas chromatography isotope investigations. carbonate-rich, euhaline, dysoxic to anoxic environment prevailed during deposition Lam Member. Bituminous shales within overlying Formation formed hypersaline, strictly depositional setting. Changes phytoplankton communities coincide with outlined changes water body. Upward decreasing d13C values suggest cycling due changing redox conditions. Member, at least 500 m thick, good very rock an average TOC 2.2%. hydrogen index controlled by maturity, but reaches 300 mg HC/g low (type II-III kerogen). produces sulphur-poor, paraffinic-naphthenic-aromatic low-wax oil. contain up 11% type II (to III) kerogen (HI: 427 TOC). These are excellent sources oil (and gas), their limited relatively thickness. Both, bituminous mature. deepest drilled part close zone main generation. Numeric models show that Cenozoic heat flow about 50 mW/m². An increase rifting likely, cannot be quantified. Major generation occurred Eocene–Oligocene times (assuming Late Cretaceous mW/m²) or both, 68 mW/m²).