优质烃源岩成烃生物与生烃能力动态评价

在海相优质烃源岩常规有机地球化学分析的基础上,综合利用仿真地层热压模拟实验与超显微有机岩石学等新技术对优质烃源岩不同成烃生物生烃潜力进行分析。结果表明:我国下古生界高过成熟海相优质烃源岩目前能够识别的成烃生物主要由底栖生物(或底栖藻类)及菌类(真菌类和细菌)组成,干酪根类型主要为Ⅱ型,这些海相优质烃源岩的原始生烃能力相当于Ⅱ型干酪根,其中底栖藻类相当于Ⅱ1型,真菌细菌类一般相当于Ⅱ2型;其次为浮游生物,生烃潜力与Ⅰ型干酪根相当。优质烃源岩中浮游藻类和底栖藻类在不同成熟阶段的生油能力不同,在高成熟—过成熟阶段生气潜力及其与原油裂解生烃的相对贡献也有差异。因此,下古生界高成熟度烃源岩需要根据不同类型的成烃生物或干酪根类型在各成熟阶段的生油、生气能力进行动态地评价。不同成烃生物生烃潜力研究不仅对常规油气勘探而且对非常规油气勘探也具有重要的借鉴意义。

Hydrocarbon-forming organisms and dynamic evaluation of hydrocarbon generation capacity in excellent source rocks

Based on the conventional organic geochemical analyses of excellent marine source rocks, simulation experiment and ultra-microscopic organic petrology were applied to study the hydrocarbon generation capacity of different hydrocarbon-forming organisms in excellent source rocks. The bio-precursors of excellent marine source rocks, kerogen type of which belongs to Ⅱ, is mainly composed of benthos (or benthic algae), fungi and bacteria. The hydrocarbon generation potential of these source rocks is equivalent to type Ⅱ kerogen, among which benthic algae is equivalent to type Ⅱ₁ kerogen while fungi and bacteria are equivalent to type Ⅱ₂ kerogen. The planktonic algae ranks second in hydrocarbon contribution,equivalent to type Ⅰ kerogen. The hydrocarbon generation capacity of planktonic algae and benthic algae varies during different mature stages. And in the high-mature and over-mature stage, their hydrocarbon generation capacity and contribution to oil-cracked hydrocarbon are also different. As to the high-mature source rocks in the Lower Paleozoic, a dynamic evaluation is demanded in view of the oil and gas generating capacities of different hydrocarbon-forming organisms or kerogens during each mature stage. The dynamic evaluation of hydrocarbon generation capacity of different hydrocarbon-forming organisms is important for the explorations of both conventional and unconventional oil and gas resources.