## Appendix A Combustion Tube Test Details  
A combustion tube experiment was performed in order to assess the potential of the HPAI method for rocks of the Bazhenov Formation [36; 37; 56]. The combustion tube consisted of 14 sections, equipped with individual external heaters, continuous temperature control on the section wall, and in the central part. The temperature control was carried out using built-in thermocouples. To reduce the outflow of heat into the environment, each sector on top of the heater was covered with thermal insulation. The parameters obtained in the experiment (combustion front's speed, maximum reaction temperatures, and composition of the gases) were used in the numerical simulation of the HPAI process. We used a bulk model consisting of rock samples from target oil fields as a porous media in the tube. The reservoir temperature was equal to 100 \({}^{\circ}\)C, and the reservoir pressure was 27 MPa. The bulk model was saturated with a probe of degassed oil. The combustion tube was filled with crushed rock with a fraction of 0.1-1 mm and consolidated samples of various shapes. The first two sections were filled with sand and rock samples of the Bazhenov Formation, the next four--only with the Bazhenov Formation's rock samples, the remaining eight--with sand. The layout of the samples is shown in Figure 11.  
The prepared bulk model of the combustion tube was pressurized with dry air, and then the model's gas permeability (to air) at ambient temperature (22 \({}^{\circ}\)C) was measured. It was equal to 2.8 \(\upmu\)m\({}^{2}\). Then, 5 L of oil was injected through the tube from bottom to top. The combustion tube's pore volume and the initial oil saturation were determined based on volumes of injected and released oil. The pore volume and porosity were 2138.4 cm\({}^{3}\) and 29.8%, respectively, and the initial oil saturation was 100%. In addition, the bulk model's initial permeability for oil at ambient temperature (22 \({}^{\circ}\)C) was determined (3.3 \(\upmu\)m\({}^{2}\)). Based on the results of the high-pressure differential scanning calorimetry (DSC) performed at a pressure of 8 MPa and a heating rate of 1 \({}^{\circ}\)C/min, it was decided to heat the first two sections to a temperature of 200 \({}^{\circ}\)C to accelerate the initiation of combustion. In all other sections, a reservoir temperature of 100 \({}^{\circ}\)C was maintained. The experiment was carried out in the following order. 1. Nitrogen was injected through the vertical combustion tube at a pressure of 8 MPa with a volumetric flow rate of 2.4 L/min, while the tube was heated by zones until it reached the specified temperature regime. 2. After the combustion tube reached the specified temperature regime, the air injection began with a volumetric flow rate of 2.4 L/min. 3. With a predetermined frequency, samples of the displaced fluid and gas samples were probed at the outlet of the combustion tube in order to determine the content of carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and hydrocarbon gases. According to the temperature logs, the propagation of the combustion front along the tube was recorded. 4. At the final stage of the experiment, the external heating was turned off in order to stop the generation of hydrogen sulfide inside the tube. 5. Rock samples were extracted from each section of the tube for further research. The air supply was stopped when the oil combustion front reached Section 5. Thus, the samples in CT section were not exposed to high temperatures. At each stage of the experiment, the gas and oil sample composition was analyzed to assess the intensity of the oxidation reactions. Rock-Eval pyrolysis of the crushed core before and after the chemical and thermal exposure was conducted. The total residual oil saturation in the core pack was 2%. Minimal residual oil saturation was observed in zones that the combustion front has passed through, whereas the maximum oil saturation corresponds to the areas in front of the combustion front.