## 2 Experimental Preparation
### Test Procedure  
In hydraulic fracturing experiments, prior to the start, an epoxy resin high-temperature-resistant sealant is used to fill the gap between the steel wellbore and the wellbore wall, achieving a sealing effect, as shown in Figure 3a. In the case of deflagration fracturing, there is no wellbore, necessitating a different approach for hole treatment. Before the experiment, a specific amount of deflagration agent is wrapped in a waterproof membrane and placed inside a paper cylinder that matches the diameter of the borehole. This paper cylinder is then fixed at the bottom of the borehole, while the upper section of the borehole  
Figure 2: Processing of the large-sized sample. (**a**) Drilling of granite sample, (**b**) processed granite sample.  
is sealed with thermally conductive potting adhesive to create an enclosed space inside the paper cylinder. The wires from the igniter are routed through the sealed section.  
Then, the rock samples with the wellbores sealed are placed inside the experimental device, and the heating plate, insulation plate, and loading device are placed in sequence. Meanwhile, the fluid injection pipes or the wires for ignition are connected properly. Finally, the top cover is installed and the pressure-bearing nuts are tightened to ensure the overall rigidity of the device.  
Next, the rock sample is subjected to temperature and axial force to ensure that it satisfies the preset test conditions, following the principle of \"heating first, then applying force\". Given the relatively large size of the rock sample, in order to ensure effective heating throughout its interior, it is necessary to heat it for at least 8 h. After reaching the target temperature, silicone oil is injected into the stainless steel pressure container by a hand-operated pump to achieve the axial loading. The pressure sensor connected to the container can be transformed into the axial stress value.  
Finally, two parallel-connected ISCO pumps are used to continuously inject water into the wellbore at a constant flow rate, achieving hydraulic fracturing of the rock sample. The test is terminated when the fluid pressure within the wellbore drops to a lower value or water flows out of the device. As for the deflagration fracturing, this is achieved through an ignitor. When the switch is pressed, a high-voltage current is transmitted through the wire to the deflagration agent and causes it to undergo a phase change and release a large amount of gas, which creates high pressure inside the wellbore and results in the fracturing of the rock sample. It is important to note that for dual-hole rock samples, the ignitors of the two wellbores are series-connected to ensure synchronized deflagration of both wellbores.  
In the test, the axial pressure is kept at 12.5 MPa and other variables such as temperature, the borehole number, and the mass of deflagration agent are set as in Table 1.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample No.** & **Temperature** & \
\begin{tabular}{c} **The Borehole** \\ **Number** \\ \end{tabular} &
\begin{tabular}{c} **The Mass of Deflagration** \\ **Agent in Each Borehole** \\ \end{tabular} \\ \hline H1 & 20 & 1 & – \\ H2 & 80 \({}^{\circ}\)C & 1 & – \\ H3 & 150 \({}^{\circ}\)C & 1 & – \\ H4 & 40 \({}^{\circ}\)C & 2 & – \\ \hline D1 & 20 \({}^{\circ}\)C & 1 & 10 g \\ D2 &