## 3 Sampling and Testing Methods  
In this study, rock samples were collected from the core data of 23 wells. A total of 351 cast thin sections were analyzed, including 123 drilling core samples, 81 wall core samples, and 147 broken samples. MSR samples covered the A3, B1, B2, B3, and B4 sub-layers. Five methods were used in this study, and the details of the samples are shown in Table 1.  
The pathological analysis was mainly performed using a microscope. The granularity of sandstone was measured under the microscope using dot notation. Combined with image analysis, the statistical error of granularity was found to be less than 8%. The crystal size of dolomite was also determined using the same method.  
Fourteen samples were selected for element measurement, including two sandstones bearing dolomite, three dolomitic sandstones, four dolostones bearing sand, and five sandy dolostones. The samples were crushed into 80-100 mesh. After resolution, 9 major elements (e.g., Al, Fe, Mn) were measured using the PE 5300 V inductively coupled plasma atomic emission spectrometer (ICP-OES). Forty-five trace elements (e.g., V, Ni, Rb) were measured using the Agilent 7700 series ICP-MS at the State Key Laboratory of Oil and Gas Reservoir Geological Development in China. The standard for the experimental test followed the GB/T14506-2010 [30], part 29 (Chinese national standard). Fourteen bulk sample powders were dried in equal parts (100 mg each) at 100 \({}^{\circ}\)C for 2 hours and dissolved in a mixed solution consisting of 4 mL hydrofluoric acid, 2 mL hydrochloric acid, 3 mL nitric acid, 1 mL perchloric acid, and three drops of sulfuric acid. The sample dissolved in the solution was then heated to approximately 200 \({}^{\circ}\)C for 4 hours until white smoke was produced. Next, 5 mL of chlorazic acid was added to the solution to extract the elements. The solution was then transferred to a 50 mL volumetric flask and diluted to volume with deionized water. The main elements were determined by ICP-AES, and the trace element was determined by ICP-MS.  
Thirty-one samples of MSRs and dolostones were analyzed by X-ray diffraction (Rigaku XRD/Rigaku Ultima IV), with only four samples containing clay minerals, with content distribution between 1.5 and 10%. The clay mineral type was mainly illite, with a small amount of Aemon mixed-layer minerals.  
The porosity and permeability tests for 81 wall cores were conducted in the same laboratory using the gas method. The relative deviation of porosity was 0.5-1.5%, and for permeability, it was \(\leq\)10% for low permeability samples.  
To evaluate the mixing degree in both the vertical and lateral directions, a quantitative mineral interpretation of logging data well using the Elan model was performed after calibration with the XRD result. After interpretation, the types of mixing rocks were determined based on the relative content of sandy and cloudy materials, and the mixing degree was further calculated.  
\begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Testing Method** & **Sample Quantity** \\ \hline
1 & cast thin sections & 351 \\ \hline
2 & grading analysis & \\ \hline
3 & element measurement & 14 \\ \hline
4 & X-ray diffraction & 31 \\ \hline
5 & porosity and permeability test & 81 \\ \hline \end{tabular}
\end{table}
Table 1: The sample information in the study.