海相高演化烃源岩总有机碳恢复系数研究

在5000余块海相烃源岩样品筛选结果的基础上, 根据90余块不同类型未成熟-成熟烃源岩的加水热压模拟实验结果, 并与自然演化剖面相结合, 对烃源岩有机质的变化规律及其恢复系数进行研究.海相优质烃源岩在未成熟-低成熟阶段(R_o < 0.8%) TOC (totalorganiccarbon) 变化不明显, 在成熟阶段中晚期TOC_残余随成熟度增加逐渐降低, 到高成熟-过成熟阶段变化又不明显.高成熟-过成熟优质烃源岩TOC_原始一般Ⅰ型最高降低40%, 恢复系数1.68;Ⅱ₁型最高降低32%, 恢复系数1.48;Ⅱ₂型最高降低24%, 恢复系数1.32.低有机质烃源岩(一般指0.3% < TOC < 1%) 随TOC变低, 降低幅度和恢复系数均逐渐变小, 当0.3% < TOC < 0.5%时, TOC_原始恢复系数约1.2, 当TOC < 0.3%时, TOC_原始恢复系数接近1, 可以不进行恢复.固体沥青和高有机质页岩(TOC > 30%) TOC_原始高成熟-过成熟阶段也不需要进行恢复.海相烃源岩(0.3% < TOC < 30%) 自然剖面生烃潜量的减少和模拟生排烃量的增加与TOC_残余的减少相吻合. 

Study on the Restitution Coefficient of Original Total Organic Carbon for High Mature Marine Hydrocarbon Source Rocks

On the basis of the results of hydropyrolysis simulations for about 90 different types immature to mature source rocks selected from about 5 000 marine source rocks in China, and accompanied by the investigation on the natural thermal evolution profiles, it was suggested that, the content of total organic carbon (TOC) of excellent marine source rocks does not change obviously at immature stage R_o < 0.8%, or at high-post mature stage R_o > 1.3%, and the residual TOC content decreases gradually with the maturity increase during the immature to low mature stage. The maximum of the decrease of the residual TOC content for sapropel (Ⅰ), Ⅱ₁ and Ⅱ₂ type kerogen from excellent source rocks is usually 40%, 32% and 24%, and the TOC restitution coefficient is 1.68, 1.48, 1.32, respectively. Both the amplitude and the restitution coefficient of TOC decrease gradually with the decrease of TOC content for the source rocks with low organic matter abundance (0.3 % < TOC < 1.0%), and the TOC restitution coefficient is 1.20 when 0.3% < TOC < 0.5%, and close to 1.0 when TOC < 0.3%. The TOC content of solid bitumen and shale with high organic matter abundance (TOC > 30%) also required no restitution at high mature stage. The decrease of S₁+S₂ of marine source rocks (0.3% < TOC < 30%) and the increase of the hydrocarbon quantity generated and expulsed in laboratory simulation are consistent with the decrease of the residual TOC content observed in natural thermal evolution profiles.