摘要
陆源有机质在三角洲—浅海沉积体系中扮演着重要的角色,越来越多的深水区油气勘探实践发现存在陆源有机质的贡献,在琼东南盆地崖城组烃源岩甚至以陆源有机质为主,这引起了诸多学者的关注,但由于深水区烃源岩埋深较大、钻井较少,限制了该地区烃源岩研究及勘探进展。为明确陆源有机质分布特征,以琼东南盆地崖南凹陷崖城组地质背景为基础,设计陆源有机质沉积的水槽实验,用“正演”的方法对陆源有机质沉积过程进行观察,并对沉积结果进行取样,对样品进行粒度分析及TOC分析,结合大量分析测试数据及已有的现代河口陆源有机质分布研究实例,对陆源有机质分布特征进行分析,并建立分布模式。结果表明,由物源向深水区方向,陆源有机碳含量呈先增大后减小的趋势,在三角洲前缘—浅海过渡区出现最大值,古地形坡度越缓,水动力环境越弱,三角洲发育范围受限,陆源有机质搬运最远距离向物源方向迁移。
Terrestrial organic matter plays an important role in the delta-shallow sea sedimentary system.More and more oil and gas exploration practices find the contribution of terrestrial organic matter in deep-water areas.In the Yacheng Formation of the Qiongdongnan Baisn,the source rocks are dominated by terrestrial organic matter,which has attracted the attention of many scholars.However,due to the deep buried depth of the source rock and the lake in the deep-water area,the research and exploration progress of the source rock in this area is greatly restricted.Based on the geological background of the Yacheng Formation in the Yanan Sag,Qiongdongnan Basin,this study designed a flume experiment of terrestrial organic matter,which is a“forward modeling”method,to observe the deposition process of terrestrial organic matter and sample the sedimentation results.Particle size and total organic carbon(TOC)analyses were carried out on the samples,establishing a terrestrial organic carbon content prediction model through a large amount of analytical test data and applying the model to an actual research area with less data.We combine the qualitative observation of the experimental process and quantitative calculation results to establish a ter⁃restrial organic matter distribution pattern.The results show that the terrigenous organic matter is mainly deposited in the low-lying parts with a weak hydrodynamic force.From the source area to the deep water area,due to the interac⁃tion between the river and the sea water,the transport capacity of the river is reduced,and the organic carbon con⁃tent increases obviously in the shallow water.In a certain range of the shallow water area,due to the gradual decline of river transport capacity,organic carbon content decreased.Using the change of sediment grain size to reflect the hydrodynamic conditions,the correlation between hydrodynamic conditions and transport organic carbon content was explored,and the changing trend of terrigenous organic carbon content was predicted.This is consistent with the dis⁃tribution characteristics of terrigenous organic matter in modern estuarine sediments.According to the prediction,for Experiment 1(slope 3°-5°),the longest distance of terrigenous organic matter transport is 6.66 m,and the maximum of terrigenous organic carbon content is 4.4 m;for Experiment 2(slope 1°-3°),the maximum distance of terrigenous organic matter transport is 6.00 m,and the maximum content of terrigenous organic carbon is 4.12 m;for the Yacheng Formation(slope<0.1°),the maximum transport distance of terrigenous organic matter is 47.7 km,and the maximum content of terrigenous organic carbon is at 30 km.With the decrease of the paleotopography slope,the maximum transport distance of terrigenous organic matter also decreases,and the high value area of organic carbon content migrates to the source direction.The dominant distribution area of terrigenous organic matter is near the delta front shallow sea area.Based on the observation of the experimental process and the prediction of the changing trend of terrigenous organic carbon content,a single source"single peak"terrigenous organic matter distribution model map was established.In the delta plain area,the organic carbon content was mainly controlled by the growth and en⁃richment of in-situ organisms,which was the main control area of in-situ organic carbon.In the delta front littoral shallow sea area,terrigenous organic matter is deposited in large quantities,and its contribution may exceed that of shallow sea organisms,which is the main control area of terrigenous organic carbon.In the coastal shallow sea deep sea area,marine organisms are the main suppliers of organic matter,which is the main control area of marine organic carbon.The main control area of terrigenous organic carbon is the most favorable area for the development of terrige⁃nous marine source rocks.With multi-source intersection,the distribution characteristics of terrigenous organic mat⁃ter are superimposed for a single source,and the terrigenous organic carbon content in the source intersection area will be higher than that of a single source supply,which can also be used as the dominant area for the development of terrigenous marine source rocks.Using the first mock exam,we can predict the distribution of organic carbon for the Yancheng Formation in the Yanan Sag.The source of the northwest part of the Yanan Sag can transport the organic matter 47.7 km,that is,the transported organic matter can be transported to the center of the depression.The content of terrigenous organic carbon gradually increased from well Y1 to the center of the depression,and reached the maxi⁃mum at well Y4.Since then,the content of terrigenous organic carbon gradually decreased to the center of the depres⁃sion.The content of terrigenous organic carbon rapidly decreased from well Y6 to 0 in the center of the depression.This method can also be used to predict the distribution of terrigenous organic matter in other deep-water basins.
作者
屈童
高岗
徐新德
黄志龙
甘军
梁刚
游君君
QU Tong;GAO Gang;XU XinDe;HUANG ZhiLong;GAN Jun;LIANG Gang;YOU JunJun(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;CNOOC China Limited,Zhanjiang Branch,Zhanjiang,Guangdong 524057,China)
出处
《沉积学报》
CAS
CSCD
北大核心
2023年第2期584-600,共17页
Acta Sedimentologica Sinica
基金
中海油“十三五”油气资源评价项目(YXKY-2018-KT-01)
“十三五”全国油气资源评价项目中海油矿权区油气资源评价(2017YQZYPJ0109)。
关键词
三角洲—浅海沉积体系
分布规律
分布模式
水槽实验
陆源有机质
delta-shallow sea sedimentary system
distribution law
distribution pattern
flume experiment
terrestrial organic matter
