Study On Weizhou 11-B Oilfield Reservoir Characteristics And Water Law Of Jiaowei Reservoir Group

Weizhou 11-1B oilfield Jiaowei Reservoir group is currently in early development,sufficient energy in oil formation,the plane is divided into two blocks middle and east with inconsistent oil-water interface.The vertical develops two sets of high resistance and low resistance layer reservoir,low resistivity layer with high shale content and strong heterogeneity,and in which internal stem layer,calcareous inter-layer develops.According to the current situation of oil production,combined with the main problems,comprehensive study of reservoir is an urgent need to carry out.Based on the rock core observation,the results of the chemical analysis and the experimental analysis of the reservoir rock samples,the characteristics of the reservoir are studied.Through the analysis of cast thin section,scanning electron microscope?SEM?,Cathode luminescence,grain size,capillary pressure and oil saturation core test results particularly,we can evaluate the petrology,pore structure and physical property of Jiaowei Reservoir group,so as to analyze the Jiaowei Reservoir group's sedimentary facies and heterogeneity.Jiaowei group reservoir,porosity and super high porosity and high permeability oil and gas reservoir,is mainly containing quartz sand-powder sandstone,which is small particle size,moderately sorted,weak compaction and weakly cemented;pore types of reservoir are mainly inter-granular pore,secondly inter-granular dissolved pore and moldic pore,a small amount of impurity medium pore,inter-granular dissolved pores and the organism cavity.Diagenesis types include compaction,cementation,metasomatism and dissolution.Cementation is mainly carbonate cementation and clay mineral cementation.The compaction and cementation are destructive diagenesis,poor correlation with the reservoir property;dissolution is constructive diagenesis,increases of the porosity of the reservoir,but also leads to an increase in throat complexity,reduces the permeability of the reservoir.Sedimentation,diagenesis and pore structure are the main factors affecting the properties of the reservoir,the porosity will decrease with the increase in the size of the pores,the particles of supporting relatively loose and easy to fall off,and coarse sand with good roundness,so they also have good porosity correspondingly.The higher the content of shale in the stratum,the weaker the hydrodynamic condition,the reservoir physical property is correspondingly the lower.The effect of compaction on the formation of the diagonal tails is relatively small,which mainly consists of quartz and feldspar dissolution,which is widely developed in the area.Dissolution itself is a kind of diagenesis,which has a significant effect on the porosity of the reservoir.The formation of the main reservoir of the second in the section of the Jiaowei group reservoir formation mainly consists of the following two types:The first formation type—due to the sandstone top and bottom mud-stone or shale content rich in clay mineral transformation provide calcium,these basic compaction waters flow into sandstone,forms the early carbonate cements,this type mainly distributes in the mud-stone inter-layer and the high content of clay mud silty sandstone nearby;the second formation type:—under certain deep-buried condition,organic matter de-carboxylation and rock skeleton particles corrosion precipitates Ca²⁺,Mg²⁺,Fe²⁺ions and mix with oil and gas fluids and sandstone formation waters,which correlates with the oil-water interface occurring chemical reaction and equilibrium.The water saturation analysis have proved that the previous use of low resistance composite layer oil reservoir model is feasible to explain the early rule of water cut in low resistivity oil well;low resistivity layer due to the formation of movable water leads to the low electrical resistance,for oil and water seepage,water seepage ability stronger than oil,influxes into the well bottom,resulting in the rise of water cut,with movable water gradually to be produced,water cut decreased gradually in the well,resulting in water are on the rise again with the bottom water invasion in the later stage.