Sedimentary Characteristics And Provenance Analysis Of Premian Shanxi Formation And Shihezi Formation In The West Linqing Depression

There are good prospects for oil and gas exploration in the western part of linqing depression.After years of exploration practice,oil and gas have been found in Permian strata of many wells in the region,and the sedimentary system of Permian transition facies-continental evolution has been established.However,because the Permian formation is not the main exploration strata of the oil field,the study of its sedimentary system lacks field profile evidence and comprehensive analysis of drilling data;Oil and gas exploration is mainly focused on source rocks,and the petrology,geochemical characteristics and material sources of the clastic rocks of the Permian shihezi formation are not studied.With the exploration of new shale gas resources,abundant data have been collected,so it is necessary to make a more detailed and systematic analysis on the sedimentary characteristics of shanxi and shihezi formation of upper Paleozoic and the material source of the clastic rocks of shihezi formation in western Linqing depression.In this study,the geological,drilling,geophysical and geochemical data in the western area of linqing depression were combined to identify the types of sedimentary facies of the shanxi formation and shihezi formation,and to analyze the longitudinal and planar distribution characteristics and sedimentary evolution rules of the sedimentary system.The petrological and geochemical analysis of the clastic rocks of the shihezi formation was carried out to explore their material sources.This paper tries to provide geological evidence of sedimentary petrology for the investigation of oil and gas resources of shanxi formation-shihezi formation in the west of linqing depression.Through the research,this paper comes to the following conclusions: According to the color,mineral composition,structural and structural characteristics of sedimentary rocks,paleontological characteristics,electrical characteristics and geochemical characteristics,combined with single well phase division and well connection comparison.The shallow-water delta sedimentary system developed in the shanxi formation is dominated by distributary channels and interdistributary bays in the delta plain.The shihezi formations mainly developed meandering river sedimentary systems,The main riverbed is spread nearly from north to south.In the late period of the upper shihezi formation,lake sedimentary system developed locally.The chemical alteration index CIA(67.59-94.70),plagioclase alteration index PIA(71.67-99.24)and chemical composition change index ICV(0.31-1.13)of the clastic rock samples of shihezi formation in the study area all indicated that the rock maturity was high and the source area underwent sedimentary recycling;The main element Al2O3/TiO2 ratio(mean value 29.56),trace element La/Sc(mean value 15.56),Th/Sc(mean value 3.34),Th/Co(mean value 1.35)and Eu value(mean value 0.69)indicate that the source rocks are felsic rocks;Qt-f-l,qm-f-lt standard triangulation diagram,sio2-k2 o /Na2 O discriminant diagram and the ratios of La/Y(mean 2.681),Th/Sr(mean 3.344)and Zr/Th(mean 17.99)all indicate that the tectonic environment in the source region is dominated by the passive continental margin.Based on the analysis of regional geological background and tectonic thermal events in the source region,the Inner Mongolia uplift located in the northern margin of north China is the main source region of the shizang formation clastic rocks in the study area.