Diagenesis Of The M₅⁵sub-member Of The Ordovician Majiagou Formation In The Eastern Part Of Sulige Area And Its Impact On The Reservoir

The study area of this paper is the eastern part of Sulige,and the target stratum of this paper is M₅⁵sub-member Formation of Ordovician.The lithology of this layer is marine carbonate rock.The study of dolomite reservoir plays an important role in the exploration and development of carbonate oil and gas,and diagenesis is the most critical problem in the study of reservoir.Based on the theory of sedimentology,petrology and carbonate reservoir geology,and referring to the related literature at home and abroad,combined with the observation of core,thin section under microscope,scanning electron microscope and the analysis of other test materials,this paper studies the stratum,sedimentary facies,diagenesis and reservoir of Majiagou formation,Eastern Sulige,Ordos Basin Based on the study of diagenesis and reservoir characteristics,the influence of diagenesis on reservoir development is summarized.The results are as follows:Through systematic stratigraphic correlation,combined with lithology,logging curve and other data,the Ordovician Majiagou Formation in the study area can be divided into six strata:M1sub-member M6sub-member,and M₅⁵sub-member is further divided into two small layers,M5₅¹sub-member and M5₅²sub-member.Through the comprehensive analysis of the two sublayers,it is concluded that M5₅²sub-member is the thickest of the two sublayers.As a whole,the thickness of stratum M5₅¹sub-membe is relatively large in the whole study area,and the thickness of stratum M5₅²sub-member is not obvious.The stratum change of the whole sub member M₅⁵sub-member is relatively stable,and the thickest stratum in the southwest of the study area is relatively thin in the northeast.The main carbonate rocks in the study area are classified into dolomite and limestone.The limestone is further divided into grainstone,micrite limestone,secondary limestone and transitional limestone;dolomite is further divided into micrite limestone,micrite dolomite,silty dolomite and transitional dolomite.The diagenesis in the study area is divided into constructive diagenesis,destructive diagenesis and other diagenesis,and described respectively.The constructive diagenesis mainly includes dissolution,dissolution,dolomitization and recrystallization,and the destruction mainly includes cementation and compaction.The diagenesis,which has little influence on the reservoir in the study area,is summed up to other diagenesis,such as fracturing and de clouding.The diagenetic sequence and the influence of diagenesis on reservoir are summarized.On the basis of the above research,the related data and experimental results are sorted out and analyzed,and the reservoir distribution in the study area is predicted in combination with the comparison of reservoir physical properties and effective thickness.It is considered that the Majiagou Formation of Ordovician in Eastern Sulige contains class I,class II and class III reservoirs,mainly class III reservoirs.In the eastern part of M₅⁵sub-member is mainly composed of class III reservoirs,and in the west,there are class II reservoirs with good overall continuity.Among them,the reservoir with small layer of M5₅¹sub-member is the most advantageous,III reservoirs mainly concentrated in the southeast.