Reservoir Evaluation And Favorable Area Prediction Of Chang3 Oil-reservoir Of Triassic Yanchang Formationg In Yanwu-Sancha Aera,Ordos Basin

Since 2013,Jurassic reservoirs such as Yan224 and Zhen191 have been discovered in the Yanwu-Sancha area in the west of Zhenyuan Oilfield.The oil flow is also obtained in the Chang3 oil-reservoir of Zhen180 and Zhen164 blocks.The Chang3 oil-reservoir of Zhen180 district realized the rolling construction,and the Chang3 oil-reservoir of the Yanwu-Sancha area became the key layer of the next step of resource replacement.The main purpose of the project is to study the sedimentary characteristics and distribution of the Chang3 oil-reservoir in the Yanwu-Santun area and to find favorable construction areas.The main research method is the application of sedimentology,petroleum geology and other theories.Firstly,based on the comprehensive study of drilling core observation and logging curve,combined with the sedimentary background and reservoir lithology characteristics,sedimentary structure,particle size analysis,etc.The sedimentary facies marks determine the sedimentary facies of the braided river delta in the Chang3 oil-reservoir,and further divide the sedimentary microfacies such as the distributary channel,the underwater distributary channel,and the diversion bay.The planar distribution characteristics of the small sand bodies and sedimentary microfacies of the Chang3 oil-reservoir are analyzed by drawing the cross section of the well,the plane distribution map of the sedimentary facies and the contour map of the sand body.The analysis shows that the distributary channel in the study area is the main reservoir,and it is characterized by sedimentation in the west steep and eastward.The tectonic conditions are relatively simple,and the faults are not developed.In the background of western inclining monocline,a series of wide and slow,low-amplitude nasal structures are formed due to the extrusion and the differential compaction.Secondly,through the analysis of core and rock fragments,the Chang3 oil-reservoir of the Yanwu-Santun area is a medium-fine grain feldspar lithic sandstone with strong planar matter heterogeneity,and the clastic composition is mainly quartz and feldspar.Low permeability reservoir.The diagenetic facies of this area are mainly composed of chlorite film cementation phase and feldspar dissolution cementation phase.The porosity and permeability of feldspar dissolution phase and feldspar dissolution plus chlorite film cementation phase are better.Next,from the perspective of reservoir control factors,the structural unit of the study area is connected with the Tianhuan sag.Through the analysis of the structure,traps and sedimentary characteristics of the Chang3 oil-reservoir in the Yanwu-Santun area,the fractures in the area are not developed.Obviously,on the background of the west slope and the single slope,it is squeezed by the north-south direction and differentially compacted to form a series of nose-like structures dominated by east-west.It is believed that the reservoir type in the study area is dominated by tectonic-lithologic reservoirs,followed by lithologic reservoirs.The high structure has a certain control effect on the reservoir.Finally,the comprehensive sedimentary facies,reservoir characteristics and reservoir control factors are used to screen and classify the three favorable areas of the Chang3 oil-reservoir in the study area,which provides valuable exploration and development prediction for the next stage of scale production.