Highly efficient modified activated carbon as shale inhibitor for water based drilling mud modification

Maintaining wellbore stability while drilling is critical to mitigate operational problems and reduce well construction costs. This is clearly evident in the case of drilling troublesome intervals such as shale formations. The current study describes the effect of diethylenetriamine modified activated carbon (DETA-AC) on the swelling inhibition of shale samples with high clay content and rheological features of water-based muds (WBM). DETA-AC provides a huge surface area, a prominent number of functional groups, and a relatively non-toxic nature that makes it suitable for environment-friendly additives to drilling fluids. In the current study, the DETA-AC was utilized as an environment-friendly swelling inhibitor. Rheology tests were conducted by hot rolling the WBM at 212°F temperature and 500 Psi pressure for 16 hours. The inhibition features were assessed by dispersion recovery test, shale inhibition stability test, and linear swelling test. The outcomes revealed that DETA-AC modified WBM (DETA-AC-WBM) showed high shale recovery (93.3 %) in dispersion test as related to unmodified WBM (73.6 %), the aqueous solution of KCl (51.5 %), and commercial shale inhibitor mud (74.9%). shale cuttings treated with DETA-AC-WBM displayed stable behavior and resistance against water for up to 2 days. Bentonite in DETA-AC-WBM demonstrated a prominent decrease in linear swelling 58 % as compared to bentonite in water. While the rheological characteristics of DETA-AC-WBM remain almost the same after hot rolling. To confirm the adsorption of DETA-AC on the surface of the clay, its inhibition mechanism was explored by several characterization techniques such as Fourier transforms infrared spectroscopy (FT-IR) analysis, thermogravimetric analysis, scanning electron microscopy, and energy dispersive X-Ray spectroscopy. The proposed inhibition mechanism suggests that DETA-AC carries functional groups that can disturb the hydrogen bonding among H₂O and shale material. Subsequently, the clay surface is protected against the adverse effects of clay-water interactions.