Interface Modifiers for Shale Oil Reservoir Protection and Their Blockage Removal Mechanism

Abstract

The shale oil reservoirs of the Lianggaoshan Formation in the Jurassic system are characterized by low porosity, low permeability, and strong heterogeneity. In addition, the crude oil exhibits high viscosity and poor mobility, which leads to residual oil entrapment and pore blockage, thereby severely limiting the oil recovery efficiency. To effectively alleviate pore-scale oil blockage and protect the reservoir, this study investigates two interfacial modifiers, WPM-1 and WPM-2, aiming to systematically evaluate and select a highly efficient modifier suitable for the shale oil reservoir and determine its optimal concentration. First, the basic interfacial performance of the two interfacial modifiers was evaluated through compatibility tests, interfacial tension measurements, and wettability experiments. On this basis, the entropy-weighted TOPSIS method was introduced, and a multidimensional evaluation index system was established to construct an optimal concentration selection model, whereby the optimal dosage for both systems was determined to be 2%. Subsequently, emulsification performance evaluation experiments and nuclear magnetic resonance (NMR) flooding experiments were conducted. Based on these experiments, the microscale oil mobilization characteristics and the mechanisms of oil blockage removal under the action of interfacial modifiers were analyzed. The results indicate that WPM-1 exhibits superior interfacial regulation capability and better reservoir compatibility. NMR analysis shows that the pore structure is characterized by “mesopores as the dominant component, macropores as a supplement, and micropores being negligible.” Mesopores contribute the most to crude oil mobilization, accounting for up to 79.1%, while the contributions of macropores and micropores are relatively limited. The flooding process can be divided into an early stage rapid imbibition phase and a late-stage slow production enhancement phase. The interfacial modifiers synergistically promote oil mobilization and alleviate pore blockage through multiple mechanisms, including interfacial tension reduction, wettability alteration, imbibition displacement, and emulsification-assisted transport, thereby enhancing oil recovery and protecting the reservoir.