海相优质烃源岩形成重质油与固体沥青潜力分析

通过中国海相烃源岩、浮游藻、底栖藻等大量热压生排烃模拟实验与南方海相碳酸盐岩层系储层固体沥青发育特征相结合,认为海相优质烃源岩具备形成大量重质油及固体沥青的潜力。主要依据为:海相烃源岩主要成烃生物——浮游藻热压生油模拟实验表明在成熟早期(R_o为0.45%~0.7%)就出现生油高峰,可以大量生成以非烃+沥青质为主的重质油,每吨TOC生成的原油最高可达1 000 kg以上,它也是形成储层固体沥青的主体;海相未成熟优质烃源岩(Ⅰ—Ⅱ₁型干酪根,TOC大于2%)在成熟早期也可以大量生成以非烃+沥青质为主的重质油,每吨TOC总生油量可达300 kg,约占最高生油量的50%以上,总生烃量的40%以上,它随干酪根类型变差、有机质丰度减小(TOC小于2%)、碳酸盐含量变低(小于5%)而逐渐减少;中国南方二叠系、下志留统龙马溪组海相优质烃源岩在成熟早期形成的重质油及在准同生至成岩作用早期呈悬浮态运移出来的沉积有机质,经后期埋深高温裂解与聚合可以大量形成储层固体沥青。 

THE POTENTIAL OF GENERATING HEAVY OIL AND SOLID BITUMEN OF EXCELLENT MARINE SOURCE ROCKS

It is concluded that excellent marine source rocks have the great potential of generating heavy oil and solid bitumen,by combining the results of a great deal thermal pressure hydrocarbon generation and expulsion simulating experiments of marine source rocks,pelagic algae and benthic algae with the reservoir solid bitumen and their characteristics in marine carbonate rock in Southern China.The main evidences are as follows:(1) Thermal pressure simulating experiments of oil generation of the pelagic algae as the main hydrocarbon generation organism in marine source rock show that the maximum yield of oil appears at the early mature stages(R_o=0.45%-0.7%),a great quantity of heavy oil with asphaltene and non-being dominant can be generated at this stage,and the peak value of yield per ton TOC can reach to 1 000 kg.The heavy oil is the main component of forming solid bitumen in reservoirs.(2) Immature excellent marine source rock(type Ⅰ-Ⅱ₁ kerogen and TOC2%) can also generate a mass of heavy oil dominated by asphaltene and non-hydrocarbons at early mature stage.The total oil yield per ton TOC can reach to 300 kg,which accounts for about 50% maximum oil yield and 40% of the total hydrocarbon yield.The total yield of heavy oil gradually decreases following the kerogen type becoming poor,the organic matter content decreasing(TOC2.0%) and the carbonte content(5%) reducing.(3) The heavy oils generated from the excellent marine source rock at the early mature stage and the suspending organic matters moving out at the penecontemporaneous to early diagenesis in the Permian and Silurian stratums in Southern China,can form lots of soild bitumens by later burial and high tempe-rature cracking and polymerization.