β-Cyclodextrin modified TiO2 nanofluids to improve the stability and thermal conductivity of oil-based drilling fluids

As we all know, the application of oil-based drilling fluids (OBDF) in shale oil and gas horizontal wells and complex deep wells has become more and more extensive in recent years. However, under high temperature and high pressure (HTHP) conditions, the failure of drilling equipment and the decomposition of emulsifiers and additives seriously affect the normal completion of drilling operations, so it is worthwhile to study a high-efficiency additive to improve its performance. In this experiment, functionalized TiO2 nanoparticles (beta-CD/TiO2) firstly were prepared, and then used different analytical methods to characterize the nanoparticles. Meanwhile, the effects of different nanofluids on the novel OBDF (nano-OBDF) were measured using a Turbiscan stability analyzer. The results show that 0.4% beta-CD-TiO2 nanofluids could maximize the stability of nano-OBDF. Furthermore, the thermal conductivity of nano-OBDF at different temperatures and concentrations was investigated with the thermal conductivity analyzer KD2 Pro. The results manifest that the thermal conductivity of nano-OBDF increases accordingly when the volume fraction of nanoparticles increases from 0.2% to 1%. At the same time, when the temperature ranges from 25 degrees C to 50 degrees C, compared with the base fluid, the thermal conductivity of nano-OBDF also shows an upward trend. All these results indicate that the research has great potential to improve OBDF stability and transfer thermal loads generated by friction between the reservoir wall and the drill bit. Finally, by comparing the typical theoretical model with the experimental data, an empirical model that applies to this experiment is obtained.