## 2 Experimental
### Experimental Procedures
#### 2.3.2 Depletion Experiments of Single-Layer and Multilayer Cores  
The single-layer depletion experiments were initially conducted for the six layers with the experiment parameters tabulated in Table 1. The variations in flow rate, pressure, cumulative gas volume, and total gas production were then obtained. Subsequently, commingled simulation experiments were conducted for two layers, three layers, and four layers, respectively. The commingled two-layer experiments were conducted in three groups, utilizing the Q5 + H8, H8 + BX, and S1 + TY combinations. The commingled three-layer experiments were carried out in four groups, i.e., Q5 + S2 + TY, Q5 + H8 + S2, H8 + S2 + TY, and S2 + TY + BX combinations. The commingled four-layer production experiments were then executed in three groups, i.e., Q5 + H8 + S1 + TY, H8 + S1 + S2 + TY, and H8 + S2 + TY + BX combinations. It is worthwhile mentioning that the aforementioned experiments were conducted at an atmospheric temperature of 25 \({}^{\circ}\)C.  
The procedure of conducting commingled multilayer experiments is exemplified by the using the three-layer (i.e., Q5 + H8 + S1) scheme, i.e.,  
1. The three spliced long core plugs were placed in the three long coreholders to simulate three layers with varying petrophysical characteristics.
2. Each of the three vacuumed long core plugs were saturated separately by injecting nitrogen in a constant injection pressure mode according to the pressure of each individual layer in the targeted tight gas reservoir. The initial flow pressures of Q5, H8, and S1 were, respectively, set to be 7.30 MPa, 22.00 MPa, and 22.60 MPa to simulate gas production performance in the targeted multi-pressure tight gas reservoir.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Layer**} & **Permeability** & **Porosity** & **Pressure** & **Diameter of** & **Length of Long** & **Initial Gas** & **Abandonment** \\  & **(mD)** & **(\%)** & **(MPa)** & **Long Core (cm)** & **Core (cm)** & **Rate (mL/min)** & **Pressure (MPa)** \\ \hline Q5 & 0.76 & 8.17 & 7.30 & 2.54 & 47.40 & 2.30 & \\ H8 & 0.66 & 7.80 & 22.00 & 2.54 & 43.00 & 3.00 & \\ S1 & 0.45 & 6.05 & 22.60 & 2.54 & 42.40 & 3.70 & \\ S2 & 0.54 & 6.90 & 22.80 & 2.54 & 49.00 & 2.40 & \\ TY & 0.56 & 8.70 & 23.41 & 2.54 & 43.40 & 2.80 & \\ BX & 0.85 & 7.08 & 25.00 & 2.54 & 22.00 & 3.10 & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Experimental parameters for single-layer gas depletion and commingled multilayer production of each layer.  
During each experiment, the confining pressure was set to be 2.00 MPa higher than the initial pressure.
3. Upper experimental flow rate limit at the outlet was controlled to be the summation of each layer of 9.00 mL/min for the selected three layers by using the gas flow controller to perform constant rate depletion, simulating the commingled production in the multi-pressure system of tight sandstone gas reservoirs. When the gas flow rate could not be maintained at 9.00 mL/min, the experiment was terminated using the outlet valves, based on the abandonment pressure of 0.50 MPa.
4. The pressure, production time, and in situ gas production of each layer were monitored and recorded continuously until the end of the experiments, during which pressure at the inlet, middle, and outlet were monitored and recorded continuously.