模拟干酪根演化史的简易方法——演化指数法

EVOLUTION INDEX--A SIMPLE AND EASY METHOD FOR SIMULATING THE EVOLUTION HISTORY OF KEROGEN

杨文宽

Yang Wenkuan

地质矿产部石油地质综合大队

Research Party of Petroleum Geology, Ministry of Geology and Mineral Resources

利用一个建立在化学动力学理论基础之上的数学模型来模拟干酪根的自然热降解过程,这是有机地球化学和油气资源量预测技术的一项重要进展。利用数学模拟方法,人们根据少量基础资料(干酪根类型、温度史等)就能够定量地估计干酪根在各个地史时期的演化水平,从而有可能相当准确地回答其他研究方法(样品分析、人工热降解实验等)难于回答的某些重要问题。例如圈闭形成过程与油气生成过程是否配合良好,某些目前尚未钻探的地区或层位有无钻探价值,如此等等。

This paper proposes a mathematical model for the simulation of natural thermal degradation of kerogen. Kinetic parameters are determined on the basis of geochemical data of Chinese sedimentary basins. The apparent activation energy E is taken as 15600 cal/mol, and the apparent frequency factor A is taken as 6.7×106/m.y.. When the temperature history of source rocks is established the values of temperature index Ω would be achieved from Table 1. The evolution index S and the residual ratio a of potential carbon in kerogen could be obtained by the following equations: Si=(Ωi-Ωi-1÷Ωi,Inαi=-(S1+S2+……+Si).where n (℃/m.y.) is the ratio of temperatures, and i is the serial number of time intervals. The a value corresponding to the upper limit of principal zone of oil formation is 0.94 and a=0.55 may be used as indicator of the peak of oil generation. As a=0.06, the vitrinite reflectance would be about 2.0%. A lot of Chinese source beds have been simulated, and the results conform to the reality of natural geological sections.

https://doi.org/10.11781/sysydz198504268