Construction of Wetting Inversion System and Evaluation of Oil Enrichment Performance

Reservoir wettability is an important factor affecting the degree of crude oil recovery, and achieving wetting inversion on the rock wall is beneficial for subsequent water drive to improve recovery. In this paper, the ability of five cationic surfactants to change the reservoir wettability was evaluated for the specific reservoir physical conditions in the Shengli oilfield, and the optimal wettability reversal system from hydrophilic to oleophilic was constructed using the oil-water-solid three-phase contact angle as an indicator. On this basis, the influence of the wetting inversion system on the recovery enhancement of the subsequent water drive was quantitatively described by sand-filling physical simulation experiments. The experimental results show that the subsequent water drive again shows a significant pressure peak, and the pressure drop rate after the injection water breakthrough is significantly smaller than that of the primary water drive. In addition, the recovery rate of the secondary water drive increased by 24.6%, which had a significant oil enhancement effect. The study provides theoretical guidance for the effective development of sandstone reservoirs and similar types of reservoirs in Shengli Oilfield.