# Research on Nanoparticle-Enhanced Cooling Technology for Oil-Based Drilling Fluids
## 3 Results and Discussion
### Rheology of Nanoparticle-Enhanced OBDFs  
Rheological property is one of the key indexes of drilling fluids, which directly affects their ability to carry chips in downhole operations, the effect of maintaining wellbore stability, and determines the adaptability and stability of drilling fluids in extreme environments. The impact of different nanoparticles on the rheological properties of OBDFs is illustrated in Figures 3-5. However, the changes before and after hot rolling were relatively small, indicating that the OBDFs have good stability. The introduction of nanoparticles enhanced the rheological properties of OBDFs under HTHP conditions, thus improving their stability and adaptability in complex downhole environments.  
as higher plastic viscosity can effectively improve the load-carrying capacity and wellbore stability of drilling fluids.  
YP is an important indicator of the shear resistance of drilling fluids, which is crucial for wellbore stability and the safety of drilling operations. The YP of OBDFs with nanoparticles almost did not change before and after hot rolling, as shown in Figure 5. When CNTs, SiO\({}_{2}\), and Al\({}_{2}\)O\({}_{3}\) were added at 3%, the YP of drilling fluids increased to 9.5 Pa, 8 Pa, and 10 Pa, respectively. These results indicate that these nanoparticles are able to effectively improve the shear resistance of drilling fluids under high temperatures after hot rolling, thus maintaining the stable fluidity of the drilling fluids under complex downhole conditions.  
Overall, CNTs showed excellent results in enhancing the rheological properties of OBDFs, especially in the most significant improvement of AV and PV after hot rolling. The unique structure of CNTs could form a network in the fluids, effectively dispersing the stress and maintaining the fluidity and stability of the drilling fluids under HTTP environments. In contrast, although Al\({}_{2}\)O\({}_{3}\) is not as effective as CNTs in improving viscosity, it has outstanding performance in improving the shear resistance of drilling fluids, especially in the improvement of dynamic shear force after hot rolling. This indicates that under the complex downhole conditions of HTTP, the OBDFs with nanoparticles added can effectively maintain the rheological properties and provide a more reliable technical guarantee for deep drilling operations.  
The breaking voltage reflects the stability of emulsion in OBDFs, which directly affects the performance and effectiveness of drilling fluids in drilling operations. The effects of different concentrations (0% to 3%) of nanoparticles (CNTs, SiO\({}_{2}\), and Al\({}_{2}\)O\({}_{3}\)) on the emulsion-breaking voltage of OBDFs are shown in Figure 6. OBDFs without added nanoparticles had the highest breaking voltage of 936 V, showing good emulsification stability. With the increase in nanoparticle concentration, the emulsion breaking voltage decreased significantly, and the emulsion stability gradually decreased. Among them, CNTs showed the smallest decrease, Al\({}_{2}\)O\({}_{3}\) was the second largest, while SiO\({}_{2}\) showed the largest decrease. When the nanoparticle concentration was increased to 3%, CNTs, Al\({}_{2}\)O\({}_{3}\), and SiO\({}_{2}\) decreased the emulsion breaking voltage of OBDFs from 932 V to 891 V, 814 V, and 772 V, with decreases of 4.40%, 12.66%, and 17.17%, respectively. Although the emulsion breaking voltage decreased with the increase in nanoparticle concentration, it always remained above 700 V, indicating that the drilling fluid still had good stability.  
Figure 6: Emulsion-breaking voltage of drilling fluids hot rolling after addition of nanoparticles.