Shales make up about three fourths of drilled formation and over 90% of the wellbore instability problems that occur in shales.it still a serious problem in not only the petroleum industry but also in the mining and construction industries. Before any measures are taken to address this problem, it is crucial that potentially problematic formations and the mechanisms of wellbore instability be identified. Once the mechanisms are understood, well planning, drilling fluid design, and drilling operation strategies can be implemented to ensure wellbore stability. Due to the unique mechanical and physicochemical properties of shales, it is well- recognized that wellbore instability in shales is a complicated problem.
Shale cuttings consisting of different montomorillonite content were collected from four different wells in Sinai. They were evaluated using X-ray diffraction (XRD), X-ray fluorescence (XRF) and cation exchange capacity (CEC) using Methylene Blue (MB), hence classified into shale 1, 2 ,3 and 4. Swelling index of the shale measured using compressed disks of shale in contact with OCMA bentonite for 20 hrs using the Linear Swell Meter (LSM). Nanoparticles in terms of CuO, Graphene nano platelets and SiO2 used as an inhibitor of swelling of shale cuttings. The inhibitors are added to OCMA bentonite as well.

The inhibition of swelling of these shale cuttings using KCl achieved a decrease in swelling that ranged from 15 % at 7 % (shale 1), 14 % at 6 % (shale 2) ,14% at 4% (shale 3) and 17% at 9 % (shale 4)