利用干酪根自由基浓度反演碳酸盐岩地层热历史

Inversion of thermal history in carbonate strata by using free radical concentration of kerogen

李慧莉 邱楠生 金之钧 何治亮 朱映康

Li Huili Qiu Nansheng Jin Zhijun He Zhiliang Zhu Yingkang

干酪根样品热模拟实验结果表明,随着干酪根热演化程度的增高,自由基浓度表现出先升后降的变化特征。自由基浓度的升高与干酪根较低演化阶段烷基侧链的断裂以及杂原子官能团的脱落有关;而自由基浓度的降低主要反映了高演化阶段干酪根所发生的缩合、聚合反应。自由基浓度受温度和加热时间的控制,由此可利用实验数据建立干酪根自由基浓度与温度-时间指数的定量关系式。通过反复调整剥蚀厚度、热流值,使自由基浓度的理论计算值与实测值吻合,反演碳酸盐岩地层的热历史。由于热模拟实验数据较少,目前所取得的研究成果只是一种新方法的探索,适用范围有限。今后,应进一步开展针对海相碳酸盐岩干酪根样品的热模拟实验及相应的研究工作。

Thermal simulation experiments of kerogen samples show that free radical concentration would first increase and then decrease along with increasing thermal evolution degree of kerogen samples.The increase of free radical concentration is related to the ruptare of alkyl radical side chain and dropout of heteroatomic functional group in lower evolutionary phase of kerogen;while the decrease of free radical concentration is the results of condensation and polymerization of kerogen during higher evolutionary phase.The free radical concentration is controlled by temperature and heating time,thus the experimental data can be used to establish quantitative relational expression between free radical concentration of kerogen and temperature-time index.The theoretically calculated values of free radical concentration should be fitted with the measured values by repeatedly adjusting denudation thickness and heat flow values,the inversion of thermal history of carbonate strata can thus be made.Since there are only a small amount of thermal simulation experimental data can be used in this study,the result achieved in this study is just for exploring a new methodology,and the scope of application is limited.Thermal simulation experiments and corresponding researches on kerogen samples from marine carbonates should further be carried out in the future.

10.11743/ogg20050312