## 2 Research Materials and Methods
### Research Methods  
In this paper, scanning electron microscopy, X-ray diffraction and core casting thin section experiments were used to analyze the core of tight sandstone:  
1. Scanning electron microscope experimental analysis: It was performed mainly to obtain the micromorphology of core samples by electron signal imaging. SEM experimental analysis involves using a scanning electron microscope (SEM) to examine core samples. The process includes several key steps: preparing samples to ensure they have smooth and conductive surfaces; loading them onto the SEM stage; directing an electron beam onto the sample surface; collecting signals using detectors; processing the signals to enhance image clarity; and analyzing the images to identify microstructural features such as particle size, shape and arrangement. This method facilitates the acquisition of crucial information regarding sample composition, structure and porosity properties through quantitative or qualitative evaluations.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Title** & **Well** & **Depth (m)** \\ \hline \multirow{2}{*}{Cast thin section experiment} & W9 & 751.55 \\ \cline{2-3}  & H4 & 761.25 \\ \hline \multirow{2}{*}{SEM experiment} & C19 & 840.47 \\ \cline{2-3}  & C88 & 864.77 \\ \hline \multirow{2}{*}{X-ray diffraction experiment} & Q41 & 875.47 \\ \cline{2-3}  & X208 & 793.69 \\ \cline{2-3}  & D38 & 809.43 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Sample information for experiments.  
2. X-ray diffraction experimental analysis: This experiment aimed to utilize X-ray diffraction to analyze the mineral content of rock samples. Initially, the samples undergo meticulous preparation before being loaded into the instrument. Subsequently, X-rays are used to irradiate the samples, and the resulting diffraction patterns are recorded and analyzed for peak positions and intensities. Analysis of peak positions allows inference of each sample's crystal structure. Moreover, peak intensity correlates positively with mineral content, enabling quantitative analysis of different minerals' content in the sample. Ultimately, thorough analysis of the diffraction patterns and interpretation of quantitative data yield precise estimations of mineral content in the samples, facilitating in-depth discussions regarding their geological significance.
3. Rock casting thin section analysis: Rock thin section casting analysis involves several key steps. Firstly, thin sections are meticulously prepared from rock samples and then meticulously imaged under an electron microscope. The electron signals emitted from each sample's surface are meticulously recorded and thoroughly processed to extract detailed information regarding its microstructure and chemical composition. Subsequently, these thoroughly processed signals undergo meticulous morphological and compositional analysis to accurately identify the rock type. This is followed by a careful comparative analysis with other samples to precisely delineate their differences and characteristics. Through meticulous signal processing via electron beam spots, the rock type of the Yanchang Formation reservoir in Ordos could be precisely determined, facilitating in-depth comparison and analysis of the characteristics of tight oil reservoirs.