Characteristics And Controlling Factors Of The Subsalt Dolomite Reservoir In The Middle Group Of Ordovician To The Central Part Of Ordos Basin

In recent years,the exploration achievements of the subsalt dolomite reservoir in the middle group of Ordovician in the central part of Ordos Basin has shown excellent exploration prospectings.However,there is still a scarce of study on the recognition of reservoir features,pore genesis,and major factors that controlled pore formation.Based on the combination of core sample,well logging and geochemical ananysis,this paper characterized the reservoir type and the controlling factors of Om57?Om59.The following is the results:(1)The sedimentary environment of the Ordovician middle group dolomite in the study area is restricted platform,in which the gypsum-bearing dolomite flat and dolomitic flat are favourable for high-quality reservoir development;(2)The most important reservoir has been proved to be the dolomite reservoir,whose main pore space is intercrystalline pore,dissolved intercrystalline pore;(3)The dolomite in this area has experienced a process from penecontemporaneous dolomitization to penetration reflux dolomitization and burial dolomitization.(4)Microfacies is the base of reservoir development,the relative sea level cycles controls reservoir distribution,and diagenesis is the key factor of reservoir development,all of these constitute main controlling factors for the development of the reservoir in this area.