| Since the development of the GS-N1N21 reservoir in 1990,more and more serious contradiction in the development process has been caused because of the long-term water injection and the strong heterogeneity of the formation,the main manifestation is the phenomenon of water channeling between injection and production wells,high water cut and declines in old wells.Stable production forms are not optimistic.Therefore,it is imperative to change the mode of reservoir's development in order to achieve water control and oil stabilization.Conventional weak gel are easily dehydrated at high salinity reservoir conditions,while gas flooding at reservoir conditions of strong heterogeneity is easy to form the gas channeling,the application of the above two flooding technologies to GS-N1N21 reservoir remains to be further demonstrated.Foam flooding technology uses nitrogen as its main source,nitrogen gas is abundant,easy to obtain,and has good stability.It is widely used in the oilfield.Nitrogen foam flooding technology has the advantages of combination of profile modification and oil displacement;small damage to the reservoir and wide adaptability.This article focuses on the reservoir conditions of the GS-N1N21 reservoir,combined with the current development status of the reservoir,carried out a large number of nitrogen foam chamber experiments,the mainly research results are as follows:(1)Foam volume and foam half-life were used as evaluation indicators to formulate a nitrogen foam control system formulation for GS-N1N21 high salinity reservoir:0.4%FA-3+0.2%FA-5+0.04%HYJ.The maximum foaming volume of the system under formation water conditions is 575 mL and the half-life is 95 min.The evaluation results of the foam system adaptability evaluation show that the system has good salt resistance,temperature resistance,oil sensitivity and stability.(2)Conducted experimental research on core flow in nitrogen foam system.The experimental results show that the plugging capacity is the strongest when the ratio of gas to liquid is 1:1,and the resistance factor is 65.51.The plug size combined with 0.1 PV N2+0.1PV foaming liquid has stronger sealing ability;the reasonable injection rate is 0.8mL/min;when the oil saturation of the sand filling tube is 15%,the resistance factor is reduced by about 20%compared to when the oil saturation is 0,and the decrease is not significant;when the oil saturation is greater than 35%,the resistance factor decreases by more than 70%when the oil saturation is 0.The foam system has strong sealing ability when the oil saturation is less than 15%.The nitrogen-fume double-pipe parallel core flow experiment shows that the nitrogen foam has a good profile improvement effect,the water channeling of the high-infiltration sand-fill pipe is effectively controlled,and the low-infiltration sand pipe has been started effectively,and finally the high-permeability pipe recovery efficiency increased by 14.2%,and low-permeability recovery increased by 18.3%.(3)The visualized thin sand model was designed and manufactured.This model can simulate the underground pore structure partly.Through this model,the foam generation method was observed:liquid film lagging,necking separation and film segmentation.(4)Nitrogen foam adsorption experiments were carried out.Through the static adsorption experiment of surfactants,the equilibrium temperature of the system rose from normal temperature 20? to reservoir temperature 64?,the static adsorption of FA-3 decreased from 19.1 mg/g to 14.7mg/g;As the concentration of FA-3 increases,the amount of adsorption gradually increases,and finally tends to balance.Compared with the blank control group without static adsorption experiment,the experimental group subjected to static adsorption decreased the foam oil displacement capacity by 8.28%to 17.24%and the resistance factor decreased by 2.85%to 10.14%.In the dynamic adsorption process simulated by the core flow experiment,sand-filled tubes that can be pressure-tested and sampled are used for experiments.By sampling four sampling points of the sand-filling tube,the foaming volume and half-life of the foam system are reduced.In the resistance factor analysis experiment,the resistance factors of the four sampling points at the same time are in the following order:?>?>?>?.When the displacement started,there were many adsorption sites on the surface of the quartz sand,and a large amount of surfactant was adsorbed.As the adsorption gradually became saturated,the concentration of the surfactant tended to be stable,and the resistance factors of the four sampling points also changed evenly. |
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