Geochemical Characteristics Of Source Rocks And Oil Source Correlation Of Yingcheng Formation Of Lower Cretaceous From Lishu Fault Depression Of Song-Liao Basin

Lishu fault depression is located in the south of Song-Liao basin,The development of the source rocks is very well,there are large amounts of oil and gas resources.This article has carried on the systematic study of the source rocks and crude oil from Lishu fault depression of Song-Liao basin by the general chemistry experiment analysis method and the analysis of biomarker compound,combining previous research results to determine the geochemical characteristics of source rocks from Lishu fault depression,dividing the main hydrocarbon source rocks,conducting the Oil source correlation,giving a theoretical basis to Lishu fault depression's further exploration and development.1.Most of source rocks of Yingcheng formation from Lishu fault depression are medium-good,some of them is high quality.Among them,the high-quality source rocks are mainly distributed in the deep concave zone of southwest basin,Shuanglong concave and Houwujiahu to Xiaochengzi areas developed good hydrocarbon source rocks,Bawu and Beibuxiepo areas mostly developed medium-good source rocks,Qinjiatun and Pijia areas developed bad source rocks.The organic matter types of source rocks are mainly ? type and ? type.Most of the source rocks' organic matter maturity are in the mature stage,parts of them are in the high mature stage.Comprehensive above,the main source rocks of Yingcheng formation from Lishu fault depression distribute in the deep concave zone on the west side of the basin.2.From the central to peripheral of the fault basin,water salinity decrease,reducing continuously.The organic matter of source rocks from Yingcheng formation of Lishu fault depression has a dual sources,including low terrigenous higher plants and aquatic organisms,contribution of terrigenous higher plants is larger,they were the typical source rocks which developped in the rift lake basin.Most of the depositional environment of hydrocarbon source rock is a deep lake-half deep lacustrine facies,with deeper waters,relatively strong reducibility,and algae and higher plants are the main body of organic matter input;Part of the depositional environment is shallow lacustrine facies(SN65 well and SN118 well of Bawu area),with shallow water,weak reducibility,source rock organic matter input is given priority to with higher plants;For lakeside-fluvial facies sedimentary environment of source rock distribution in Shuanglong concave,the sedimentary environment of shallow water and weak reducibility,the source rock organic matter input is given priority to with higher plants.3.The crude oil from Yingcheng formation of Lishu fault depression has the characteristics of lacustrine oils,formed in the partial reducing sedimentary brackish water and salt water environment,the source of organic matter are mainly terrigenous higher plants,in addition to lower organisms including algae and bacteria.The distribution of normal alkanes' C10~C38 is complete,the vast majority of alkanes are unimodal type,most of the main carbons are C21.Amount of crude oil from oil fields,whose nC21-/nC22+,CPI and OEP values have changed little.The vast majority of tricyclic terpane series compounds of crude oil is main for C23 normal distribution,Crude oil samples after C26 long chain tricyclic terpane content is higher,shows the characteristics of "be cocky",The crude oil from Lishu fault depression have higher content of gammacerane,crude oil's gammacerane/C30 hopane ratio distributes in the range of 0.33~1.10.Most of crude oil is in the mature stage,and the crude oil from BK60 and SN54 area of Bawu oil field has the higher maturity.4.According to the geochemical characteristics of crude oil,the crude oil can be divided into the following three categories: ? type of crude oil's C24 tetracyclic diterpene/C26 tricyclic terpane has a value of 0.23~0.65,tricyclic terpane/rings triterpenoid has a value of 0.07~0.43,Ts?Tm,gammacerane/C30 hopane value is0.16~0.42;? type of crude oil's C24 tetracyclic diterpene/C26 tricyclic terpane value is 0.11~0.28,tricyclic terpane/rings triterpenoid value is 0.47~4.06,Ts>>Tm,gammacerane/C30 hopane value is 0.42~1.10;? type of crude oil's geochemical characteristics is between these two kinds of crude oil.5.The ? type of crude oil and the source rocks from Yingcheng formation of Lishu fault depression have similar steroid terpane composition characteristics,C28 tricyclic terpane and C29 tricyclic terpane have low abundance,the abundance about Ts with Tm is similar,C29 Ts and rearrangement of C30 hopane ‘s abundance is low,This shows ? kind of crude oil is from the source rocks of Yingcheng formation;While? kind of crude oil is clearly different from the source rocks of Yingcheng formation,these source rocks are not ? crude oil's sources,? kind of crude oil came from the source rocks of Shahezi formation;? type of crude oil is a mixture of ? and ?crude oil,which is supplied by the source rocks of Yingcheng formation and Shahezi formation.