*4.4. Sensitivity of the Measured Anisotropic Relative Permeability Data on the Simulation Model*

We tested the relative permeability in three directions, and we call the relative permeability curve in the x direction obtained by the experiment No. 1, the relative permeability curve in the y direction No. 2, and the relative permeability curve in the z direction No. 3. No. 1 and No. 2 relative permeability (the smallest difference), No. 1 and No. 3 relative permeability (the biggest difference), and No. 2 and No. 3 relative permeability (large difference) are applied in the homogeneous model x, y, and z direction, respectively (for the convenience of the description later, we named these three cases low difference, high difference, mid difference). Then, we studied the effect of the difference in anisotropic on the results of the numerical simulation.

The water cut of low difference shows the injected water breakthrough first (waterless oil recovery period is the shortest) with a breakthrough time of 6.3 × <sup>10</sup><sup>4</sup> days, the water cut rises fastest, the final water cut is the highest, and the daily oil production drops the earliest. The breakthrough time of high difference is later than that of low difference, which is 6.9 × 104 days. The final water cut of high difference case is the lowest. The breakthrough time of mid difference is the latest, which is 7.5 × 104 days. After the breakthrough, the water cut rises rapidly, and at 8.8 × 104 days, the water cut exceeds that of high difference, and the water cut is 68.24%. Accordingly, the daily oil production of high difference decreased earlier than that of mid difference, but the daily oil production of high difference exceeded both at 8.8 × <sup>10</sup><sup>4</sup> days (Figure 7).

**Figure 7.** Water cut and daily oil production of different anisotropic relative permeability.

According to the characteristics of the relative permeability curve, the difference of the relative permeability curve between low difference x and y is the smallest, and the difference of residual oil saturation is only 5%. Therefore, the injected water advances uniformly in the x and y direction and breaks through fastest. The difference between the relative permeability curve of high difference x and y is the biggest, and the difference in residual oil saturation is 26%. The displacement efficiency of injected water in the y direction is higher, so the path of injected water to the production well shifts in the y direction, and the path becomes farther, so the breakthrough time is later than low difference. The relative permeability curves of mid difference x and y are quite different, and the difference of residual oil saturation is 21%, but the displacement efficiency in both directions is high, so the injected water breakthrough is the latest. It is precisely because of the high displacement efficiency of mid difference in both directions, once the injected water breaks through, the remaining oil is the least, and the water cut increases rapidly. After the injected water of high difference breakthrough, there is more remaining oil in the x direction, with the continuous increase in injected pv, this part of the remaining oil is gradually drained, resulting in a smaller increase in water cut than the other two cases.
