摘要： 与古气候和古环境息息相关的有机质发育特征的高精度预测,是油气地质研究的核心和难点,对中—低勘探程度沉积盆地常规油气或中高勘探程度沉积盆地中非常规油气的高效评价部署具有重要意义。本研究利用旋回地层学、地球化学技术,通过东营凹陷FY1井古近系沙河街组三段下亚段的高频旋回地层划分和古环境、古气候、有机质地球化学、矿物学分析,探索陆相泥页岩有机质在不同尺度旋回地层中的富集规律。结果表明: (1)在东营凹陷古近系沙三下亚段中识别出2个1.2 Ma超长斜率旋回、5个400 ka长偏心率旋回、21个96 ka短偏心率旋回、42个51 ka斜率旋回、103个19 ka岁差旋回。结合前期研究成果,以1.2 Ma、400 ka、96 ka波形曲线为依据,识别出2个长期、6个中期、21个短期基准面旋回; (2)东营凹陷沙三下亚段沉积时期古环境恢复与TOC数据对比分析证明,古气候演化与有机质富集之间基本同步,均受控于天文旋回,即超长斜率增大或长偏心率增大时期,气候温暖湿润,基准面升高,地层还原性增强,有利于有机质富集; (3)有机质的富集主要取决于古气候温暖湿润程度控制的古生产力和湖盆水体深度控制的有机质保存环境,长期与中期尺度旋回对有机质富集的控制程度高于短期旋回,因此在长期、中期尺度上,可以旋回波形曲线为依据进行古环境恢复和富有机质层的厘定。

关键词: 有机质富集, 旋回地层学, 古气候, 东营凹陷, 古近系, 沙三下亚段

Abstract: The precise prediction of organic matter,which is closely related to palaeoclimate and palaeoenvironment,is the core and difficulty of petroleum geology research. In this study,cyclic stratigraphy and geochemical techniques were used to identify the high-frequency cyclic strata and analyze the palaeoenvironment,palaeoclimate,organic matter geochemistry and mineralogy of the lower sub-member of Member 3 of Shahejie Formation($Es_{3}^{L}$)in Well FY1,Dongying sag. The results show that: (1)Two 1.2 Ma long-term obliquity cycles,five 400 ka long eccentricity cycles,21 short eccentricity cycles of 96 ka,42 obliquity cycles of 51 ka and 103 precession cycles of 19 ka are identified in the $Es_{3}^{L}$ of the Paleogene in Dongying sag. Combined with the previous research results,based on the waveform curves of 1.2 Ma,400 ka and 96 ka,two long-term,six medium-term and 21 short-term base-level cycles were identified. (2)The correlation between the depositional environment of $Es_{3}^{L}$ and TOC data indicates a synchronization between palaeoclimate evolution and organic matter enrichment,which are controlled by the astronomical cycle. During the long obliquity or long eccentricity increased period,the climate become warmer and result in a raised base-level,enhanced reduced environment and favorable environment for organic matter accumulation. (3)The degree of organic matter enrichment depends mainly on the palaeo-productivity controlled by the wet climate and preservation condition controlled by paleo-lake depth. The long-term and medium-term scale cycle has a dominated control on organic matter enrichment. Therefore,the waveform curve of the long-term and medium-term scale cycle can be used to reconstruct the palaeoenvironment and locate the rich organic matter layer.

Key words: organic enrichment, cyclic stratigraphy, palaeoclimate, Dongying sag, Paleogene, lower sub-member of Member 3 of Shahejie Formation

中图分类号: 

• TE122.2