Investigating the effect of carbon nanotubes containing carboxyl and hydroxyl functional groups on the rheological properties of water-based drilling fluid

Nowadays, with the advancement of nano technology, several researches have been done on using Nano additives to solve the existing problems of the oil industry. One of the main challenges of drilling is thermal degradation of polymer additives in well drilling, which will lead to a decrease in rheological properties, increase in filtration values. Entering large amounts of filtrate into the shale formation will increase pore pressure, shale instability, cause many problems. Solving this problem by using high temperature polymers or carbon materials with high thermal conductivity can prevent thermal degradation of polymers and also block the nanometer pores of shale. In this research, we decided to investigate the effect of carbon nanotubes (FMWCNT) with two polar functional groups, OH and COOH, on rheological properties of light weight water base drilling fluid with a weight of 63 pcf.
In this study, a base fluid sample and 6 fluid samples containing nanotubes (3 samples with OH agent and 3 samples with COOH agent) with concentrations (w/w) of 0.01, and 0.05 and 0.1% were made and under the conditions of laboratory environment temperature. (BHR:77 °F) and mud circulation at the simulated bottom hole temperature (AHR:250 °F) Rheological properties and then filtration values (FL) have also been measured. The results have shown that among the concentrations used, the best effect on the rheological properties was observed at a concentration of 0.05% for the COOH functional group, which increased all rheological properties in both BHR and AHR conditions and also decreased the FL values.