The Research On Characters Of Sedimentary Facies And Reservoir Sand-body Of Chang6Formation In North Of Jiyuan Area

The sedimentary facies including division symbol,microfacies combination anddistribution character in space is analysed from point to line and final in the surfacewhich is based on Outcrop and cores observation, electrofacies and the achievementfrom previous study,After that, the microscope character of reservoir sand-body suchas petrology,physical property,the type and the configuration of pore,combining themacroscope character of sand-body including original type,distribution of space andheterogeneity is developed.The conclusion is in the following paragraph.The sedimentary facies of Chang6formation in north of Jiyuan area is deltafront subfacies, including the microfacies of subaqueous distributary channel,subaqueous natural levee,mouth bar and crevasse channel. The distribution ofsubaqueous distributary channel is from northwest to southeast as the shape ofbelt,and is divided by argillaceous sediment.In the period of Chang63,the subaqueous distributary channel developed well inthe whole,which has a great degree on lateral migration,and the mouth bar is alsodeveloped well.In the period of Chang62, the development of subaqueousdistributary channel is relative poor, and the scale of channel is small which migratesfrequently in lateral,so the condition of hydrodynamic power is weak and unstable.In the period of Chang63,the hydrodynamic power is strong,and the sedimentary ofsubaqueous distributary channel is stable which has a large scale,but thedevelopment of mouth bar is weak relatively.The main type of sandstone is lithic arkose and arkose. The major component ofinterstitial is kaolinite and ferroan calcite.The size grade is fine-sand and silty-sandin chief.Testing result of porosity and permeability shows that the porosity is from 3%—15%in main,but the extension of permeability is a bit wide,which is between0.01×10-3μm2and0.3×10-3μm2,and the highest reaches to2.37×10-3μm2. Theporosity of Chang61,62,63oil formation is increasing successively,and the value is8.54%，9.08%，9.22%respectively.In the same,the permeability shows the similarvariability,which is0.15×10-3μm2，0.26×10-3μm2,0.30×10-3μm2respectively fromChang63oil formation to Chang61oil formation,and the correlation between porosityand permeability is well. The main type of porosity is original intergranular pore andthe dissolved pore of feldspar. The curve of mercury penetration is II type inmajor.The combination of pore throat is small pore combining micro-throat andmicro-pore combining micro-throat.The statistics of sand-body thickness in Chang6oil formation shows that the averagethickness from Chang63oil formation to Chang61oil formation is decreasedgradually,and the value is14.19m,12.95m,12.45m respectively. The averagethickness of subaqueous distributary channel is between5.5m and6.5m. The averagethickness of mouth bar is between5m and6m. The average thickness of channelflank is between4m and5.5m. The average thickness of subaqueous natural leveeand crevasse channel is between3m and2m,2m and1m respectively.Thewell-to-well profile of sand-body shows that the sand-body in the area ofGufengzhuang and Mafang has a preferable connection,and the connection ofsand-body in Yan54well-Huang73well-Huang244well in the direction from northnorth-east to south south-west is also well.But the connection in west-east profile ispoor,which the sand-body is connected only in the direction of Feng9well-Chi167well.The distribution of sand-body is from northwest to southeast as the shape of beltin the flat.The relative weakest heterogeneity of sand-body is Chang63oil formation,andthe Chang61,Chang62oil formation has a stronger heterogeneity relatively.Theheterogeneity of permeability in the inner sand-body is strong which has littledeviation,and the variation coefficient is between0.73and0.8,the dash coefficient isbetween2.83-3.21,the extreme disparity is between119.02and149.64.The maintype of interbed is muddy and calcic interbed,and the density of that is increased from Chang63oil formation to Chang61oil formation,and the value is3.20%，4.17%，4.41%respectively. The heterogeneity of intrabed is strong in Chang61oilformation,and the sand-body is isolated in space.The heterogeneity of intrabed isstrong in Chang62oil formation as well,and the sand is interbedding with clay.Theheterogeneity of intrabed is relative weak in Chang63oil formation,and thesand-body is superimposed in the vertical.According to the prediction of favorable area,the area of Feng14well andYan37well is the favorable area of Chang63oil formation,and the predicted area is188km2and365km2respectively.The area of Feng6well is the favorable area ofChang62oil formation,and the predicted area is160km2.The area of Feng11well isthe favorable area of Chang61oil formation,and the predicted area is205km2.