## 3 Samples and Experimental Methods
### Pore Structure Characterization Experiments
HPMI experiment applies external pressure to a core plug to make mercury overcome the non-wetting interfacial tension and enter the pores, thereby quantitatively acquiring key parameters such as pore size distribution, pore volume, and capillary pressure curves, providing a direct basis for the quantitative characterization of the reservoir pore structures [46]. Analysis of mercury withdrawal efficiency and the plateau morphology of the capillary pressure curve further allows qualitative assessment of pore-throat network connectivity, providing a basis for evaluating reservoir flow continuity. The injection pressure and pore radius in the mercury intrusion experiment satisfied the Washburn equation [47]. In this study, HPMI was conducted on 13 core plugs with various reservoirs (5 core plugs with turbidite sandstone and 8 core plugs with delta front sandstone) via an AutoPore IV9500 mercury intrusion porosimeter (Micromerities Instrument Corporation, Norcross, GA, USA). The mercury intrusion tests included both pressurized intrusion and pressurized withdrawal tests, with a maximum experimental pressure of 200 MPa. In all cases, the experimental data were collected using a reference intrusion equilibration rate of at least 0.001 uL/g/s. NMR is a physical process in which atomic nuclei with non-zero magnetic moments split their spin energy levels under the influence of an external magnetic field and absorb radiofrequency radiation of a certain frequency to enter a higher energy state [48]. After the radiofrequency pulse ceases, under the influence of the main magnetic field, the transverse macroscopic magnetization vector gradually decreases to zero, corresponding to the transverse relaxation time. For the same fluid properties and rock sample, the relaxation time is determined by the pore size. Tight sandstone exhibits three relaxation mechanisms: particle surface, bulk fluid, and molecular diffusion relaxation. The relaxation time of bulk fluid and molecular diffusion becomes negligible when the samples are saturated with water, allowing the relaxation time \(T_{2}\) to be simplified to Equation (1) [49; 50; 51]. \[\frac{1}{T_{2}}=\rho_{2}\frac{S}{V} \tag{1}\]In Equation (1), \(T_{2}\) (ms) represents the surface relaxation time, \(S/V\) (\(\upmu\)m\({}^{-1}\)) denotes the specific surface area, and \(\rho_{2}\) (\(\upmu\)m/ms) represents the surface relaxation rate. From Equation (1), it can be seen that \(T_{2}\) is related to the specific surface area \(S/V\) of a single pore. Let the value of \(S/V\) be equal to the value of \(F_{S}/r\), then we have  
\[T_{2}=\frac{r}{\rho_{2}F_{s}} \tag{2}\]  
In Equation (2), \(T_{2}\) (ms) represents the surface relaxation time, \(\rho_{2}\) (\(\upmu\)m/ms) represents the surface relaxation rate, \(r\) (\(\upmu\)m) denotes the pore radius in micrometers, and \(F_{S}\) denotes the shape factor of a pore, which is related to the geometric shape of the pore. From Equation (2), it can be seen that the transverse relaxation time \(T_{2}\) is theoretically linearly proportional to the pore radius. Therefore, the NMR \(T_{2}\) spectra can be converted into the pore-throat radius distribution curve [46; 52; 53; 54]. In this study, the MicroMR12-040 V equipment of Jiangsu Newman Company was used for NMR, the coil diameter of the instrument probe was 10 mm, and the average working environment was controlled at 22 \({}^{\circ}\)C-28 \({}^{\circ}\)C. The following parameters are set for the device: the sampling frequency is 200 kHz, the number of echoes is 6000, the number of scans is 16, the waiting time is 1000 ms, and the echo interval is 0.1 ms.