二次生烃迟滞性定量评价方法及其在渤海湾盆地中的应用

Quantitative Evaluation Method of Secondary Hydrocarbon Generation and Its App lication in Bohai Bay basin

中国叠合盆地古生界烃源岩具有多次埋藏、异常受热、多次生烃和多次成藏的特点。不同成熟度、不同母质类型样品热解和高压釜模拟实验反映烃源岩的二次生烃不遵循Tissot经典的连续生烃演化模式 ,具有显著的迟滞效应 ,这种迟滞程度与烃源岩二次生烃时的原始成熟度有关 ,当Ro 等于 0 .9%左右时迟滞性最小。究其原因受化学动力学机制控制 ,二次生烃反应活化能的分布体现了一次生烃受热降解形成的中间产物在一次演化中止前未能有效释放而部分聚集在干酪根内的特性以及化学结构在冷却后的高度固化 ,导致二次增温初期中间产物的快速释放和化学结构再次活化的惰性 ,从而使得二次生烃显现出脉冲式的非连续演化过程。基于二次生烃迟滞性量版 ,结合渤海湾盆地具体地质条件 ,从生烃史和生烃阶段组合的关键要素入手 ,采用关键要素递阶优选原则 ,依次通过对显著生烃深度、生烃率等要素的递阶分析 。

Palaeozoic source rocks developed in Bohai Bay basin have the characteristics of multiple-burial, abnormally heated, secondary hydrocarbon generation, and multip le-reservoir formation. Based on the artificial simulation on secondary hydroca rbon generation and pyrolysis simulation on samples of different maturity , it is indicated that the evolution passway of secondary hydrocarbon gen eration do not follow the Tissot's model of continuous hydrocarbon generation. T h e obvious characteristics of secondary hydrocarbon generation is the lag effect and the degree of lag is related to the original maturity. The degree of lag is the least while R o is about 0.9%. This is determined by chemical kinetic m echanism. The activation energy distribution of secondary hydrocarbon generation indicate s that the intermediate products formed in the first hydrocarbon generation are not totally decomposed, and rapidly decomposed at the beginning of secondary hy drocar bon generation, but the chemical structure of kerogen quite solidify when cooled and become activated again during the secondary hydrocarbon generation. So the evolvement of secondary hydrocarbon generation present discontinuous pulse progr e ssion. According to the lag plate of secondary hydrocarbon generation and the ge ological condition of Bohai Bay basin, through the study of the history and stag e of hydrocarbon generation, and analyzing the obvious depth and ratio of secon dary h ydrocarbon generation, prospective areas of secondary hydrocarbon generation can be pointed out.