Distribution Characteristics and Enrichment Factors of Organic Matter in UpperPermian Dalong Formation of Shangsi Section, Guangyuan, Sichuan Basin
Zhang Yi
Zheng Shucan
Gao Bo
Feng Qinglai
Abstract：The black siliceous mudstones of the Upper Permian Dalong Formation in Sichuan basin are important target zones for shale gas exploration.To facilitate the unconventional hydrocarbon resources exploration in this area, scanning electron microscope (SEM) and elemental geochemistry were used to investigate organic matter types, distribution characteristics and enrichment factors in Dalong Formation.According to SEM pictures, organic matter in the Dalong Formation can be divided into morphological organic matter, amorphous organic matter and bitumen.Morphological organic matter is the result of selected preservation, discretely distributed in all lithology samples;disperse organic matter, which can be seen in siliceous mudstones but rarely in siliceous limestone samples, is the principle part of TOC (total organic carbon) of the Dalong Formation, reflecting the adsorption of clay minerals;bitumen formed from dissolved organic matter migration and subsequent high thermal evolution, is distributed in siliceous limestone and limestone samples, rarely in siliceous mudstone samples.Geochemical data indicate that anoxic environment is beneficial to the preservation of organic matter, but the productivity is the main factor to control the change of content of total organic carbon (TOC).Comprehensive correlation research shows that the sea-level rise of the Late Permian led to the increased productivity and anoxic water column in the adjacent oceanic basin.The high content of TOC in organic-matter-rich black siliceous mudstone is the result of sedimentary environment and mineral absorption, and also reflects preservation state of primary organic matter.Migration bitumen should be excluded for hydrocarbon source rock evaluation.
Keywords：Dalong Formationshale gasorganic matterdistribution characteristicsenrichment factorpetroleum geology
Publication Date：2017-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：18( 1008-1025 )