Geological Survey And Evaluation Of Upper Jurassic-lower Cretaceous Oil And Gas In The South Of Sanjiang Basin

This paper takes the Boli basin,Jixi basin and Hulin basin as the research object.It is guided by the basin tectonics,sedimentology,organic geochemistry theory.The research takes the field investigation of petroleum geology and fieldsurvey as the main means,and carries out the system analysis of the sample test,combining with the drilling,logging and geochemical data to study on the characteristics of the upper Jurassic-Lower Cretaceous petroleum geological of study area.The research contents include growth characteristics,stratigraphic basin tectonic evolution stage,sedimentary characteristics,source-reservoir-cap assemblages and the characteristics of source-reservoir-cap assemblages.The Lower Cretaceous of study area are widely distributed.It has a set of coal bearing strata,including conglomerate,sandstone and mudstone.Chengzihe and Muling formation are the main strata in this basin group.The Mesozoic strata in the three basins are divided into there sedimentary facies.They are mainly fan facies,delta facies,lacustrine facies development.Chengzihe and Muling formation mainly developed shallow lake facies,local of basin developed deep lake facies,basin edge developed delta facies,the water deepen further during the period of Muling formation,sedimentary area was further expanded than Chengzihe formation.The dark mudstone of the Chengzihe formation and Muling formation in the southern part of the Sanjiang basin is of great thickness,good continuity and wide distribution,and is the main source rock series of Lower Cretaceous in the study area.The dark mudstone organic geochemical index better and the abundance of organic matter is high.Organic matter type is mainly ?kerogen;The maturity of organic matter entered the hydrocarbon generation threshold generally and began to enter into the stage of large-scale gas generation.According to basin outcrops and drilling core sample analysis in the study area,the main reservoir of lower cretaceous is the sandstone and pyroclastic rock of Muling formation,which belongs to low porosity and low permeability sandstone reservoir.According to the characteristics of sedimentary facies,the sand bodies are mainly distributed in alluvial fan and delta facies.The ldelta front facies is the best reservoir in the study area.In the study area,the cap rock of the Chengzihe formation(Yunshan formation)and the Muling formation(zhushan formation)is mainly mudstone,and is the tuff secondly.Regional seal of Chengzihe formation was developed.Local seal of Muling formation was developed.Based on the characteristics of time and spatial distribution of the source-reservoir-cap in this area,the source-reservoir-cap assemblage can be divided into two types:self-generation and self-preservation,lower-generation and upper-reserved.Considering favorable hydrocarbon generation indexes,such as TOC,thermal evolution,effective source rocks thickness,by using multiple geology factors overlay technique,the study predicted and delineated the favorable area of source rocks hydrocarbon generation of Chengzihe formation and Muling formation in the southern part of the Sanjiang Basin,which mainly distributed in the Central Depression of the Boli Basin,the Jidong Depression and the Muling Depression in the Jixi Basin and the Qihulin River Depression in the Hulin Basin.