Study On The Characteristics Of Tight Sandstone Reservoir Of Middle-lower Jurassic In The Eastern Part Of Kuqa Depression

Based on the well cores,typical sedimentary strata section and well logging interpretation results in the study area,combined with casting thin section analysis,scanning electron microscope experiment,clay mineral X-diffraction experiment,vitrinite Ro experiment and temperature measurement experiment of inclusions,etc.,the characteristics of sedimentary facies,reservoir characteristics and reservoir control factors in the study area were researched,and reached the following recognizes:The sedimentary facies of the Middle-Lower Jurassic in the study area was mainly developed braided river delta sedimentary facies.At the same time,meandering river delta sedimentary facies,lake sedimentary facies,and a few fan-delta sedimentary facies were developed.The Middle-Lower Jurassic reservoir rocks in are mainly litharenites,followed by feldspathic litharenites.The middle-lower Jurassic reservoir has experienced complex diagenesis,includes compaction,cementation,dissolution,authigenic mineral filling,fracture,etc.Compacted diagenesis and cemented diagenesis have the largest damage to the reservoir in the study area,and the effect of dissolution diagenesis and cracking diagenesis makes the reservoir physical property obviously better.It can be determined that the Middle-Lower Jurassic reservoir was in the middle diagenetic stage B to the late diagenetic stage.The sandstone diagenesis(assemblage)of the middle and lower Jurassic reservoir in the study area is divided into dissolution-primary intergranular pore,dissolution fracture phase,carbonate tight cementation phase and compact compacted facies.The Middle-Lower Jurassic reservoir sandstone in the study area can be divided into 4 types of diagenetic facies(combination): dissolution-primary intergranular pore,dissolution fracture phase,carbonate tight cementation phase and compact compacted facies.The dissolution-primary intergranular pore facies is mainly developed in the shallow layer in study area which is the best kind of reservoir,and the dissolution fracture facies is the most widely distributed in the study area which is reservoir with general reservoir property.The deep reservoirs in the Middle-Lower Jurassic in the western part of the study area are mainly developed with ultra-low porosity and permeability reservoirs and fractured pore reservoirs,the types of reservoir space are mainly secondary dissolved pores and micro-cracks.And the shallow reservoirs in the middle and lower Jurassic in the eastern part of the study area mainly develop medium porosity and permeability reservoir and pore-crack reservoirs,the types of reservoir space is mainly primary intergranular pores.The Middle-Lower Jurassic reservoir physical property in the study area is mainly controlled by the sedimentary environment,the granularity of the original sediment,the sorting of clastic grain and characteristics clastic components,and also influenced by the type and strength of the diagenesis.The sedimentary environment determines the quality of rock's original physical properties,and the original material composition of the rock determines its own potential for subsequent diagenetic transformation.