利用咔唑类化合物研究油气的运移——以塔里木盆地环阿瓦提凹陷志留系古油藏为例

咔唑类化合物是原油中极性较大的化合物,是研究油气运移的有效指标.在油气运移过程中,咔唑类与围岩发生作用而被吸附;苯并咔唑比苯并咔唑运移速度快;C₃-咔唑的极性相对于C₂-咔唑的较小而运移较快.因此,随运移距离增大,原油中的咔唑类化合物的含量将不断减少,苯并咔唑/苯并咔唑比值增大,C₂-咔唑/C₃-咔唑比值变小.塔里木盆地的第二期油气成藏发生在海西晚期,阿瓦提凹陷在海西期不断沉降,为塔里木盆地主要的生油凹陷,寒武系—下奥陶统源岩此时处于大量排烃期,根据上述几项含氮化合物指标的研究可知,排出的油气从生烃中心向四周呈辐射状运移,在构造高部位聚集成藏,晚海西期运动时被抬升至地表形成现今广泛分布的干沥青. 

STUDY OF PETROLEUM MIGRATION OF THE SILURIAN ANCIENT POOLS AROUND AWATI SAG IN THE TARIM BASIN USING CARBAZOLE COMPOUNDS

Carbazoles are polar compounds in oils,and they are useful indicators for study of hydrocarbon migration.In oil migration,carbazoles have effects with and can be adsorbed to country rocks;Benzoa]carbazole migrates faster than benzoc]carbazole;C_3-carbazole has smaller polarity than C_2-carbazole and the former can migrates faster.Therefore,with increasing the migrating distance,amount of carbazole in oil decreases,Benzoa]carbazole/ benzoc]carbazole ratio increases,and C_2-carbazole/C_3-carbazole value reduces.The second period of hydrocarbon reservoir formation in the Tarim Basin took place in later Hercynian.In Hercynian,the Awati Sag kept subsiding,and it was the major hydrocarbon-generating sag in the Tarim Basin.At that time,the Cambrian-lower Ordovician source rocks in the Awati sag were in the phase of large-scale hydrocarbon expulsion,and based on the above-mentioned indices of nitrogen compounds,the expelled hydrocarbons migrated in all directions from the hydrocarbon generation center and were trapped in structural highs.These hydrocarbon pools rose to the surface in the end of Hercynian and the hydrocarbons formed widely distributed dry asphalts.