## 3 Results
### Physics-Based Simulation Results  
#### 3.1.1 Result 1  
The first computer swab and surge experiments were conducted using the drilling fluids shown in Figure 3. The simulations were performed at different tripping speeds while circulating. Figure 8a,b show the critical allowable swab and surge tripping speeds that led to the lower limit (i.e., at 1.93 sg) and the upper limit at the casing shoe (i.e., 2.06 sg), respectively. The presented examples were obtained from the results in deviated wells filled with 2.0 sg 80:20 and 90:10 OBMs. The comparison shows that the model prediction varied in the different fluid types. For instance, in the well filled with 80:20 OBM, the swabing pressures obtained from Robertson, Stiff, and Bingham plastic were almost equal; however, the power law model underpredicted the results. For the 90:10 OBM, the power law and the Robertson swab speed predictions were closer, but the Bingham plastic deviated from the two models. On the other hand, surge speeds show different behaviors. Another observation is that the 80:20 OBM surging pressure decreased as the flow rate increased. In contrast, the three models in the 90:10 OBM showed an increase in surging pressure when the flow rate increased up to 300 lpm and then decreased as the flow rate increased. The simulation results reveal that one cannot conclude which hydraulic model to trust when designing the swab and surge model unless they are compared with measurement. The simulation results also showed that the swabing speed was higher during circulation, and the surging speed was higher when there was no circulation. To reduce the tripping time, it was important to trip out while in circulation and trip in while de-activating the rig pump. For further model performance evaluation, the swabing speed was selected when the circulation flow rate was 600 L per minute (lpm), and the surging speed was selected without the flow rate. The results are presented in Figures 9-12. The results  
Figure 7: Tripping out dataset.  
show the swabing speed in the deviated and vertical wells filled with the two different drilling fluids.  
Figure 8: (**a**) Example of swabing and surging effects in the 2.0 sg 80:20 OBM filled in a deviated-well. (**b**) Example of swabing and surging effects in the 2.0 sg 90:10 OBM filled in a deviated well.  
Figure 9: Swabbing comparisons of 2.0 sg 80:20 and 90:10 OBMs filled in deviated and vertical wells.  
The percentile deviations of the BP from the PL and RS model predictions were calculated for better quantification. The comparisons are presented in Tables 5 and 6. As shown in Table 5, in vertical and deviated wells filled with the 2.0 sg 80:20 OBM drilling fluid, the BP swabbing speed model predictions were approximately 13.1% and 12.4% higher than the PL model, respectively. On the other hand, for the 2.0 sg 90:10 OBM in the inclined and vertical wells, the BP model predictions were approximately 5.1% and 4.8% higher than the RS, respectively. In the inclined well filled with 2 sg 90:10 and 80:20 OBMs, the surging speed model predictions deviated from the PL by 17.6% and 25.9%,  
Figure 11: Swabbing comparisons of 1.96 sg 80:20 and 90:10 OBMs filled in deviated and inclined wells.  
Figure 10: Surging comparisons of 2.0 sg 80:20 and 90:10 OBMs filled in deviated and vertical wells.  
respectively. Table 6 shows the results obtained from the 1.96 sg drilling fluids. As shown, for both fluid types and wells, the BP deviation from the PL and RS recorded lower values.