Abstract: At the very beginning there were 42 deviation wells in River 50 cluster wells. To tap the potential of residual oil, 35 infilled wells were spaced again. In view of the difficulties, the reinforced low-density foam cement slurry, the low-density cement slurry with micro-silicon and floating beads, the toughness-enhancing cement slurry with low-fluid loss and micro-expansion, the technology of turning mud cakes into gel cakes, and the full rubber external casing packer are selected to assure cementing quality, which have been applied to 30 wells in River 50 Block. Low-density cement slurry is applied to the upper part of the oil layer, while the toughness-enhancing cement slurry with low-fluid loss and micro-expansion is used in all oil layers. Cement goes back to the wellhead, and the slurry cementing section ranges from 2065 m to 3125 m. Cementing is achieved in all wells, and no leakage occurred. Variable density log shows that well quality qualified ratio reaches 100%, and quality rate is 79% which increases by 12% as compared with the adjustment wells in adjacent blocks.