The Genesis Of The Co Mbined Reservoirs In The Majiagou For Mation In The Central Of Ordos Basin

Ordos basin is one of the most important marine basins in western China.In recent years,CNPC has made a breakthrough in oil and gas exploration in ordos basin,indicating that it has a good prospect in ordovician pre-salt reservoirs.At present,the reservoir research under the submember of MW5 is inadequate.In order to clarify its reservoir characteristics,formation and development of pores,this paper carried out core observation,microscopic identification,logging interpretation and reservoir testing and reservoir geology research into MW6?MW7? MW9 in central basin,the study clarified the formation and distribution of reservoir,and predicted the favorable exploration zones.Through the research,the following results and conclusions have been achieved.Firstly,two sedimentary types of the target strata were defined,and the restricted platform facies developed in MW7 and MW9.The evaporative platform is mainly developed in MW6?MW7 and MW9.Secondly,the genesis of the dolomite reservoir in this area is clarified,and the study proposed that the reservoir is shoal facies dolomite and formed in penecontemporaneous dolomization.The types of the dolomite reservoir under salt-gypsalite are granular dolomite and crystalline dolomite.Dolomization occurs earlier than the burial compaction period,which is related to the seawater in the same period.On the basis of reservoir petrology,further clarify its reservoir space including dissolution pore(joint),intergranular pore(intergranular solution pore),intercrystalline pore(intercrystalline solution pore),is mainly controlled by the ancient terrain of sedimentary period and high frequency sequence interface,the former controlled the plane distribution of high quality reservoir,which determines the high quality reservoirs vertical horizon,on the basis of this,the paper predicted three favorable exploration zone.