Study On Dolomitic Rock Reservoir Characteristics Of Permian Fengcheng Formation In Hashan Area

Under the guidance of theroies of sequence stratigraphy,sedimentology and reservoir geology,adopting integrating macro controlled context analysis in combination with microscopic mechanism analysis,geology in combination with geophysics,by comprehensive use of field outcrops,logging and three-dimensional seismic data,this paper built up the Permian sequence stratigraphic framework of Hashan area,studied the sedimentary facies types and sedimentary system spatial distribution characteristics which controlled by sequence.Then further analsyed the formation mechanism of dolomite,made sure about controlling factors of dolomitic rock reservoir.And predicted beneficial reservoir zones by use of a combination of means such as geological parameter,physical geography.Finally comprehensive appraised and pointed out advantageous oil gas accumulation area belt combined with real-time production data.The research result shows that the Permian Fengcheng group of Hashan area is relatively stable,having an obvious thickness center in the Fengnan3,Fengnan 5 well area and their south.According to the rock electrical characteristics and seismic facies,Fengcheng group can be divided into three sections.The lithology of the first and second sections changes from dolomitic rock,salinastone to pyroclastic rock from west to east,the lithology of the third section is mainly clasolite.Combined with regional tectonic background,through analysis of paleosalinity,palaeoclimate redox conditions,the Permian Fengcheng group depositional setting of Hashan area is a evaporate half salined-salined closed lake.On this basis,according to the analysis of core facies,electrofacies,seismic facies and grain-size statistical analysis,this paper recognized the three main sedimentary facies types in Hashan area: fan delta,shallow lake,semi-deep lacustrine,then defined the sedimentary facies features of different layers and their evolvement rules.According to the dolomite diagenetic environments and output state analysis,dolomite in Fengcheng group of Hashan area has three genetic types: parasyngenetic origin,hydrothermal origin and burial origin.It is mainly parasyngenetic origin in the ancient slope area,hydrothermal origin and burial origin in shallow lake,semi-deep lacustrine belts.Looking from longitudinal,dolomite developed in the first and second sections of Fengcheng group.In the third section,the development of dolomite was restricted because terrigenous detrital Supply increased in sedimentary period,mainly developed dolomitic sandstone in fan delta front.The reservoir space of dolomite are various,including primary pores,secondary pores and fissure.Among them,fissure accounts for 50 percent.So the development of fissure controls the distribution of effective dolomitic rock reservoirs.Statistical results show that the development of fissure controlled by lithology and fault.Under the effect of fault activity,higher dolomitic degree and stronger brittleness is beneficial to the formation of fissure.Through comprehensive analysis of seismic attribute,facies and zones,ancient landform,fault,the paper divided dolomitic rock into three levels and predicted beneficial dolomitic rock reservoir zones.The?level reservoirs were mainly developed along the Hashenxie1-Fengnan8 well area and Fengnan5-Feng5-Haqian20 well area in where faults were developed.The?level reservoirs developed in ?and ? nappes were distributed in annuluses along the?level reservoirs.The ? level reservoirs were mainly developed in ? and ? nappes in which area dolomitic rock was low-development.