Wellbore stability analysis is perfformed for economically improving of drilling operation. Identification of diverse types of rupture in the well bore is crucial in stability analysis. Due to reservoir pressure drop and reduction of productivity index , hydraulic fracturing is done in order to increase the permeability and production rate of the well. For this purpose, fluid is injected inside the well to induce fractures in the well walls. Hydraulic fracturing has received much recognition as a reliable method for the stimulation of oil reservoir. In this study, conducted on 400 m of limestone in fahlyian reservoir in darkhovein oil field, shear pressure and compressional failure are determined by a series of parameters including rock mechanic and well logging information as well as maximum and minimum in situ stress in vertical and horizontal directions. Safe mud window was defined between 0.84 and 2.4 g/cm3. The minimum allowable mud pressure for preventing the shear failure was between 33.51 and 52.89 MPa and the maximum range was determined between 40.47 and 55.97 MPa. Furthermore, minimal required mud pressure for inducing compressional rupture and hydraulic fracturing was estimated between 108.87 and 151.38 MPa.
)
