Analysis of Organic Matter Enrichment and Influences in Fine-grained Sedimentary Strata in Saline Lacustrine Basins of Continental Fault Depressions:Case study of the upper sub-section of the upper 4th member of the Shahejie Formation in the Dongying Sag
[Objective]The development of the"sweet spot"in lacustrine fine-grained sedimentary shale reservoirs is closely related to the enrichment of organic matter(OM).However,few studies on the causes of OM enrichment and the establishment of enrichment models of shale in faulted saline lacustrine basins have been reported.A typical continental rifted saline lake basin was developed for the upper sub-segment of the upper 4th member of the Shahejie Formation(Es4scs)in the Dongying Sag.To further understand the OM enrichment in fine-grained sedimentary shale during this period,[Methods]This study used thin slice identification,scanning electron microscopy,X-ray diffrac-tion,sporopollenin identification,biomarker chromatography-mass spectrometry and other techniques.The control-ling factors of organic matter enrichment were explored in detail by using each index,and the organic matter enrich-ment model suitable for each stage of environmental evolution of the study area was established.[Results](1)OM occurs at the microscopic level as strips,infills and dispersions.The OM source was mainly lower aquatic organisms such as algae,with evidence of small amounts of terrestrial higher plant material in the middle and upper strata.(2)The sedimentary environment evolved in three stages:A shallow-water semi-arid low-oxygen environment,a deepwater semi-humid reducing environment,and a sub-deepwater semi-arid low-oxygen environment.(3)OM enrichment was mainly influenced by climate,salinity,redox condition,productivity and deposition rate.Water depth,terrestrial input,volcanism and hydrothermal activity were secondary influences.[Conclusions]A model of OM enrichment in fine-grained sedimentary strata of the continental rifted saline lake basin was established,which may be highly significant for the exploration and development of continental shale oil and gas in China.To summa-rize:high OM enrichment in the studied interval was dominated by very productive conditions,a reducing environment for preservation,suitable salinity and suitable deposition rate.
lacustrine mud shalecontrolling factorsenrichment modesub-section of the upper 4th member of the Shahejie Formation(Es4scs)Dongying Sag
国家科技期刊平台
NSTL
万方数据
