## 5 Conclusions  
The research method, which combines a physical experiment with digital core methods, can greatly shorten the experimental period. In addition, after verifying the accuracy of the 3D digital core, the scale shape and production system of the research object can be arbitrarily changed. By this way, the approach greatly increases the flexibility of the research and all of them complete the experiment in a short period. This promising research method is applied to the matrix failure process of tight reservoirs, which can reveal the seepage mechanism of a tight sandstone reservoir as follows.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Order**Factor & **Pressure (MPa)** & **Viscosity** & **Permeability** & **Length** & **Time** & **Recovery** \\  & **(MPa-s)** & **(mD)** & **(cm)** & **(h)** & **(\%)** \\ \hline
1 & 10 & 0.6 & 0.075 & 3.25 & 2.5 & 3.27 \\
2 & 10 & 1.2 & 0.15 & 6.5 & 5 & 3.29 \\
3 & 10 & 1.8 & 0.225 & 9.75 & 7.5 & 3.13 \\
4 & 10 & 2.4 & 0.3 & 13 & 10 & 2.87 \\
5 & 20 & 0.6 & 0.15 & 9.75 & 10 & 6.06 \\
6 & 20 & 1.2 & 0.075 & 13 & 7.5 & 3.79 \\
7 & 20 & 1.8 & 0.3 & 3.25 & 5 & 15.54 \\
8 & 20 & 2.4 & 0.225 & 6.5 & 2.5 & 5.39 \\
9 & 30 & 0.6 & 0.225 & 13 & 5 & 9.96 \\
10 & 30 & 1.2 & 0.3 & 9.75 & 2.5 & 9.96 \\
11 & 30 & 1.8 & 0.075 & 6.5 & 10 & 9.03 \\
12 & 30 & 2.4 & 0.15 & 3.25 & 7.5 & 15.51 \\
13 & 40 & 0.6 & 0.3 & 6.5 & 7.5 & 13.16 \\
14 & 40 & 1.2 & 0.225 & 3.25 & 10 & 12.99 \\
15 & 40 & 1.8 & 0.15 & 13 & 2.5 & 9.29 \\
16 & 40 & 2.4 & 0.075 & 9.75 & 5 & 8.64 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Orthogonal test calculation results.  
Figure 8: Micro-crack state under different pressures. (**a**) Low pressure, and (**b**) high pressure.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Level**Factor & **Pressure (MPa)** & **Viscosity (mPa-s)** & **Permeability (mD)** & **Length (m)** & **Time (h)** \\ \hline
1 & 3.14 & 8.1125 & 6.1825 & 11.8275 & 6.9775 \\
2 & 7.695 & 7.5075 & 8.5375 & 7.7175 & 9.3575 \\
3 & 11.115 & 9.2475 & 7.8675 & 6.9475 & 8.8975 \\
4 & 11.02 & 8.1025 & 10.3825 & 6.4775 & 7.7375 \\ Difference & 7.975 & 1.135 & 4.2 & 5.35 & 2.3(1) The macroscopic starting pressure gradient is embodied in the microscopic pore structure. Under the lower exhaustion pressure difference, part of the micro-crack is in the closed state. When the pressure rises, the crack reopens, thereby, increasing the conductivity of the reservoir.  
(2) Considering the time scale, the core recovery is analyzed by the orthogonal test. Then the factors, in order of importance, are pressure, length, permeability, time, and viscosity.  
Conceptualization, H.W.; Formal analysis, X.D.; Investigation, Z.S.; Methodology, X.D.; Project administration, G.X.; Writing--original draft, Y.X.; Writing--review & editing, Y.W. All authors have read and agreed to the published version of the manuscript.  
The work was supported, in part, by the National Natural Science Foundation of China under Grants U19B2029, 61872365, 61773382, 61773381, and U1909204, CAS Key Technology Talent Program (Zhen Shen), and Hunan Province Science and Technology Program under Grants 2018 GK1040.  
Not applicable.  
All data generated or analyzed during this study are included in this manuscript.  
The authors declare no conflict of interest