四川盆地东北地区吴家坪组海相页岩垂向有机质富集机制OA

The organic matter enrichment mechanism of marine shales in the Wujiaping Formation in the Kaijiang-Liangping Trough of the Sichuan Basin remains unclear,which restricts the identification of fa-vorable shale gas intervals and the planning of exploration deployment.Based on core data from well DY1H in the study area,using X-ray diffraction,total organic carbon(TOC)content,trace element and isotope analyses,this study investigates the sedimentary environment and organic matter enrichment mechanism of the Wujiaping Formation in Northeastern Sichuan Basin.The results show that the ma-rine shales of the Wujiaping Formation exhibit a clear three-stage vertical differentiation.During the deposition of the first member of the Wujiaping Formation,which was in the early stage of volcanic ac-tivity with a lag in volcanic material input,it is characterized by inefficient enrichment under terrigenous detrital dominance and weakly oxic conditions,with an average TOC content of 1.20％.The second member of the Wujiaping Formation represents a transitional phase,where the combined effect of nutri-ent input from volcanic weathering and dysoxic conditions promoted organic matter preservation,with an average TOC content of 5.40％.The third member of the Wujiaping Formation corresponds to the peak of volcanic activity.Under the coupled background of a humid climate and a semi-restricted stag-nant basin,a ternary high-efficiency enrichment mechanism of"volcanic nutrient input-biological enrich-ment-stagnant preservation"was established,with an average TOC content of 8.83％and a marked de-crease in terrigenous input.This reveals the dynamic patterns of organic matter enrichment under the synergistic control of tectonic,sedimentary,and climatic factors.These results provide guidance for deep shale gas exploration and block selection in the Sichuan Basin.