## 1 Introduction  
China has recently achieved notable progress in the exploration and development of tight sandstone oil, as highlighted by the discovery of several substantial tight oil reserves in the Ordos, Junggar, Songliao, and Bohai Bay basins [1]. These discoveries not only show the vast potential of tight oil resources in China [1] but also drive innovation in exploration and development technologies for tight sandstone reservoirs. Tight oil reservoirs are typically classified based on their petrophysical properties, specifically those with permeability below 0.1 mD and porosity below 10% [2]. Tight sandstone reservoirs have generally undergone intense diagenesis, mainly characterized by strong compaction, cementation, and dissolution, resulting in low porosity and permeability [3]. They are further characterized by poor petrophysical properties, complex pore structures, and pronounced heterogeneities [4]. Due to poor permeability and low production capacity, reservoir stimulation is often required to achieve an industrial oil flow rate [5]. The low permeability of tight oil reservoirs causes significantly higher capillary resistance compared with conventional reservoirs, with oil migration and accumulation largely governed by buoyancy and capillary forces [6]. According to the Washburn equation [7], capillary forces are primarily determined by pore-throat radius, oil-water interfacial tension, and fluid-rock interactions or reservoir wettability within the reservoir [8]. Therefore, pore structure and wettability are pivotal in determining oil and gas mobility within tight oil reservoirs, making research into these characteristics essential for enhancing oil recovery. Within our study area, the pore structure of the Shahejie Formation reservoirs in the Bohai Bay Basin has been extensively studied; however, there is still a lack of systematic research on the reservoir wettability characteristics in the lower Es4 tight sandstone reservoirs, hampering tight oil production. Wettability denotes the tendency of a fluid phase in a multiphase system to spread over or adsorb onto a solid surface [9; 10]. As a fundamental property of tight sandstone reservoirs, wettability governs both the distribution of reservoir fluids within porous media and the flow behavior of oil and water [11]. The in-depth study of wettability and its influencing factors is crucial for refining enhanced oil recovery techniques, such as water/surfactant/CO\({}_{2}\) flooding, and for predicting reservoir dynamics, evaluating development prospects, and formulating effective extraction strategies. Tight sandstone reservoir rocks develop extensive micro- and nano-scale pores and throats, within which the influence of wettability on oil-water flow is particularly pronounced, increasing the complexity of fluid distribution and migration pathways [12]. Therefore, the accurate characterization of wettability is essential for enhancing oil extraction efficiency and prolonging the economic lifespan of oil reservoirs. The heterogeneity of the pore structure in tight sandstone reservoirs, coupled with the complex relationships among various minerals, renders the assessment of wettability particularly challenging. This is further complicated by the scarcity of specific techniques for characterizing wettability within micro- and nano-scale pores and a lack of research on the mechanisms of oil-water retention [13]. Currently, the standard methods for evaluating rock wettability include the Amott test, the United States Bureau of Mines (USBM) test, spontaneous imbibition (SI), contact angle (CA) measurements, Nuclear Magnetic Resonance (NMR) experiment, Environmental Scanning Electron Microscopy (ESEM) for in situ observation, and molecular dynamics simulation [14]. Due to their small pore-throat sizes as well as low porosity and low permeability of tight oil reservoirs, indirect measurement methods such as the Amott and USBM tests, which rely on displacement processes, often struggle to achieve accurate results [15].