| The problem of insufficient injection in water injector is common in the low permeability blocks of Binnan oilfield.The Bin 649 block is a typical low permeability reservoir in Binnan oilfield.So it's necessary to clear understanding its low permeability properties and production characteristics of waterflooding.The low permeability properties of the reservoir were analyzed by using X-ray diffraction?XRD?,scanning electron microscopy?SEM?,energy spectrum analysis?ESA?,laser confocal scanning microscope?LCSM?,casting thin sections?CTS?,nuclear magnetic resonance?NMR?and four-cylinder piston pump?FCPP?.And combined with analysing the data of the geology and production dynamic of the oilfield,the production characteristics of waterflooding in Bin 649 block were evaluated.The reservoir porosity is concentrated within 12.43%to 13.53%with an average of13.06%,and the permeability is mainly between 8.84×10-3?m2 and 31.20×10-3?m2 with an average of 19.36×10-3?m2;It belongs to low porosity and low permeability reservoir.XRD results showed that quartz and feldspar were the main minerals,accounting for 33.9%and 32.9%,respectively;Clay minerals account for about 3.7%,of which illite/smectite account for 48%and illite account for 37%.SEM and ESA results demonstrated that the panorama was fine grained sandstone,and the clastic grain size was mainly between 100?m and 180?m;The weathering degree of the feldspar was deep,which formed clay minerals and intragranular porosity.LCSM results displyed that the heterogeneity of pore distribution was stronger.CTS combined with NMR results confirmed that the throat radius was mainly distributed between 0.29?m and 0.55?m;The necking throat was the main throat type,and the pore throat ratio was concentrated within 36.2 to 67.9.The determination results of the movable fluid by NMR showed that movable fluid percentage was between 26.02%and 65.67%with the average value was 47.83%.FCPP results demonstrated that the starting pressure gradient was between 0.005MPa/m and0.018MPa/m with the average value was 0.0097MPa/m.The evaluation of production dynamic of water well showed that due to throat radius is small and starting pressure gradient is relatively high,the layers of ideal water absorption only account for 15%,the formation pressure showed linear decrease,and the decrease rate per year was 0.48MPa.The analysis of decline type of water injection well diplayed that due to clay minerals are mainly water sensitive mineral illite,there were different degrees of damage in each operation method;The results showed linear decrease after well washing,stopping waterflooding and new injection,and decline model of acidification and fracturing was cubic polynomials,and conversion well generally comply with quadratic polynomial decline model.Study on the decline law of oilfield production showed that the productivity index per meter of the oilfield was concentrated within 0.06t/?d·MPa·m?to0.1t/?d·MPa·m?,the productivity of the oil reservoir was low,production declines exponentially with fine,and the decline rate was 8.9%.Potential analysis showed that due to reservoir minerals are dominated by feldspar with strong solid-liquid adsorption,recovery factor was only 27.6%,and the development potential of irreducible fluid was large;Due to the porous body has stronger heterogeneity,the degree of mobilization in each small layer was quite different,and the subdivision layer system had a greater potential to increase the degree of vertical storage utilization.The results of studying on the low permeability properties and production characteristics of waterflooding in Bin 649 block that provided an evidence for making under-injection countermeasures and deploying oil reservoir development scheme of the next step in Binnan oilfield. |
PDF Full Text Request