Study Of Nanosize Carbon Spheres As High Temperature Drilling Fluid Lubricant

The rotating resistance and lifting resistance of drilling string would increasemarkedly in drilling of deep or ultra-deep wells, and horizontal wells, cluster wellsand highly deviated wells. The demand on lubricating property of drilling fluid wasincreased highly in drilling works, that’s because the lubricating property of drillingfluid is the main adjustable factor of the rotating or lifting resistance and the toolwears. The lubricating property, influencing the drilling work greatly, play a vital rolein reducing sticking or other down-hole troublesome condition, reducing tool wearing,ensuring the safety and so on. The lubricating property of drilling fluid consists of thedrilling fluid self-lubricity and the mud cake lubricity. Now, there are two methods toimprove the mud lubricating properties, one is adding some lubricants reasonably intothe drilling fluid to reduce the mud friction coefficient and the other is improving themud cake quality to increase the lubricating properties of the mud cake.The nanomaterials has various excellent characteristics and properties, whichhas very broad application prospects in many areas. As a popular research innanomaterials field, carbon nanomaterials not only has the volume effect, surfaceeffect, quantum size effect, macroscopic quantum tunneling effect and mechanicalproperties of nanomaterials, but also has its unique advantages, such as thermalstability, high strength and so on. The carbon nanomaterials had a wide range ofapplications due to its excellent performance.With the performance of hightemperature resistance and high strength, the spherical carbon materials could beintroduced into the drilling fluid. The spherical carbon material could play the role oflubrication, due to its small size and high strength, except its spherical smoothsurface. The nanometer carbon spheres could not be easily cleaned or be slappedbroken in the drilling fluid system. In general, it is feasible that the nanometer carbonspheres used as a drilling fluid lubricant.Two kinds of nanosize carbon spheres were synthesized in this study, one was Resorcinol-Formaldehyde polymer nanosize colloidal carbon spheres and the otherwas nanosize carbon spheres based on glucose. The scanning electron microscopy,Fourier transform infrared spectroscopy, and thermal gravimetric analysis showedthat both the nanosizer carbon balls had a spherical morphology and smooth surfacewhich can play a lubrication action in the drilling fluid. The former carbon sphereshad uniform particle size distributing around500nm, with poor dispersity in waterwhich could maintain its quality stably at400°C. And the latter carbon spheres had aparticle size distributing between700nm-900nm and had a good hydrophilicity whichmade it could be dispersed well in the water and drilling fluid, moreover, it couldmaintain its quality stably at400°C. These two carbon spheres could meet therequirements of the temperature resistance ability of the high temperature drillingfluid lubricant.The experiments showed that both of these two nanosize carbon balls couldimprove the lubricating properties of the drilling fluid and be used as a drilling fluidlubricant. With0.4%percent of Resorcinol-Formaldehyde polymer nanometer carbonspheres, the lubricating properties of drilling fluid enhanced significantly; the drillingfluid lubrication coefficient reduced by22.8%and the mud cake sticking coefficientreduced by20.1%after the drilling fluid aged treatment at high temperature (180℃,16h). But the rheological property of drilling fluids was also affected as the viscosityand shear increased after the drilling fluid aged. However, the nano size carbonspheres glucose-based had a good shear thinning effect, the drilling fluid viscosit yand shear had declined regardless of high-temperature aging. The effect on thelubricating properties was best with0.5%percent of nano size carbon spheresglucose-based, after ageing treatment at180℃for16h, the drilling fluid lubricationcoefficient could be reduced by25.2%but the mud cake sticking coefficient hadincreased by6.9%. Moreover, both of these nanosize carbon spheres could reduce thefilter loss of drilling fluid.