The Research Of Mesozoic Reservoir Properties And Characteristics In The Qiangtang Basin

The Qiangtang basin is located in the north-central Qinghai-Tibet Plateau in China,belonging to the eastern part of the Tethys tectonic,which is abundance with oil recourses.The basin held between the northern boundary of the Hoh Xi-Jinshajiang suture zone and the southern boundary Banggonghu Lake-Nujiang River suture zone.The Qiangtang Basin in Qinghai-Tibet Plateau is a Mesozoic marine superimposed basin.Mesozoic marine sedimentary is developed extensively,especially is the Jurassic system.Sedimentation types are diversified in the basin.The basin has rich oil and gas reserves with great exploration potential.Based on previous research data,the clastic rock and carbonate rock reservoirs are widely distributed in the Qiangtang Mesozoic Basin.Carbonate rocks are mainly exist in the Lower-Middle Jurassic Buqu Formation?Upper Jurassic Suowa Formation.Clastic rocks are mainly exist in the Lower-Middle Jurassic Quemocuo Formation?Xiali Formation and Lower Cretaceous A Bushan formation,while Upper Jurassic Xueshan Formation and Upper Triassic Xiao Chaka formation are composed of clastic rock and carbonate rock.The thicknesses of reservoirs are thickening from the southern and northern Qiangtang Basin depressions to the central uplift belt.Tu Pocuo-Bai Tanhu Deep sag in the north of Qiangtang depression and Tumen sag in south Qiangtang depression are the two reservoir area.From the regional view,Clastic rocks are generally exist in eastern Qiangtang Basin,and in western Qiangtang Basin,carbonate rocks are comprehensive.Generally speaking,the reservoir physical properties are much better in Xiao Chaka Formation,Que Mocuo Formation,Buqu Formation and Xueshan Formation.The reservoir space is mainly secondary pore and fracture,secondary porosity is mainly intergranular dissolution pores and intergranular dissolved pore;five types of diageneses are recognized,including compaction,cementation,corrosion,recrystallization and metasomasis.Compaction and cementation are the main factors leading to the low porosity and low permeability.However,corrosion,tectonic stress and metasomasis improve the physical property.In all the physical property of the reservoir are not so good,performing low porosity and permeability and pore structure characteristics of the poor.Cementation and Filling in the late multi-stage of diagenesis had mad reservoir porosity and permeability worse.Porosity and permeability data indicate poor reservoir properties in the region,as extremely low porosity and low permeability.This thesis conducted a study on the Mesozoic reservoir in order to analyze the physical property characteristics of the Mesozoic reservoir.In this thesis,we use seven test methods,including Thin Sections,Casting Body Slice,SEM,EMP,CLM,The whole rock X diffraction and Regular physical test etc.,marine reservoirs in the Qiangtang Basin have been studied,from the reservoir petrology,pore structure,diagenesis,reservoir physical property and factors affecting reservoir properties.In conclusion,referring to the outcrop samples and the test methods mentioned above,the analysis of Mesozoic marine reservoirs in the Qiangtang Basin show that the rocks' physical property in this area are poor,dividing the reservoirs into the low porosity and low permeability.