(3) Construction model

The anti-nine-point well network with the size of 220 × 210 m was adopted in this study and the development method was in-situ combustion. The Du 66 block was inclined from the northwest to the southeast, and the dip angle of the stratum was generally 5◦~10◦, which can truly reflect the changing trend of the stratum. The injection well was located in the center of the block, and the production wells were distributed at the corners of the block. The 3-dimensional distribution of the original oil saturation and porosity has been shown in Figure 1. From the oil saturation model of the Du 66 block (Figure 1a), the oil saturation was evenly distributed, and the initial oil saturation was 0.69 in average. From the porosity model of the Du 66 block (Figure 1b), there were 25 layers in the stratum. The porosity of the odd layers was 0.21, and the porosity of the even layers was 0.0013. The porosity was evenly distributed in the transverse direction.

**Figure 1.** Three-dimensional distribution of the initial oil saturation and porosity. (**a**) Initial oil saturation distribution; (**b**) porosity distribution.
