盐湖相低演化烃源岩的生烃机理及生物标志物演化特征——沥青“A”热模拟

柴达木盆地盐湖相低演化烃源岩沥青“A”的热模拟研究表明:在热作用下其排烃高峰在热模拟温度较低区间220~270℃，且以非烃和沥青质相对丰度最高为特征。沥青“A”在由未熟—低熟—成熟的演化过程中，各系列生物标志物的成熟速率不同，表现为正构烷烃＞藿烷＞甾烷。非烃和沥青质中含杂原子的极性化合物在热模拟温度300℃后开始大量发生脱羟基、脱羧基、脱羰基及链断裂反应。沉积有机质在低演化阶段甾烷C29 ββ/(ββ+αα)值异常高表明该地区细菌微生物发育。柴达木盆地低演化烃源岩在较低温度区间大量排烃，是细菌微生物对沉积有机质改造后其活化能大大降低所致。

Hydrocarbon Generation Mechanism and Evolution Characteristics of Biomarkers on Low-Evolutionary Source Rocks of the Salt Lacustrine Facies

Investigation of the thermal simulation of low evolutionary source rocks bitumen “A” of the salt lacustrine facies in Qaidam Basin indicated that the range of temperature on the hydrocarbon generating fastigium in the thermal function are 200～270℃, and the source rocks are characterized by high relative abundance of the nonhydrocarbon and asphaltene. The mature velocity of the biomarkers are different from the immature to low mature to high mature oil, and it’s sequence is alkane>hopane>sterane. The polar compound in the nonhydrocarbon and asphaltene, which have some atom other than carbon, have some reactions after 300℃ in thermal simulation, for instance, dehydroxylation, decarboxylation, decarbonyl and the chain cleavage. The ratio of sterane C29ββ/(ββ+αα) is very high in low evolutionary stage, indicating that there are some bacterium germs in this area. In low temperature range of low evolutionary source rocks in Qaidam Basin have generated a significant volume of hydrocarbon, consequently the activation energy of source rocks would become down because the depositional organic matter have been rebuilt by the bacterium germs.