Geochemical Characteristics And Oil-gas Potential Of The Lower Cretaceous Black Mudrocks In Luanping Basin

The Luanping Basin is located on the northern edge of the Yanshan Fold Belt in the North China Basin,with a remaining area of 800 km².This article is based on the study of the oil and gas potential of the Lower Cretaceous source rocks in the Luanping Basin,using the actual geological overview of Well LT-1 and core sample data,combined with the field geological survey results and outcrop samples,to carry out TOC testing,Rock-Eval analysis,kerogen maceral identification,Ro determination,kerogen organic element analysis,saturated hydrocarbon gas chromatography,chromatography-mass spectrometry analysis,major,trace element determination and whole rock X-ray diffraction and other analytical techniques and methods.This paper studies the source rocks of the Dabeigou Formation,Dadianzi Formation,and Xiguayuan Formation of the Lower Cretaceous in the Luanping Basin,especially the source rocks of the Xiguayuan Formation.Qualitatively evaluate the source rocks of the Dabeigou Formation,Dadianzi Formation,and Xiguayuan Yuan Formation by analyzing the abundance,type,and maturity of organic matter;by analyzing the characteristics of biomarker compounds,study the hydrocarbon sources of key Xiguayuan Yuan Formation The parent material source,thermal evolution degree of the organic matter in the rock,and the depositional environment of the source rock;through the analysis of the mineralogical characteristics,main amount,trace amount,and rare earth element characteristics,the paleo productivity,pale salinity,oxidation of the Xiguayuan Formation source rocks are studied Reducing conditions,paleoclimate and sedimentation rate,etc.,comprehensive analysis of the main factors controlling the organic matter enrichment of the Xiguayuan source rocks in the Xiguayuan Formation.Acquire the following knowledge:1.The source rocks of Lower Cretaceous in Luanping Basin are mainly Dabeigou Formation,Dadianzi Formation and Xiguayuan Formation.Among them,the Dabeigou Formation has good organic matter abundance,the type of organic matter is mainly type?₂ and type?,and the quality of source rocks reaches medium standards;the organic matter abundance of the Dadianzi Formation is poor,and the type of organic matter is mainly type?kerogen.The source rock quality is the worst among the three sets of horizons.The thermal evolution stage of both source rocks has reached the mature stage.2.The Xiguayuan source rocks in the Xiguayuan Formation have high organic matter abundance,with an average TOC of 1.28%;the organic matter types are mainly type?₂,type?₁,partly type?,and the microstructure of kerogen is dominated by the crust group and the inert group The content is the lowest,where the Ro value is 0.64%¹.32%,the organic maturity reaches the maturity stage,and the source rock comprehensive evaluation is good source rock.The characteristics of biomarker compounds indicate that the source of organic parent material is mainly phytoplankton,algae and other aquatic organisms,and terrestrial higher plants are mixed input;the biomarker isomerization index reaches balance and the organic matter reaches maturity.3.During the deposition period of the Xiguayuan Yuan Formation,organic matter carried by terrestrial debris and volcanism lead to medium-high productivity;the anoxic reduction of source rock deposits and the salinity conditions of brackish water bring excellent organic matter preservation conditions;fast The sedimentation rate and the semi-arid paleoclimate played a role in promoting or inhibiting the accumulation of organic matter in the source rocks,which comprehensively restricted the degree of organic matter enrichment in the source rocks of the Xiguayuan Formation in the Luanping Basin.