Oxide and Diamond Nanoparticles Modified Drilling Fluid for Deep, Complicated Drilling Conditions

In the context of well drilling and during the process of drilling down and tripping out of drill string, it is the inevitable contact and friction between drill pipe and casing that causes the wear of the drill pipe and casing tube, especially in the case of drilling deep, ultra-deep, and horizontal wells. Compared with steel drill pipe, the wear of aluminum alloy drill pipe appears to be more serious. Nanoparticles as additives in drilling fluids could potentially reduce mechanical friction, greatly enhancing the lubricating properties of drilling fluids and subsequently reducing the drill pipe and casing materials surface losses. Within this study an attempt has been made to improve the lubricating properties of drilling fluid with regard to deep, complicated drilling conditions by adding oxide nanoparticles to the fluid. Spherical alumina (Al2O3), titania (TiO2), silica (SiO8) and diamond nanoparticles were selected as drilling fluid additives. Effects of different types and concentrations of oxide nanoparticle additives on lubricating properties and friction reduction of drilling fluid have been studied by using an extreme pressure lubrication device and a pin-on-disk tester. In pin-on-disk tests, the pin material was AISI316 steel (casing material) and the disk material was 7075 aluminum alloy (drill pipe material). The pin-on-disk friction and wear tests were carried out under the condition that the pin and disk were immerged in drilling fluid. Results indicated that the lubricating properties of water-based drilling fluid significantly improved upon adding an appropriate amount of SiO2 nanoparticles, meanwhile TiO2, Al2O3 and diamond nanoparticles had limited effects on the lubricating properties of drilling fluid. The LR (lubricating factor reduce rate) of drilling fluid increased to the maximum value of 16.6% at 0.5 wt% SiO2 nanoparticles addition. The WV (wear volume) of aluminum alloy disc decreased to the minimum value of 0.31 mm(3) at 0.4 wt% SiO2 nanoparticles addition. On the basis of the above experimental results, 0.4 wt% SiO2 nanoparticles were added to the oil based drilling fluids used in SK-II well drilling, which is a scientific continental drilling project in the Cretaceous Songliao Basin of northeast China. Results showed that the lubricating coefficient of the drilling fluid was reduced by 20.3%, the friction factor reduction rate was increased by 29.7%, and the aluminum disc wear volume decreased by 26.3%.