Implementing the drilling fluids in drilling operations is of paramount importance owing to the variety of applications and benefits they provide. Materials added to drilling fluid could cause numerous environmental problems in soil and water resources, and these problems are more pronounced in offshore as compared to land fields. Heavy metals such as mercury, barium, arsenic, lead, and nickel exist in drilling fluid, which bring detrimental damages to the environment. Moreover, heavy metals exist in oil-based muds due to presence of oil where their nickel and vanadium are much greater than other heavy metals. Additive materials and heavy metals existing in drilling fluid could pose irreparable environmental damage if fluid loss into the formation occurs. Regarding to the fact that drilling fluid loss occurs via the open fractures in the wellbore, the main aim of this study is to evaluation of wellbore fractures via implementing the FMI log and fracturing pressure using the slowness of compressional and shear waves. A total of 61 fractures in Dalan formation and 72 fractures in Kangan formation are interpreted and fracturing pressure for these formations, ranges between 8400 and 9450 psi. Implementing the results obtained from this study, drilling fluid loss into the formation and subsequent environmental damage could be prohibited via controlling the pumping pressure and density variation of drilling fluid in accordance with the formation fracturing pressure.