Abstract
Oil and gas have been facing various difficulties in well drilling due to shale hydration and swelling when in physical contact with water. Oil-based muds (0BMs) and synthetic based muds (SBMs) have been shown to have superb effort to address the drilling problems of wellbore instability due to the shale hydration. Nevertheless, OBMs and SBMs compositions are threatened agent to the environment which makes water-based muds (WBMs) as viable alternatives. WBMs usually require shale inhibitors, otherwise, water in the fluid may diffuse into the shale formation to cause a fracture, swelling/hydration and delamination of shale. Conventional inhibitor such as KCl is known for its good shale activity but not ecofriendly. Other compounds including amines, imines, and their polymers; gelatin, ionic liquids, the natural compound as well as graphene and graphene composites that have been tested by various authors either have HTHP or the environmental limitation or fail in their application in plugging pore throats in shale. Nanomaterials with a wide range of nanosizes have been detected to greatly hinder shale swelling due to their ability to plug micro-openings in shale by forming compact filter cake to minimize fluid loss and prevent downhole pressure transmission. This review paper is structured to give an overview of shale inhibitors, show the defaults in the convention inhibitor and the viability of nanoparticles as efficient, cheap and sustainable inhibitors. (C) 2019 The Authors. Published by Elsevier Ltd.