Keywords: 
• Tarim Basin /
• Lunnan Low Uplift /
• fluid inclusions /
• bitumen /

Abstract: Lower Palaeozoic strata in the Lunnan Low Uplift,of Tarim Basin, China, have recently been found to contain abundant migrated solid bitumen and petroleum-bearing fluid inclusions. In order to determine their origin and timing of the formation, bitumen/inclusion-rich core samples recovered from several wells in the area (mainly carbonate reservoir rocks and carrier units) were examined using a combination of organic petrographic and microthermometric techniques. Based on bitumen reflectance (BR o) measurements, solid bitumens were divided into three main groups, viz. (I) 1.20%～1.35%, (II) 0.80%～0.95% and (III) 0.05% . Hydrocarbon fluid inclusions were also grouped into three different assemblages based on their fluorescence colour and homogeneous temperatures ( T h): (I) yellow-green, T h = 80～90℃; (II) green, T h = 60～70℃ and (III) blue-green fluorescence, T h = 100～150℃. Spatial distributions of fluid inclusion Groups I, II and III within the structure closely match ed those for bitumen Groups I, II and III, respectively, and indicated that there were three separate episodes of large-scale oil migration and accumulation in the uplift. Using the BR o and inclusion Th data in combination with available burial and geothermal history in formation for the area, it was concluded that three corresponding phases of petroleum generation and migration took place during (I) Silurian to early Devonian, (II) Cretaceous to early Tertiary and (III) late Tertiary, from Cambrian-Ordovician source rocks. These findings provide useful insights into the complex origins of oil and gas pools in this region of Tarim Basin.