Investigating the application of carbon nanotubes and shale on the rheological properties of drilling fluid

Nowadays, the challenges of drilling deep wells are reducing the rheological properties of drilling fluids with HPHT and destroying the structure of viscosifier polymer additives which will lead to decrease viscosity, drilling fluid properties and increase filtration values.
This study investigated the rheological properties of lightweight drilling fluid weighing 63 pcf using powdered shale and carbon nanotubes (FMWCNT) with groups OH and COOH. First, one base fluid and six fluids containing nanotubes (3 OH functional samples, 3 COOH functional samples) with concentrations (w/w) of 0.01, 0.05, and 0.1% were made at ambient temperature BHR: (77 oF) and mud circulation at the simulated bottom hole temperature (250 oF). 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 group, which increased the rheological properties in both BHR, AHR conditions and decreased the FL values. Further, by formulating the base mud with 20 gr of powdered shale and the optimal concentration of 0.05% of nanotubes with the COOH group and AHR conditions, the results were significantly improved in such a way that the apparent viscosity and filtration values improved by 37.5% and 67.8% compared to the base mud respectively.
Nanotubes, by intertwining their strings in the drilling fluid, increase the viscosity and improve the ability of the drilling fluid to retain the drilling cuttings. By adding the powder obtained from shale cuttings, these properties have been significantly improved, and a significant filtration control has been established.