## 3 Materials and Methods  
All the samples were analyzed at the Laboratory of Wuhan Xinshengji Technology Co., Ltd. Whole-rock X-ray diffraction (XRD) analyses were performed on 120 shale samples collected from depths of 1215.9-1255.15 m in the well using a SmartLab SE X-ray diffractometer (Rigaku) operating at 40 kV and 40 mA, according to the national standard SY/T 5163-2018. Twenty-six samples from depths of 1215.9-1252.95 m were selected for organic geochemical analyses: TOC analyses were performed on all 26 samples using a TOC-L CPH SM5000 analyzer (Shimadzu) following the national standard GB/T19145-2003,  
Figure 2: Comprehensive stratigraphic column of the upper Permian Dalong Formation in well ED-2.  
analyses were performed on 20 of the 26 samples using an MPM-80 stereomicroscope (Leica) according to the national standard SY/T5124-2012, and the microstructure of kerogen was investigated in all 26 samples using a DMLD microscope (Leica) following the national standard SY/T 5125-1996.  
We assessed three aspects of the shale reservoirs: shale total porosity and permeability, shale pore structure, and shale adsorption capacity. Shale total porosity and permeability were analyzed in 18 samples collected from 1215.9-1256.35 m depth in the well using a KXD-II combined porosity and permeability meter manufactured by Huaxing Petroleum Devices Co., Ltd., following the national standard GB/T 29172-2012. Eleven samples were selected from depths of 1215.9-1252.9 m in the well for shale pore structure characterization. Six of those eleven samples were used to analyze pore types in the Dalong Formation shales qualitatively; after polishing using an argon ion beam, the nano-microscale pores on the polished surfaces were directly observed by secondary electron imaging using an EVO LS15 SEM (Zeiss). The other seven samples were subjected to CO\({}_{2}\) and N\({}_{2}\) adsorption tests to quantify their pore structures. Low-temperature and low-pressure CO\({}_{2}\) and N\({}_{2}\) adsorption tests were performed using an Autosorb iQ3 volumetric adsorption analyzer (Quantachrome). In the first adsorption test, we used CO\({}_{2}\) as the adsorbate to determine adsorption under different relative pressures, which refers to test pressure/saturated steam pressure (\(P/P_{0}\)) in the range of 0-0.03. The density functional theory (DFT) model was applied to process the data and obtain micropore volumes and specific surface areas. For N\({}_{2}\) adsorption tests, the adsorption and desorption of N\({}_{2}\) under different pressures were measured at the temperature of liquid N\({}_{2}\) (77.4 K), and the Barret-Joyner-Halenda (BJH) model was adopted to calculate pore volumes and specific surface areas. The shale adsorption capacity was determined by isothermal methane adsorption experiments using seven representative samples with evenly distributed TOC contents from depths of 1215.9-1249.2 m in the well. These samples were from the same horizons as those selected for gas adsorption tests and were used to analyze the influence of pore structure parameters on shale adsorption capacity. A high-pressure magnetic suspension balance-based gravimetric adsorption analyzer was used for the experiments, and methane adsorption by the shale samples was measured under a constant temperature of 30 \({}^{\circ}\)C in the pressure range 0-32 MPa.