Characteristics Of Lacustrine Dolomite Reservoirs In The 5th Oil Group Of Sha 3 Of The Paleogene In Tanggu Area

This paper aims at lake dolomite of Paleogene Shasan 5 oil formation in Tanggu area.Under the guidance of carbonate sedimentology and reservoir geology,on the basis of stratigraphic and sedimentary analysis,mineral and rock types are analyzed by means of core,thin section and electron probe.The type of reservoir space was divided by casting thin section,core and scanning electron microscope.The methods of high pressure mercury injection,constant speed mercury injection and cryogenic nitrogen adsorption were used to classify the types of storage space and analyze the characteristics.The single well reservoir is divided and the distribution area of reservoir is forecasted.Mineral types include dolomite,calcite,pyrite,quartz,feldspar,clay minerals,barite and so on.The rock types are mainly argillaceous-powder dolomite,argillaceous dolomite and granular dolomite.The mineral contents of different types of rocks vary greatly.Dolomite output state includes stratiform,uniform,nodular and so on.According to the size,the reservoir space can be divided into three types:macroscopic dissolution pores(caves),microscopic pores and fractures.According to the origin of pores,they can be divided into primary intergranular pores,primary intergranular pores,corrosion pores,intercrystalline pores,intragrystalline pores,mold holes,etc.The fractures can be divided into high Angle fractures,horizontal fractures,reticular fractures,dissolving and expanding fractures,closed fractures,sutures,and nanoscale fractures.The inclination,elongation,opening and filling conditions of each type are analyzed.The microfracture widths were mainly distributed between 10?50?m and 100?500?m.The measured core porosity is mainly distributed between 2.38 and 16.83%,with an average value of 9.09%(<15%).The gas permeability is distributed between 0.0016 and 3.576mD,with an average value of 1.92mD(<10mD),belonging to low-porosity and ultra-low-permeability reservoirs.Pore structure characteristics were analyzed by means of high pressure mercury injection,constant speed mercury injection and cryogenic nitrogen adsorption.There are four types of reservoirs,including pore,pore,fracture and micropore.The lithology,mercury injection characteristics,productivity,displacement pressure and reservoir availability of each type are summarized and compared.Combined with the type of orifice belt and main controlling factors,the characteristics of single well,transverse and plane of orifice belt are analyzed.The pore-fracture zone is mainly distributed in the high part of the fault block and the area on both sides of the fault,such as tang29-26c and tang39-2,which are obviously affected by tectonic action and dissolution.According to the reservoir evaluation criteria,the reservoir types in the study area are divided into three types.The reservoir thickness of all single wells was evaluated.From the plane analysis,? class reservoir distribution area is relatively small.? reservoir mainly along the ? class peripheral reservoir distribution.