The SD107 gel system developed has good oil−water phase selective gelation and oil−water phase selective blocking properties. The static gel-forming experiment results showed that the gel water shutoff system formulated with oilfield reinjection water (oil content < 0.05%) has a viscosity of 200 mPa·s after gelation, and the gel water plugging system formulated with oilfield produced fluid (oil content ≥ 20.0%) had a viscosity of 26 mPa·s after gelation. Results of the core physical simulation experiment indicated that the enhanced recovery rate was the highest (34.6%) when the resistance ratio of the high-low permeability core was about 10.0 after plugging. As per the fluid volume (Q) of the oil well to be blocked, the maximum production pressure difference (∆P) was predicted, and on the basis of economic output, the resistance of the oil section, the resistance of the high water cut section, and the resistance of the water outlet section after plugging was used to calculate the plugging depth (re1, the limit water plugging radius), which offers a basis for the design of water plugging process parameters for horizontal wells. The field water plugging test results showed that after using this water plugging technology, the daily oil production increased from about 4 t/d to 20 t/d, the daily oil increase was 16 t/d, and the water cut decreased from 75% to about 25%. The water-blocking construction was a success.