Reservoir Characteristics And Pore Evolution Of Jurassic Clastic Rocks In Sikeshu Sag,Southern Junggar Basin

Foreland fold and thrust belts are becoming one of the most attractive areas for the study of petroleum geology and hydrocarbon exploration.It is an important factor restricting oil and gas exploration and development that the pore evolution characteristics of reservoir are unknown and the quality of reservoir is different greatly.Four tree based on quasi south sag of the Jurassic clastic rock reservoir as the research object,the application of rock thin section observation,scanning electron microscope(sem),X-ray diffraction analysis and so on the many kinds of rock ore analysis of characteristics of the target strata in the study area reservoir petrology,reservoir space and physical property characteristics and systemic research on the characteristics of diagenesis,the key to establish diagenetic facies classification scheme,the reconstruction of the reservoir pore evolution history,Establishing a reservoir evolution model,and the results show that:(1)Jurassic lithic sandstone and feldspar lithic sandstone are mainly developed in the southern Margin of Junggar Basin,with rich reservoir space types and strong heterogeneity.There are coarse pore throats and intergranular pores with good connectivity,which are the main reservoir space types.There are also fine pore throats,low permeability intergranular and intergranular dissolved pores.The whole reservoir belongs to ultra-low porosity-ultra-low permeability,ultra-low porosity-ultra-low permeability.(2)Diagenesis has a great impact on the Jurassic clastic rock reservoir in the study area.There are great differences in the characteristics of compaction,cementation and dissolution in different layers.On the whole,the deformation of clastic particles caused by compaction is the main cause of pore loss.Cementation is mainly calcareous(calcite and anhydrite)and siliceous.Early cements are conducive to improving the anti compaction ability of the reservoir,The formation of late cement will lead to the decline of reservoir quality.The secondary pore formed by dissolution is the main factor to improve the physical properties of deep reservoir.(3)Based on the type and intensity of diagenesis,the diagenetic facies of Jurassic reservoir in the work area can be divided into strong compaction facies(class Ⅰ),medium compaction calcareous and strong cementation facies(class Ⅱ),medium compaction anhydrite strong cementation facies(class Ⅲ),medium compaction and dissolution facies(class Ⅳ)and medium compaction and strong dissolution facies(class Ⅴ).The longitudinal distribution of Jurassic diagenetic facies was identified by GR,AC,DEN,CNL and RT.(4)The Jurassic reservoir diagenetic evolution in the study area can be divided into shallow buried in the early stage,stage of tectonic uplift,continuous long-term shallow buried stage and late rapid burial stage,buried deep stage,has experienced many times of ph change alternately,combined with the characteristics of diagenetic evolution and pore evolution model and the coupling of burial history analysis,finally got dense accumulation and dense accumulation after the first two kinds of model of reservoir evolution,Longitudinally,favorable reservoirs are mainly concentrated in the bottom of Toutunhe formation and Qigu Formation,and horizontally,they are mainly concentrated in Gaoquan anticline.