| The weak base ASP composite system of high-efficiency and low-cost is the foundation of carrying out the ASP flooding,and it is the guarantee for the reasonable prediction of its oil displacement effect.Based on the T layer in HD oilfield as research object,the comprehensive utilization of geology,performance evaluation,physical simulation experiments and other methods,with the test area,polymer and surfactant,weak base ASP performance evaluation formula system and influence factor analysis and indoor flooding effect are studied.First of all,we selected the polymer and surfactant of high-efficiency and low-cost by studying,and then carry out experimental study on the effect of physical model for weak base ASP flooding factors and indoor core performance evaluation.Finally,the weak base ASP composite system is selected suitable for the target reservoir.Through this study,the weak base ASP performance evaluation formula system,influence factor analysis and the method flow of predicting the effect of oil displacement are summed up a set of method flow.After the exact and careful research,this paper comes to the following conclusions:1.Reservoir geological development characteristics of weak base ASP test zoneAccording to the standard of chemical flooding technology and the main problems of SP flooding pilot test in HD oilfield T layer,HD5-5 well group is selected as ASP test area from the aspects of reserves abundance,remaining reserves,reservoir development,reservoir connectivity and injection well condition.Based on the HD5-5 weak base ASP test zone of reservoir characteristics,physical characteristics,heterogeneity,sedimentary characteristics and the distribution of remaining oil research,it reveals the main reservoir of the study region,TII4,TII5,TII7,TII9,TII12,TII13,TII15,TII16 contiguous development plane,and the average thickness of sandstone of the main layer TII4,TII5,TII7,TII12,TII13 of is 1-2m,and the average effective thickness is 0.5-1m,micro sedimentary facies mainly have developed in dam body and dam seats seats,meanwhile the local development of underwater distributary channel and estuary dam.The average porosity of each small layer is between 19.6%and 23.2%,and the average permeability is between 45.2×10-3?m2 and 98.6×10-3?m2.The distribution of the remaining oil in the plane is strong,showing the relatively concentrated oil well row.The remaining oil saturation of the main layers of TII4 and TII5 in different locations is less than 25%,and the remaining oil saturation of TII12 and TII13 in different locations is higher than that of TII4 and TII5,but because of the poor reservoir property of T?1 and T?3,the remaining oil are more than 35%.2.Polymer properties evaluation and its selectionThe different molecular weight of partially hydrolyzed polyacrylamide Daqing comprehensive evaluation of polymers produced in different water samples concentration,shearing,performance index of water salinity,temperature and time factors.Through this,the polymer is selected as the optimal performance and low price for T layer of HD oilfield.Performance evaluation reveals that the attenuation of polymer aqueous solution viscosity of polymer P2 and P3 have lower attenuation than that of polymer P1.The experimental results show that the polymer P2 and the polymer P3 have higher salt resistance;After shearing 60min,the polymer P2 and P3's solution viscosity retention value are higher than the viscosity of polymer P1 retention.And the polymer P2solution viscosity retention rate is 1.16 times of polymer P1 solution;and the slope and viscosity retention of polymer P3 solution are higher than that of polymer P1 solution and polymer P2 solution of the aging time.At the same time,according to the experiment of polymer displacement with different molecular weight and the experimental results of SP flooding,the relative molecular mass of mobile polymer is between 800×104 and 1000×104.And according to the physical characteristics of T reservoir in HD oilfield,the performance evaluation and injection cost factor,the best polymer P2 is used to screen out.3.Surfactant selection and weak base ASP properties evaluationBy using of JZ-2,SY-3 and TX-3 three kinds of surfactant basic performance and economic performance evaluation,which reveals the ultra low interfacial tension surfactant TX-3 in the original case compared to the other two kinds of surfactants can quickly reach 1.0×10-3mN/m,and it can be made by experiments,so the comprehensive optimization TX-3 is used as the surface active agent in weak base ASP flooding.The surfactant of TX-3 has good compatibility with formation water of HD oilfield T layer,and the formation of weak base ASP compound system is stable,which can achieve ultra-low interfacial tension below 1.0×10-3-1.0×10-4mN/m,and the emulsion emulsifying capacity by the basic weak base ASP compound system is more than 0.85,and it is conducive to the solubilization of emulsion,and then improving the recovery rate.When the polymer's concentration in the system is greater than 800mg/L,the polymer's adsorption has reached saturation,through continuing to increase the concentration of polymer solution,the polymer's adsorption losses remain unchanged;By the sand adsorption three times,interfacial tension can reach 1.0×10-3 mN/m ultra low level system;By adding a certain amount of sodium chloride and calcium chloride,the interfacial tension can still reach 1.0×10-3mN/m ultra low level.The experimental results show that the weak base ASP system of the weak adsorption capacity,anti salt and anti two ions are strong performance.4.Performance impact analysis of weak base ASPThe influence of monovalent sodium potassium ion and two valence calcium magnesium ion on viscosity and interfacial tension of three component system of weak base ASP system is studied.The experimental results show that the influence of monovalent sodium ion on viscosity of weak base ASP system is slightly larger than that of monovalent potassium ion on the viscosity of weak base ASP system.The sodium ion and potassium ion concentration and monovalent were between0.2%-3.0%,the weak base ASP system prepared under different concentration of alkali can reach below 1.0×10-3mN/m level in the ultra low interfacial tension at different time;and the calcium ion on the viscosity degree is slightly greater than that of the Mg ion impact,and the magnesium ion's influence on the interfacial tension of weak base ASP system is slightly higher than the calcium ions'influence on the interfacial tension of weak base ASP system.The experimental results show the viscosity and interfacial tension by the influence degree of different water quality on the base of weak base ASP system.The viscosity in weak base ASP system of water is 24.1mPa?s,which is the biggest;and with the increase of shearing strength,the polymer molecular weight is slowly diminished after shearing,coil size,so the volume is more easily pore throat.Experimental results reveal that the permeability of 95×10-3?m2 pore throat has little effect on the molecular weight and viscosity after shearing system;Chromatographic separation experiments show that chromatographic separation speed is the polymer>Na2CO3>the surfactant TX-3 at the same time.It requires the addition of sacrificial agent in the weak base ASP system,reducing chromatographic separation and giving full to improve oil displacement efficiency and enlarge the sweep volume of synergy in the weak base ASP system5.Experimental study on the displacement model of weak base ASPAccording to the experimental results and the actual cost of chemical flooding,the polymer main slug is recommended by 1000×104 molecular weight in the base of weak base ASP system,and the polymer's concentration is 3000mg/L,and the main slug injection volume is 0.3PV,and the concentration of surfactant is 0.3%,and the alkali concentration is 1%;through the using of water for preparation of chemical wastewater the dilution of the recovery rate of weak base ASP system is 19.74%,and the chemical waste water sewage dilution recovery rate of weak base ASP system is19.64%.The physical model experiment results show that the alkaline water for preparation of sewage diluted weak base ASP flooding recovery is higher than that of alkaline sewage wastewater diluted weak base ASP flooding recovery.And the polymer pre slug main function is to penetrate a higher profile role by reducing the adsorption loss of composite system main slug of chemical agent,so the pre slug should have certain viscosity.The experiment results show that the site using the plug injection volume is0.1PV;the subsequent protective slug is mainly for weak base ASP system of protection of weak main slug by subsequent water flooding fast break,which do not reduce the concentration of chemical agent and design.To give full play to the synergy of chemicals,enhanced oil recovery.The experiment results show that the subsequent protective slug volume is 0.15PV. |
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