Drilling fluids play great importance to the success of MPD (Managed Pressure Drilling) and MCD (Mud Cap Drilling) operations. On MPD projects, the correct design of the drilling fluids properties, such as, density, rheology, anchor point position and compatibility should be precisely adjusted in order to operate in good and safe performance, especially in a statically underbalance MPD projects. Exceptional importance should be addressed to the initial mud density to provide useful capacity to carry out a Dynamic Porous Pressure Test (DPPT). MCD operations require a suitable drilling fluid project due gas migrations, costs and cuttings transportation issues, related to LAM (light annular mud) and sacrificial (SAC) fluids. The objective of this paper is to present the lessons learned in drilling fluid projects during MPD and MCD operations in Brazil's offshore wells. The study will focus on desired properties, simulations, adjusted hydraulics models, formulations and involved costs, considering water and olefin based drilling fluids.