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采用地质观察、实验模拟和数值模拟三者相结合的方法,研究了烃源岩有机质丰度变化的控制因素.由有机碳(TDCC％)的损失率DTOC=(TOC0-TOC)/TOC0(岩石原始有机碳)来衡量地史过程中烃源岩有机碳含量的变化时,其变化的幅度和方向取决于源岩中有机部分和无机部分的损耗量及相对大小.根据物质平衡关系分析导出了烃源岩成熟作用过程有机碳损失率DTOC的计算公式.当岩石类型和成熟演化历史一定时,TOC变化只与生排烃效率有关.在地质体的实际生排烃效率下,DTOC值一般变化在-0.05-0.2之间,计算的有机碳恢复系数k值仅0.90-1.25;只有在生排烃效率极高的理想情形下,DTOC值的变化才是显著的,k值可高达2.5.因此,基于有机质原始丰度恢复的碳酸盐岩烃源岩评价方法,可能过分强调了“减碳”的进程,很多情形下会美化原本比较差的烃源岩.
The controlling factors of organic matter abundance change in source rocks are studied by means of the combination of geological observation, experimental simulation and numerical simulation.The results show that the ratio of loss of organic carbon (TDCC%) DTOC = (TOC0-TOC) / TOC0 Raw organic carbon) to measure the change of the organic carbon content of the source rock during the geo-history, the magnitude and direction of the change depend on the amount of depletion and the relative size of the organic and inorganic parts of the source rock.According to the analysis of the material balance, When the rock types and mature evolutionary history are certain, the TOC change is only related to the hydrocarbon generation and expulsion efficiency. Under the actual efficiency of hydrocarbon generation and expulsion, the DTOC value generally changes Between -0.05 and 0.2, the calculated value of k for organic carbon recovery is only 0.90-1.25. Only in the ideal case where the efficiency of hydrocarbon generation and expulsion is very high, the change of DTOC value is significant and the value of k can be as high as 2.5. , The evaluation method of carbonate source rocks based on the recovery of organic matter abundance may overemphasize the process of “carbon reduction” and in many cases will beautify the originally poor source rocks.