The Experimental Research On Displacement Effects Of Different Flooding Systems In Xingnan Oil Field

Based on the characteristic of medium-low permeability reservoirs in Xingnan Oil Field, we carried out the experiments on the evaluation of displacement effect of different chemical flooding systems in medium-low permeability artificial cores so that we can get the better flooding systems used in the medium-low permeability reservoirs for enhancing oil recovery.We determined the molecular weight of polymer based on the various permeability layers through flow characteristic experiments and the flooding system formulas through the evaluation of interfacial tension between oil and water in the formation with different surfactants, so as to carry out the experimental researches on the displacement effect of different flooding systems. The flooding systems, including single polymer flooding, non-alkali binary compound flooding, weak-alkali ternary compound flooding and strong-alkali ternary compound flooding, were carried out in the homogeneous cores and heterogeneous cores with the permeability of 300×^-3μm², 150×10^-3μm² and 50×10^-3μm² to evaluate the effect of them in order to select the proper flooding system for the medium-low permeability reservoirs in Xingnan Oil Field. The results showed the effect of binary compound flooding systems equivalent to the ternary systems' was better than that of single polymer system in the homogeneous cores. In the heterogeneous cores, the two weak-alkali ternary compound flooding systems had the same displacement effect as the two non-alkali binary compound flooding do, both of which were better than single polymer system. In the heterogeneous cores with 300×10^-3μm² and 150×10^-3μm², the displacement effect of strong-alkali ternary compound flooding ws as good as it of the systems mentioned in front, while it was worse used in the low permeability of heterogeneous cores as the poor damages to the layers from the strong-alkali.Besides, we did some researches on the evaluation of the different transit-injected time, the influences of polymer molecular weight and concentration on the recovery, the displacement effect evaluation of equiviscous systems with various concentrations in the heterogeneous artificial cores. It concluded in the following. The earlier transit-injected time was, the higher the recovery was; the higher the molecular weight was, the higher the recovery was as the better effect of viscosity-increasing under the condition of the same concentration of polymer. And the increasing enhanced not only the volume sweeping but also the displacement efficiency of the swept areas. As to the various concentrations of equiviscous systems, the recovery of ternary systems with Sy strong-alkali is as the same as that of non-alkali binary systems with BS-modified surfactant, while the recovery of the flooding systems with Ss weak-alkali is lower as the lower displacement efficency.The research will provide experiment foundations for carrying out chemical flooding to enhance oil recovery in the medium-low permeability reservoirs.