Development of a Geomechanics Program for Wellbore Stability Analysis

Development of a Geomechanics Program for Wellbore Stability Analysis

Saeidi, Omid (Iranian Offshore Oil Company, Tehran)
Rahimi Dalkhani, A. (TU Delft Applied Geophysics and Petrophysics)

2023

A geomechanics program for wellbore stability analysis has been developed consisting of two modules: an analytical-based solution and a numerical-based solution. In the first part, input data are imported, including petrophysical well logs, pressure data, formation well tops, and a well path. Lithology intervals are set with proper prediction equations to calculate rock mechanical properties based on laboratory tests. In-situ stress and pore pressure are determined using different methods, including the poroelastic plane strain model and stress polygon. From the theory of plane strain, new equations are solved to determine horizontal tectonic strains (ϵ h, ϵ H) from drilling events such as total mud loss and breakout during drilling. Safe mud weight bounds are calculated through depth and in different azimuths and inclinations applying the Mohr-Coulomb and the Mogi-Coulomb failure criteria. The latter underestimated the minimum mud weight to prevent wellbore breakout. The transversely vertical isotropy of shale formation is programmed with multiple stress transformations via the weak-plane method. In the second module, a 3D model around the wellbore is discretized with hexahedral eight-point elements and programmed using the finite-element (FE) method. Rock mechanical property and displacement boundary conditions are applied to solve FE equations. Stress from the numerical model matched to the Kirsch model and results show that maximum stress concentration around the wellbore corresponds to the wellbore breakout, which has analytically been established. A new well plan across the 3D model was examined to obtain the safe mud weight bounds and results were in agreement with the analytical calculations.

Boundary condition
Failure criterion
Finite-element analysis
In-situ stress
Mechanical property
Mud weight
Transversely isotropy

http://resolver.tudelft.nl/uuid:b47c83de-b8f0-4a48-b3c8-6f9ac9499660

https://doi.org/10.1061/IJGNAI.GMENG-8733

2023-11-22

1532-3641

International Journal of Geomechanics, 23 (8)

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

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© 2023 Omid Saeidi, A. Rahimi Dalkhani