The shale instability is a great challenge for both conventional and unconventional hydrocarbon exploitation. Although numerous chemical inhibitor additives have been used to reduce shale swelling, the efficacy of each additive may vary in field conditions due to the heterogeneous nature of the shales, in terms of mineralogy, chemistry, microstructure, etc. Therefore, a special study for in-field inhibitor implementation is essential. The traditional additives including potassium chloride, polyamine, partially hydrolyzed polyacrylamide, and formulated novel chemical swelling inhibitors were used to carry out extensive laboratory investigations on shale inhibition. The formulated polyamine and xantham gum-based inhibiors acted as the most effective inhibitor to control the swelling up to 40%. The X-ray diffraction studies reveal the shale types, microstructures, chemistry, and their control on inhibition behavior. The montmorillonite-rich shales are significantly hydratable and expansive, while organic matter shows a negative correlation with shale swelling.