Geochemical Characteristics Of The Source Rocks Of The Laiyang Group In The Ri-Qing-Wei Basin

In this thesis,the typical sections of the Ri-Qing-Wei Basin and the Lingshan Island Scientific Drilling Well 1(LK1)are the main research objects.The organic geochemistry and elemental geochemistry are the main means,combined with the LK1 core samples desorption gas test.The geochemical characteristics of the source rocks of the Laiyang Group in the Ri-Qing-Wei Basin are studied.A marine sedimentary stratum dominated by deep-water gravity flow and deep-water traction flow is developed in the Laiyang period of the Ri-Qing-Wei Basin.The lithology of the stratum is mainly gravity flow sedimentation and siliceous clastic rocks,thick turbidite,siliceous rocks,siliceous siltstones,siliceous rocks and siltstone interbeds.The core of LK1 is a set of marine sedimentary strata with thick sandstone,siltstone,mudstone and shale interbed.The overall grain size is fine,with fracture zone,volcanic rock and conglomerate layer.Gravel and sedimentary rock layers have a cumulative thickness of more than 1000m.There are extrusion structures,load structures,water plastic folds,mudstone tears,liquefied sandstone veins,etc.,and calcite veins,pyrite,plant fragments,etc.are also found in some cores.The organic matter abundance of the Ri-Qing-Wei Basin is generally high,and most outcrop samples and core samples have reached medium and good source rock standards.In terms of organic matter type,the core samples of LK1 are all saprolite(type I),which has good hydrocarbon generation potential;most of the outcrop samples are saprolite(type I)and humic-soil Type(II₁ type),only the samples of the Lingshan Island Laohuzui Profile and the Jimo Zhougezhuang Section are humic(Type III),indicating that the Laiyang Group source rock in the Ri-Qing-Wei Basin has a high hydrocarbon generation potential.In terms of organic matter maturity,most of the samples were in the high maturity-over-mature stage,and the core samples of the LK1 belonged to the high maturity stage.The ratio of the main element SiO₂/Al₂O₃ reflects the low maturity of the sample components,m=100*(MgO/Al₂O₃)value,CaO/(Fe+Ca O)value,SiO₂-(Al₂O₃+K₂O+Na₂O)discrimination,B,B/Geochemical characteristics such as Ga value,V/(V+Ni)value,Th/U value,Sr/Ba value,Sr/Cu value,eanom index,and REE distribution pattern reflect the sedimentary environment of the Laiyang period in the Ri-Qing-Wei Basin.In the phase-reduction environment,the water body exhibits medium-high salinity characteristics,which may be a dry-hot climate,and a large amount of pyrite exists in the turbidite of the Laiyang Group in Lingshan Island,which indicates that the sedimentary environment is a reducing environment.The desorption gas test of the core samples of LK1 shows that the residual gas is not detected in most core samples,only a small amount of residual gas is detected in one sample,and most of the core is placed in the open air in the core box.Longer times may cause residual gases in the core to evaporate.