| Area X of Wuqi oilfield is located in the western middle section of Yishan slope in Ordos Basin.It is a low porosity and low permeability reservoir with strong heterogeneity.After long-term water injection development,the water breakthrough of oil wells is too fast,the comprehensive water cut is high,and the crude oil recovery is low.In order to improve the crude oil recovery,first of all,polymer nanospheres are used to block the high permeability large channels away far from oil well section in the reservoir and then modified silica nanospheres are used to adjust the near well reservoir.Making full use of the characteristics of soft elasticity and deformability of polymer nanospheres,which can plug the deep large pore throat and improve the water injection sweeping volume,what's more,The near well reservoir is adjusted by taking advantage of the characteristics of high strength and low oil-water interfacial tension of modified silica nanospheres,which improve the oil washing efficiency of injection water.The oil recovery of low permeability oil field can be improved by two kinds of nano microspheres compound flooding.The polymerization nanospheres were synthesized by inverse microemulsion polymerization.By optimizing the synthesis conditions,the components of microemulsion were determined as follows:oil phase(No.5 white oil)43.16wt%,emulsifier(Span80:Tween80=3:1)18.38wt%,water phase(acrylamide monomer concentration 40wt%,AMPS10wt%,N,N'-methylene bis acrylamide 0.05wt%)38.46wt%;the best reaction condition were as follows:stirring speed 500?800rpm,The initial reaction temperature 35?,initiator dosage(molar ratio of ammonium persulfate to sodium bisulfite 1.1:1)0.55%of aqueous solution,reaction time 2 hours,finally the structure and properties of the synthesized products were characterized.Silane coupling agent was used to modify silica.The silane coupling agent with carbon atom 9(3-glycidyl oxypropyltrimethoxysilane)was selected,and the dosage was 6%of silica.The silane coupling agent was hydrolyzed in alcohol water mixture(absolute ethanol:Deionized water=9:1),and the silica was mixed with distilled water to form the emulsion,then the silane coupling that has been hydrolyzed was mixed with silica emulsion,they reacted with each other for 2 hours at the degree of 85 celsius,and after that,the modified silica nanospheres were created,and the structural characterization and performance evaluation of the modified silica nanospheres were carried out.High and low permeability artificial core(one permeability is 500×10-3?m2,the other is 5×10-3?m2,simulating high and low permeability reservoir)is used to simulate heterogeneity of reservoir.Through core physical model oil displacement experiment,the composite flooding slug of polymer nanospheres and modified silica nanospheres is optimized.The results show that:0.30%polymer nanospheres injected 0.30pv,then 0.30%modified silica nanospheres injected 0.30pv,which enhanced oil recovery by 23.0%;compared with the same injection amount of polymer nanospheres,which enhanced oil recovery by 10%;compared with the same injection amount of modified silica nanospheres,which enhanced oil recovery by 17.8%;it shows that the effect of composite flooding with nanospheres is better than that of single flooding.Well group Y in area X of Wuqi oilfield was selected for field test.After construction,the daily oil production increased from 5.94t/d to 6.95t/d,the daily oil production increased by17%,the comprehensive water cut decreased from 70.03%to 56.58%,and decreased by13.45%.The nano microsphere composite flooding system can effectively improve the crude oil recovery. |
PDF Full Text Request