Wellbore Stability Evaluation for Mishrif Formation


During drilling operations for the E oilfield in the Mishrif formation in southern Iraq, stuck pipe has been identified as a significant geomechanical problem for several wells. In this study, a 1-D mechanical earth model (MEM) of the Mishrif formation is compiled based on its state of stress and rock strength parameters and is utilized to assess the contribution of borehole collapse leading to the stuck pipe problems. The MEM model is based on the principal in situ stresses and their orientation obtained from wireline logs measurements, measuring while drilling (MWD), and leak off test (LOT). Rock strength properties are obtained from empirical equations and extended leak off tests. The in situ stresses are transformed to calculate and analyze mud pressure conditions for all wellbore azimuths and inclinations. Two different failure criteria (the Mohr-Coulomb and Mogi-Coulomb rock failure criteria) are used in order to determine feasible drilling trajectories (with respect to the σH orientation) and mud pressure conditions for several wells. This work was conducted to study the behavior of the collapse pressure for Mishrif formation under a normal faulting (NF) in situ stress regime. The results of this study show that wells characterized by stuck pipe are drilled along azimuths which promote wellbore collapse. Based on the MEM results, the mud pressure window is calculated, and stable azimuths and inclinations for each well are suggested. If a specific azimuth for a well cannot be altered, an optimum inclination is recommended to reduce the severity of the borehole collapse. This study based on a 1-D MEM model for directional drilling can improve the well drilling efficiency by reducing non-productive time due to the wellbore instability.

Meeting Name

SPE Middle East Oil and Gas Show and Conference 2017 (2017: Mar. 6-9, Manama, Bahrain)


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Drilling fluids; Oil field equipment; Borehole stability

International Standard Book Number (ISBN)


Document Type

Article - Conference proceedings

Document Version


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© 2017 Society of Petroleum Engineers (SPE), All rights reserved.

Publication Date

01 Mar 2017

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