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ISRM India Journal- Half Yearly Technical Journal of Indian National Group of ISRM
Year : 2012, Volume : 1, Issue : 1
First page : ( 25) Last page : ( 30)
Print ISSN : 2277-131X. Online ISSN : 2277-1328.

Determination of Stress Orientation and Magnitude in a Directional Well Bore, Case Study: Mansouri-54 Wellbore of Southwest Iranian Oilfield

Saeidi O., Ahmadi M.

Rock Mechanics Department, Tarbiat Modares University, Iran

Online published on 28 May, 2012.

Abstract

Knowledge of insitu stress tensor is critical in developing petroleum fields, mineral resources and other underground excavations. Since this research is focusing on stress determination in a directional wellbore, based on available data, the well-54 from the Mansouri field was selected as a case study. The wellbore is located in the Zagros basin in south-western of the Iran. With ultrasonic borehole image log (UBI), the orientation of the minimum horizontal stress (Sh) was determined using borehole breakout method. Then, the magnitude of vertical stress (Sv) was calculated by integrating density formation from surface to the given depth. In fact, magnitude of Sh was determined by generalizing Breckels and van Eekelen's expressions (Fjaer, et al. 2008). At any given depth the maximum horizontal stress (SH) constrained by Anderson's faulting theory and Coulomb faulting theory for an assumed coefficient of friction. In the present study, the stress gradients have indicated that the stress regime corresponds to the strike slip faulting condition (Sx≡SH>Sz ≡Sv >Sy ≡Sh). It was observed that Sh direction corresponds to the Zagros thrust belt and optimum orientation of drilling the wellbores to minimize wall collapse in this area is located on NE-SW direction.

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Keywords

Insitu stress, Mansouri-54 wellbore, Anderson's faulting theory, Image log, Zagros thrust belt.

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