Research On Technique Of In Depth Fluid Diversion And Its Reservoir Adaptation

At present,many oil fields in the eastern part of China entered high or ultra-high water cut stage.The waterflooding effect was unfavorable due to inefficient circling of injected water in the high permeable layers.Therefore,there was an urgent need to carry out fluid diversion technique to enlarge the swept volume and improve the flooding effect.For the needs of oilfields,a great deal of researches were carried out on performance characteristics,profile control and displacement effect,reasonable slug combination,and compatibility with specific reservoir of amphoteric cross-linking polymer solution/gel,swelling particles,soft microgel(SMG),inorganic gel coating(OMGL).Based on physical chemistry,polymer materials science,and reservoir engineering,by means of instrument detection,chemical analysis,physical modeling,the resistance factor(FR),residual resistance factor(FRR),diversion rate,and recovery efficiency were tested.The coreflooding tests indicated that the value of "average pore radius/molecular coil dimension" was 3.92-9.43(the molecular coil dimension was coil gyration radius RG),5.69-13.50(the molecular coil dimension was hydrodynamics radius Rh),or 4.74-11.29(the molecular coil dimension was root mean square gyration radius Rg)of amphoteric crosslinking polymer solution.The swelling particle was of 1.01-1.39.The SMG(W)was of 1.05-1.29 and SMG(Y)was of 0.59-0.63.There was reasonable matching relation between concentration combination of OMGL solution and Ca2+solution and core permeability,which was useful for agent concentration optimization.The crosslinking reaction hardly occurred in porous medium during the migration of amphoteric polymer solution.However,the intramolecular crosslinking reaction occurred after standing for some time.Swelling particles was of migration ability in reservoir before absorbing water.The increase in pressure indicated the fluid diversion ability at later subsequent water flooding stage,due to particle swelling after water adsorption.SMG particles could swell in the porous medium during its migration,which can generate better fluid diversion effect.The inorganic gel coating generated when OMGL solution and CaCl2 solution was injected alternatively,which can reduce the pore area,increase the flow resistance,and change the subsequent injected water direction.To three-layer heterogeneous cores,when the permeability variation factor was 0.25,0.59,and 0.72,respectively,the reasonable permeability of amphoteric crosslinking polymer solution/gel(CP=2500mg/L,Ccrosslinking agent=0.2%)ranged from 1100×10-3 ?m2 to 2850×10-3 ?m2,900×10-3 ?m2 to 2650×10-3 ?m2,and 750×10-3 ?m2 to 2500×10-3 ?m2.The reasonable permeability of swelling particles(particle size 200,mass concentration 0.5%)range from 26400×10-3?m2 to 36100×10-3 ?m2,25300×10-3 ?m2 to 35000×10-3 ?m2,and 24300×10-3 ?m2 to 34000×10-3 ?m2.The reasonable permeability of SMG(particle size 7?m,mass concentration 0.3%)ranged from 2240×10-3?m2 to 3760×10-3 ?m2,2100×10-3 ?m2 to 3620×10-?m2,and 1960×10-3 ?m2 to 3480×10-3 ?m2.The reasonable permeability of inorganic gel coating OMGL(mass concentration 1.35%)ranged from 590×10-3 ?m2 to 1790×10-3 ?m2,500×10-3 ?m2 to 1700×10-3 ?m2,and 400×10?m2 to 1600×10-3?m2.Therefore,compared with single diversion agent flooding,reasonable combination of diversion agents was more beneficial to improving recovery efficiency.The single diversion agent was not suitable for blocking ultra high permeable layer or big pore throat when the reservoir condition was complicated.The synergy effects occurred when kinds of diversion agents injected reasonably.Therefore,the subsequent injected fluids were inclined to enter middle or low permeable layers.