塔里木盆地轮南低隆起早古生代油气藏形成的期次与时间研究

Timing and Phases of Hydrocarbon Migration and Accumulation of the Formation of Oil and Gas Pools in Lunnan Low Uplift of Tarim Basin

塔里木盆地轮南低隆起早古生代地层中发现有大量运移沥青及有机包裹体。本研究应用地质地球化学相结合的方法对该区沥青及有机包体进行了研究 ,探讨了其与油气运移与聚集的关系。结果表明这些沥青与有机包裹体可大致划分为三期 :这三期沥青反射率分别是 :1.2 0 %～ 1.35 % ;0 .80 %～ 0 .95 % ;<0 .0 5 % ;与之对应的三期有机包裹体特征是 :黄绿色荧光 ,共生盐水溶液包裹体均一温度为 80～ 90℃ ;绿色荧光 ,均一温度 6 0～ 70℃ ;兰绿色荧光 ,均一温度 10 5～ 15 0℃。沥青与有机包裹体是油气生成与运移的直接证据。轮南低隆起早古生代地层中这三期沥青与三期有机包裹体的大量发现 ,说明在该区曾出现过三次较大规模油气生成与运移。结合该区埋藏史 ,受热史推断出这三期油气运移与聚集发生在晚志留世—早泥盆世 ,白垩纪—早第三纪及晚第三纪。本研究成果为该区油气藏的成因研究提供了重要依据。

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.