The Evolution Law of Wettability Degree After Energy Replenishment in Tight Type-II Reservoirs with Different Pore Structures

Tight oil is an important resource replacement in the petroleum industry, with the reserves of Type-II energy accounting for over 40%. However, these reservoirs have small pore throats and complex structures, and their wettability directly affects the EOR by affecting the occurrence of crude oil and multiphase flow mechanisms. In response to an unclear understanding of the evolution mechanism of wettability after energy replenishment in tight reservoirs with different reservoir formation conditions, the evolution law of wettability in different energy replenishment media for tight type-II reservoirs is evaluated by performing wettability experiments and nuclear magnetic resonance experiments, and the mechanism of differential changes in wettability after energy replenishment in different media is elucidated. The results show that the block with well-developed pores and good connectivity (Block: Z401) had the smallest in situ wetting angle, ranging from 27.1° to 30.4°, and that the interface effect had a small impact, resulting in a small change in the wetting angle after energy replenishment. The wetting angle of the developmental intersection block (Block: G93) is the highest, ranging from 36.6° to 46.4°. The connected pore and throats fully interact with the medium at the interface, resulting in a significant change in the wetting angle. In addition, after natural gas energy supplementation, the principle of similar solubility causes a significant change in the wetting angle of the pore throat interface after adsorption, with a maximum angle of 19.6°. The change in the wetting angle change of the CO2 mixed-phase principle is in the middle, at about 13.6°, while the change in the wetting angle is minimal after N2 replenishment, around 10°. The research results improve our understanding of the basic theory of tight oil supplementary energy development and have important practical significance.