In this study, different types of drilling fluids are developed and analyzed for a mature oil field. The optimum conditions were developed for shallow and deep formations. The experimental procedure that was followed for viscosity, fluid loss, density, and pH calculations is based on the standards dictated by API RP 13B. At the end of the experiments, it was also observed that for shallow depths, 0.2-0.3 lb of caustic soda will be enough for one barrel of drilling fluid. On the other hand, lignosulphanate type of drilling fluid should have 20 lb bentonite, 1-2 lb KSSB, 2-3 lb FHLS, 3-5 lb CMC, and 0.3-0.4 lb caustic soda for one barrel of drilling fluid.