Simulation Of Terrestrial Organic Matter Distribution In The Delta Sedimentary System Of The Yacheng Formation In The Yanan Depression,Qiongdongnan Basin

The delta-shallow sea sedimentary system accepts both terrestrial organic matter and marine organic matter at the same time.With the progress of exploration and research work in the deep-water area of the Qiongdongnan Basin,it is confirmed that the source rocks of the Yacheng Formation are generally rich in terrestrial organic matter,and even the contribution of terrestrial organic matter is dominant.This has caused many scholars to pay attention to the laws of terrestrial organic matter enrichment in the delta-shallow sedimentary system.However,due to the large burial depth of source rock and less drilling in deep-water areas,the study of the enrichment law of terrestrial organic matter is greatly limited.Based on the study of sedimentary facies and organic matter distribution law of Yacheng formation in the study area,combined with the existing data and previous research results,this study designed the flume experiment of terrigenous organic matter distribution for the first time.The deposition and preservation process of terrigenous organic matter was observed and analyzed with the method of "forward modeling",and the deposition results were finely characterized and sampled.The samples were tested by particle size analysis,TOC,pyrolysis and whole rock X-ray diffraction analysis,and the prediction model of terrigenous organic carbon content was established.The distribution pattern of terrigenous organic matter was established based on the results of qualitative observation and quantitative calculation.The research results show that the overbank parts of the delta front,the dune countercurrent surface,the low-lying parts,the delta front slope area,and the prodelta-shallow sea area are the areas where terrestrial organic matter is dominantly enriched.The content of terrestrial organic carbon increases first and then decreases from the source to the deep-water area.The area near the delta front shallow sea sedimentary area is the most enriched area of terrigenous organic matter.This study provides an important evidence and guidance for the study of marine source rocks with terrestrial input and the next exploration in the deep-water area of Qiongdongnan Basin.