The Reservoir Characteristics Of Yingcheng And Shahezi Formation In The Jinshan Gas Field, Lishu Fault Depression

Jinshan Gas Field is located in the southernmost of southeast slope belt of Lishu fault depression in Songliao basin,which developed paleoslope for the long term,is the oriented region of oil and gas migration,the main production beds is Shahezi formation.The target layer in the study area have the characteristics of large buried depth,tight and low permeability,great heterogeneity,which haven't strated systemic study of reservoir microscopic characteristics,leading to unclear cognition of reservoir types,pore evolution and main control factors of effective reservoir,which severely restricted the process of exploration and development in the region.The target layer of the paper is Yingcheng and Shahezi Formation.based on core description,log and well logging date,and combined with sedimentary background of Yingcheng and Shaheziformation to study it's sedimentary facies;To study petrological characters,pore types and structure,diagenesis,the methods such as thin section observation,X-ray diffraction analysis,scanning electron microscopy(SEM),constant-rate mercury injection experiment,were employed,further make it explicit on different types of reservoir pore throat structure feature,diagenetic evolution sequence and pore evolution;by comprehensive analysis of sedimentary and diagenesis,to determine the main controlling factors of the reservoir effectively.Through the above research,several conclusions can be drawn:(1)Their are thirteen rock facies and six lithofacies combination,which correspond to different sedimentary subfacies;from Shahezi to Yingcheng formation,water become shallow of lake basin,basin expanding,sedimentary environment is from lacustrine sediments to continental delta deposits;(2)Reservoir'smain rock types is the lithic sandstone and feldspathic lithic sandstone which rich in the intermediate-acid extrusive rocks and granite debris et al;Interstitial matter is given priority to with clay cementation;Pore types include intergranular pore and dissolution pore,a small amount of gravel stick grain of seamand micropore;Diagenesis includes compaction,laumonite cementation,siliceous cementation and carbonate cementation and clay mineral cementation,the sandstone mainly in A,B period of middle diagenetic stage.According to the characteristics of diagenesis,dividedthe effective reservoir into laumontite cemented sandstone,chlorite siliceous cementation sandstone and weak compaction-calcium cementationdissolutionsandstone.different types of reservoir with different sedimentary environments,pore throat structure,diagenesis and pore evolution characteristics;(3)Reservoir is controlled by deposition and diagenesis.Pore developed well in sand gravel-coarse sand facies which have hard particle,there is a clear positive correlation between sorting and physical properties in Yingcheng formation.The porosity and permeability are not only embedded in depth,but are also influenced by many factors,such as rock compsitoon,diagenesis et al;chlorite cementation has a dual role,on the one hand to offset the overburden pressure to protect the primary pores,on the other hand if the chlorite membrane is thicker,the segmentation pore will be blocked,which greatly reduced the reservoir performance;the dissolution improves the reservoir quality,and the pores produced by the dissolution process account for 59.1% of the total porosity.In summary,through the study of subtle reservoir microcosmic characteristics,we can clear the main factor of effective reservoir.It will make an important guiding sign ificance to the oil and gas exploration of Jinshan area in future.