Tight Sandy Gravel Reservoir Characteristics And Classification Evaluation Of Shahezi Formation Of Xujiaweizi Fault In Songliao Basin

With the development of tight glutenite gas exploration in Xujiaweizi fault depression,Shahezi Formation shows great exploration potential,Therefore,it becomes the primary work to study the characteristics and distribution of tight glutenite reservoir in Shahezi Formation.Based on the characteristics of the tight sandy gravel reservoir in the Shahezi Formation,the main controlling factors for effective reservoir formation are analyzed,and the reservoir types and favorable zones are divided,which can Provide basic geological data for the oil and gas exploration and development of the tight sandy gravel in the Shahezi Formation in the Xujiaweizi fault depression.Comprehensive use of core data,slice data,well logging data,etc.to study reservoir petrology characteristics,physical properties,storage space type,diagenesis,establish tight sandy gravel reservoir diagenetic evolution sequence,clarify the reservoir rock type and distribution characteristics,Reveal the physical property differences of reservoirs in different regions and different layers,and determine the lower limit of the physical properties of tight sandy gravel reservoirs in the Shahezi Formation;on the basis of previous research results and industry classification standards,establish evaluation criteria for the classification of tight sandy gravel reservoirs in the Shahezi Formation,And carry out reservoir classification evaluation;clarify the main controlling factors of effective reservoir development,and divide the favorable zone distribution range.The results show that the rock types of Shahezi Formation in Xujiaweizi fault depression are complex,mainly composed of glutenite.The type of sandstone is mainly feldspar detrital sandstone or debris feldspar sandstone,and the overall structure maturity is medium-low.The permeability of the rock samples of the Shahezi Formation in the Xujiaweizi fault depression is less than 0.01m D,accounting for about 73%,which is the typical tight sandy gravel reservoir.Porosity has a weak positive correlation with permeability,and permeability increases with increasing porosity.Reservoir storage space types are mainly primary pores,secondary pores,and micro-fissures,mainly dissolving secondary pores,with an average of about 80%.Empirical method and minimum flow pore throat radius method were used to determine the lower limit of reservoir physical property,with porosity of 2.9%and permeability of 0.04m D.According to the fact that bound water is mainly distributed in pore throats less than 100nm,the reservoirs of Shahezi Formation in Xujiaweizi fault depression are divided into Class I and II reservoirs.Sedimentary facies,diagenesis and tectonic position affect the distribution of favorable zones in the tight sandy gravel reservoirs of the Shahezi Formation.They are characterized by"facies-controlled reservoirs,dissolution and pore enhancement,and slopes are favorable".According to this,7Class I reservoir areas with an area of 142.3 km~2are divided,and 11 Class II reservoir areas with an area of 832.5 km~2,of which Anda area is the first favorable exploration area.