Research On The Reservoir Characteristics And Main Controlling Factors Of The Second Member Of The Sinian Dengying Formation In The Northern Sichuan Area

Based on the predecessors' research results,guided by reservoir geology,sedimentary petrology,petroleum geology and other theories,and based on field profiles,drilling and logging data and related analytical and laboratory data,this paper studies the stratigraphic and sedimentary facies characteristics,reservoir characteristics and diagenesis characteristics of Dengying Formation of Sinian in North Sichuan,and discusses the main controlling factors of reservoir development.Finally,this paper discusses the main controlling factors of reservoir development in North Sichuan.The favorable reservoirs in the 2nd Member of Dengying Formation are predicted.Sedimentary facies analysis shows that the 2nd Member of Dengying Formation in the study area is mainly platform facies,which can be further divided into three sub-facies:platform margin,restricted platform and slope.There are seven micro-facies:cloud lagoon,muddy lagoon,Point Beach(sand debris beach,oolitic beach),point hill,platform margin beach hill(granular beach,algae cohesive beach,algae hill),inter-beach depression and upper slope.The rock types of this layer are complex and diverse.Reservoirs are mainly distributed in granular dolomite,algal dolomite,grain dolomite and karst breccia.Reservoir space type is secondary generation and primary pore is less.?The primary pore is mainly residual intergranular pore,residual intragranular pore and lattice pore.?The secondary pore is mainly intragranular solution pore,lattice solution pore,intergranular solution pore,intergranular solution pore,intergranular solution pore,lattice solution pore,grape lace hole.?The third is crack,vertical crack,horizontal crack and oblique intersection crack.The porosity ranges from 0.33%to 5.12%,with an average of 2.15%.The permeability distribution ranges from 0.1 to 0.1?6.03 mD,with an average of 0.318 mD.According to mercury injection curves and pore throat parameters,the reservoirs in the study area can be divided into three types of pore structure:mesopore throat,mesopore throat and pore throat.According to the type of reservoir space and its combination characteristics,the reservoir types in the study area can be divided into pore type,pore type,fracture-pore type and Karst-cave type.Generally speaking,the reservoirs of the 2nd Member of Dengying Formation in the study area are mainly type ?-? reservoirs.Diagenesis of the 2nd Member of Dengying Formation in the study area is complex and diverse.The main types of diagenesis are:?constructive diagenesis,dolomitization,dissolution and recrystallization;?destructive diagenesis,cementation,compaction-compaction.The main controlling factors of reservoir development are sedimentation,diagenesis and tectonic movement.Platform margin beaches and mounds provide material basis for the development of high-quality reservoirs in the area.Compaction-pressure solution and multi-stage cementation are the basic reasons for the disappearance of primary pores.A large number of intergranular and dissolution voids formed by recrystallization and dissolution are the main reservoir spaces of the reservoir in the 2nd Member of Dengying Formation.The supergene karstification caused by the first episode of Tongwan Movement is the key to the formation of reservoirs.The superim position of platform margin beach mounds and supergene horizontal subsurface flow zones makes the reservoirs mainly distributed in the middle and upper part of the 2nd Member of Dengying Formation.The favorable reservoir facies belts of the 2nd Member of Dengying Reservoir Zone are mainly distributed along the Hanzhong-Ningqiang-Guangyuan-Yuanba area in an arc shape.Among them,there are limited platform-margin hilly-beach deposits in Guangyuan-Ningqiang and Jiange-Yuanba areas.The hilly-beach deposits are large in scale(up to tens of kilometers in continuous distribution)with a cumulative thickness of about 40-60 m,which are favorable reservoir development areas.In Wangcang Gucheng-Shuimu,Yuanba-Wangcang and north of Tongjiang(MS1 well),there are limited platform interior points and hilly-beach complexes with thin single-layer thickness and cumulative thickness of 20-50m.It is presumed that this area is a favorable exploration area.