Petroleum evolution within the Tarim Basin, northwestern China: Insights from organic geochemistry, fluid inclusions, and rhenium–osmium geochronology of the Halahatang oil field

The newly discovered Halahatang oilfield in the northern Tarim Basin has a potential resource of > 70 Bbbls of oil.Oil organic geochemical data from the Halahatang oilfield indicate that the oils are of moderate maturity, biodegraded, and represent one oil family, derived from the same Paleozoic marine source.Modeling of coeval aqueous and hydrocarbon-bearing inclusion data provide fluid trapping temperatures and pressures of 100 to 110 ºC and ~39 to 59 MPa, respectively.The fluid inclusion data coupled with the previous basin model studies, suggests a single prolonged oil migration event during the Permian.Rhenium-Osmium (Re-Os) isotope data oil yield an Early Permian Re-Os age of 285 ± 48 Ma.The age agrees with the timing of maturation of the Paleozoic source via burial history modelling but is slightly older (~5 -55 myr) than the oil migration/accumulation timing implied by the basin modelling coupled with fluid inclusion analysis and the published reservoir illite K-Ar dates.Thus, the oil Re-Os date suggests that oil generation in the Halahatang Depression of the Tarim Basin occurred during the Early Permian, rather than the Silurian as previously proposed, with subsequent oil migration/accumulation occurring during the Mid-Late Permian as recorded by basin modelling, coupled with fluid inclusion analysis and illite K-Ar dating.In addition to promoting petroleum exploration in the Tarim Basin, this study that combines crude oil Re-Os isotope dating and traditional analytical methods (organic geochemistry/fluid inclusion analysis) to constrain petroleum evolution is applicable to hydrocarbon systems worldwide.