**3. Mud properties modification**

Two key parameters of drilling mud are generally investigated, including rheological and mud filtration. Mud rheological properties include plastic viscosity (PV), apparent viscosity (AV), gel strength (GS), yield point (YP), and yield stress (YS), while filtration properties consist of fluid loss volume, filter cake thickness, porosity, and permeability. Both the properties are dependent on the proper mud composition. The clay and polymeric materials generally enhance mud rheology, while the fluid loss additives such as starch and other nano-based materials reduce the fluid loss and cake thickness. Starch is a commonly used additive for improving both the rheological and filtration characteristics of mud.

Shale inhibition is another primary factor that requires attention during the mud design. Wellbore instability due to shale swelling and fluid loss of drilling mud is the main challenge the oil and gas industry faces. Shale is generally a water-sensitive material and causes swelling resulting in other drilling issues. Different additives, including salts and other amine-based materials, have been tested to improve shale stability. Several studies have been conducted to modify mud properties. For instance, a water-based mud was developed using an appropriate amine derivative, poly-ethoxylated alkyl diamine as a potential shale inhibitor agent instead of other conventional alternatives. The developed mud has optimally improved the performance of previously formulated HPWBMs [4].

Shale inhibition of amine derivative was examined using a new procedure, namely WSP, which showed better performance in bentonite-based mud systems. The system was found appropriate and an excellent alternative to OBM and SBM when tested in the South China Sea deepwater well. The mud displayed better performance by excellent shale stability, clay inhibition, lubricity, and high rate of penetration (ROP). The mud showed lower cost due to no issue caused during the drilling operation [5].
