Investigating the effect of carbon nanotubes and shale on the rheological properties of water-based drilling fluid

This study investigated the effect of powdered Shale and carbon nanotubes (FMWCNT) with polar functional groups OH and COOH on the rheological properties of lightweight drilling fluid weighing 63 pcf. In the first step, a fluid was used as a base, and six fluids containing nanotubes (three samples with OH functional groups and three samples with COOH functional groups) were prepared at ambient BHR (77 °F) and mud circulation at simulated bottom hole temperature (250 °F) at concentrations of 0.01, 0.05, and 0.1% (w/w). After that, the rheological properties and filtration values (FL) were measured. The results show that the highest effect was observed at the concentration of 0.05% for the COOH functional group, which increased the rheological properties in both BHR and AHR conditions and decreased the FL values. In addition, the based mud was significantly improved by formulating it with 20 g of powdered Shale and 0.05% nanotubes with COOH functional groups. Compared to the based mud, the apparent viscosity and filtration values (AHR condition) were 37.5% and 67.8% improved, respectively.