Single Sand Body Characterization And Geological Modeling Of Yan 8 Oil Layer Group In T225 Well Area

T225 well area is located in the south of Tianhuan sag in Ordos Basin.The main oil producing layer is Yan 8 oil layer group.The study area has been developed and put into production for more than ten years.With the increase of recovery degree,the water cut increases rapidly,and it is now in the middle and high water cut stage.The previous sand body research at the sand group level has not met the development needs.It is necessary to analyze and study the single sand body level of the sand body in the study area and establish a three-dimensional geological model to lay the foundation for subsequent fine reservoir description research.In this study,according to the data of core,logging and mud logging,the regional marker layer and auxiliary marker layer were identified.Combined with the data of sedimentary cycle and lithology thickness,the strata of Yan 8 oil layer group in the study area were divided and compared.By observing and identifying the sedimentary facies marks such as color,lithology and sedimentary structure of the core of the coring well,combined with the data of sandstone grain size analysis and logging curve characteristics,the types of sedimentary microfacies in the study area are determined,and the distribution characteristics of sedimentary microfacies are analyzed by single well and connected well microfacies sections and microfacies plan.By identifying short-term cyclic sequences and interlayers,the single sand bodies in the study area are divided,the spatial superposition and contact relationship of single sand bodies are clarified,and the distribution characteristics of single sand bodies in horizontal and plane are analyzed.Based on the study of sedimentary microfacies and single sand body,a three-dimensional geological model is established.Combined with the production dynamic data,the connectivity of single sand body is verified and the injection-production adjustment measures are put forward.Mainly obtained the following understanding:（1）The structural morphology of the Yan 8 oil layer group in the study area is generally high in the west and low in the east,and three structural high points are developed.The structural morphology of the Yan 8₁ sand layer group and the Yan 8₂ sand layer group is similar and has strong inheritance.（2）Four sedimentary microfacies of distributary channel,natural levee,interdistributary depression and swamp are developed in Yan 8 oil layer group.During the sedimentary period of Yan 8 oil layer group,four distributary channels intersected and merged in the north-central part of the study area,and bifurcated into four to five distributary channels flowing out of the study area along the northeast direction.Compared with the Yan8₂ sedimentary period,the four distributary channels entering the study area were significantly narrowed,and the proportion of interdistributary bays and natural levees increased significantly.（3）Four single sand bodies of Yan 8₁¹,Yan 8₁²,Yan 8₂¹ and Yan 8₂² are identified in the study area.The sand layers of single sand bodies in each period are mainly separated and superimposed in the vertical direction,and are mainly cut-stack in the lateral direction.On the plane,the scale of single sand body in Yan 8₁² period is slightly larger than that in Yan 8₁¹period.In Yan 8₁¹ and Yan 8₁² period,10 and 15 single channels are identified respectively.（4）Through the hard constraint of logging data,the three-dimensional geological model of Yan8₁ sand group in the study area is established by using the modeling method of stochastic modeling.The model shows that the sedimentary microfacies have a certain control effect on the lithofacies.The sand bodies in the distributary channel microfacies are more developed,and the physical properties and oil-bearing properties of the single sand body reservoir in the distributary channel are better.Through the effective water injection,the connectivity of single sand body in the study area was verified,and the injection-production relationship between the two groups of key well groups was analyzed.The specific measures of reperforating wells twice and reperforating wells seven times were proposed.