Organic Matter Enrichment Model Of Neogene Salt Lake Source Rocks In Yiliping Area,Qaidam Basin

The Yiliping area is located in the midwest parts of the Qaidam Basin.The Neogene in this area is a typical salty lacustrine sedimentary formation in China.Previous exploration studies have confirmed that the salinity difference in the saline formation often controls the characteristics of the source rock.distributed.Based on the data of drilling,logging,and geochemistry in the Yiliping area of the Qaidam Basin,this paper analyzes the sedimentary tectonic evolution,paleo-water medium,source rock development characteristics of the Neogene in this area.And established an organic matter enrichment model for different layers of source rocks in the area.The Neogene in Yiliping area was affected by the Himalayan movement.The center of the lake gradually migrated from west to east,and it gradually formed two sedimentary centers in Yiliping area.The sedimentary facies mainly consisted of braided river deltas and lakes.The paleoclimate of the basin gradually became arid and cold.The salinity of the ancient lake also gradually increased with the new formation,and the oxygen content in the water medium gradually decreased.In addition,the paleo-productivity was affected by the paleoclimate and tectonic evolution.The average productivity was 500 g/m~2*a,and the highest in the Shangyoushashan Formation was 515.80 g/m~2*a.The characteristics of organic matter enrichment are different in the eastern and western parts of the Xiayoushashan Formation.The abundance of organic matter in the western part of the project area is high,with aquatic source input being dominant,and the organic matter abundance in the east is lower and dominated by land-sourced inputs.The Shangyoushashan Formation is the circle distribution,the abundance of organic matter gradually decreases outward from the center,the source input type also shows a gradual transition from aquatic sources to mixed source inputs mainly based on land resources,The Shizigou Formation also shows a difference distribution between the east and the west.Extreme saltiness in the western region results in poorer organic enrichment.While the smaller areas in the eastern part are mainly aquatic,and the other areas in the eastern part is low in abundance with the land-based source inputs which being dominated.Based on the basin evolutionary differences and the differences in characteristics of source rock distribution of Neogene in the Yiliping area,the organic matter enrichment model of the source rock in each period was established.This not only enhances the formation conditions of the salty lacustrine source rocks in the Yiliping area,but also has a certain guiding significance for the exploration of the low abundance exploration area of Neogene in the Yiliping area.