Stress field analysis and its effect on wellbore stability and selection of optimal wellbore trajectory in the Asmari Formation of Ahvaz oil field


1 Department of petroleum engineering, Ahvaz faculty of petroleum, Petroleum University of Technology, Ahvaz, Iran

2 Department of Petroleum Engineering, Omidiyeh Branch, Islamic Azad University, Omidiyeh, Iran


The problem of instability of wellbore is one of the common and dangerous problems during drilling operations of oil and gas wells, which causes heavy financial loss to drilling industry every year. Today, companies related to drilling industry use rock mechanic science as a tool for reducing such of problems. In this study, by using the science of rock mechanic and related data of one of wells drilled in the Asmari reservoir of Ahwaz oil field, the stability condition of the wellbore was investigated. Then, the reason for occurrence of the instabilities in this well, and also a solution for drilling the future well in much more stable way were studied. To achieve this goals, the data of four depths from this well which had stability problems were used to perform sensitivity analysis using Mohr-Coulomb and tensile failure criteria. Also, due to the complexity of sensitivity calculations, MATLAB software was used in this article to perform the relevant calculations. The results showed that vertical drilling as well as low mud weight are the main causes of instabilities in this well. According to these analyses, the optimum wellbore trajectory in this field achieved by directional drilling in the direction of the minimum horizontal stress and with inclinations of 27 to 33 degrees. Also, it was deduced that the safe mud weight window of this reservoirs is between 13.13 to 16.16 pounds per gallon. Also, at the end of this study, all possible failure types in different inclinations and azimuths were evaluated and some of them were reported.


Main Subjects

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