Review of underbalanced drilling techniques highlighting the advancement of foamed drilling fluids

Abstract Overbalanced drilling is the most common technique; nevertheless, it has several disadvantages such as formation damage, mud losses, and stuck pipes; challenges that are in high permeability zones highly fractured formations. To overcome those issues, underbalanced method could be implemented. The (UBD) technique widely utilized hard, under pressure, depleted, fractured/vuggy Low-density fluids usually used UBD operations categorized into a gas (i.e., air, nitrogen, natural gas) or two-phase mist foam). Although foamed fluid attracted attention enhanced oil recovery hydraulic fracturing operations, ideal for due to its low density efficient transport capacity. This paper highlights applications, limitations, advantages, of operations. It also discusses foam chemistry, structure, characterization, rheological properties. Finally, this few successful utilizing worldwide.