Analysis of vertical, horizontal and deviated wellbores stability by analytical and numerical methods

Wellbore stability problems are known to cost the oil and gas industry billions of dollars each year. However, these costs can be significantly reduced through the application of comprehensive geomechanical models. This paper is relevant and is appropriate in the oil and gas industry. The objective of this paper is the comparison of four rock failure criteria, named the Mohr–Coulomb, Mogi–Coulomb, Modified Lade and Tresca yield criterion and to apply them to determine the optimum drilling direction and mud pressure. The stability models has been applied to a well located in Iran oil field and leads to easily computed expression for the critical mud pressure required to maintain wellbore stability. Then the finite difference method was used to show the validation and accuracy of predicted mud pressure and investigate the wellbore stability in different states of vertical, horizontal and deviated. The results showed that the Mohr–Coulomb and Tresca criteria estimate the highest minimum mud pressure required for wellbore stability while the Mogi–Coulomb and the Modified Lade criteria estimate the lowest minimum mud pressure. Nevertheless, the mud pressures predicted by all these four criteria are acceptable and can be used.