The Characteristics And Origin Of Ordovician Karst Reservoir In Southern Ordos Basin

As one of the most important reservoirs of the world's oil and gas resources,carbonate reserves account for about 50% of the total reserves,is one of the important oil and gas exploration target.Ancient karst reservoir is one of the important types of carbonate reservoirs.The ordovician strata in southern ordos basin has experienced a long-time hiatus,the sedimentary formations from late ordovician to early carboniferous is missing,and the late ordovician carbonate experienced long-term weathering and denudation and freshwater leaching,formed a special karst ancient landform and karst reservoir,For large karst reservoir development to create a good geological conditions.Based on the observation of field geological section,core,the electron microscope,Scanning electron microscopy,physical property measurement,according to the characteristics infer the controlling factors of karst reservoirs.Then using the sample of southern ordos basin to carry out a dissolution simulation experiment,verify the hypothesis before us,The characteristics and causes of ordovician karst reservoir in the region were analyzed,studies have shown that:(1)Lithology is dominated by micrite,bioclastic limestone and calcarenite;(2)The main reservoir space types are divided into two categories,the reservoir space types are mainly composed of solution pores and dissolution fractures in limestone,and the reservoir space types are mainly composed of intercrystalline in dolomite,pore and enlarged solution pores;(3)The main diagenesis types: dissolution,cementation,and dolomitization etc.(4)The main control factors of karst reservoir formation include rock types,tectonic movement,dissolution and dolomitization.