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Junction zone stability in coaxial wells of different diameters (on the example of the Khanty-Mansi Autonomous District oil field)

A.V. Seryakov, M.Yu. Podberezhny, O.B. Bocharov, M.A. Azamatov

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The paper considers borehole wall stability in a junction zone of coaxial wells where a borehole of bigger diameter connects with a smaller one. To determine the shapes and character of rock destruction, 3D poroelastic modeling of the stressed state of the rock around the coaxial junction with account for mudcake formation was performed. The geomechanical model considers the anisotropy of the medium’s deformation properties that are characteristic for the coastal-marine reservoirs of Western Siberia. The rock failure is estimated based on the Mohr-Coulomb criterion with account for tensile destruction condition. The paper considers cases of vertical and inclined junctions of a well drilled at a depth of 2 km in sandstone productive pay with known poroelastic anisotropic properties. The stress and pore pressure analysis has been performed for a mud pressure drop range from 1 to 70 atm and coaxial junctions with different combinations of borehole diameters. The safe mud pressure window has been determined for vertical and inclined junctions. It has been found that the rock failure pattern for junction of bigger diameters is, in general, similar to that for smaller diameters with some insignificant differences in the destruction areas shapes. It has also been demonstrated that in vertical junctions, the bottom holes of smaller diameter are more stable to reduced drilling-mud pressure than the main boreholes, while in the inclined junction it is the main wellbore that is more stable to increased drilling-mud pressure than the bottom hole.
3D poroelastic modeling, coaxial junction, vertical and inclined well, anisotropy, rock failure, sandstone reservoir
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Alexander V. Seryakov
Novosibirsk Technology Center, Baker Hughes
4A Kutateladze st., Novosibirsk, 630090, Russian Federation
Maxim Yu. Podberezhny
22A Sinopskaya emb., St. Petersburg, 191167, Russian Federation
Oleg B. Bocharov
Novosibirsk Technology Center, Baker Hughes
4A Kutateladze st., Novosibirsk, 630090, Russian Federation
Marat A. Azamatov
Salym Petroleum Development N.V.
31 Novinsky boul., Moscow, 123242, Russian Federation

For citation:

Seryakov A.V., Podberezhny M.Yu., Bocharov O.B., Azamatov M.A. (2020). Junction zone stability in coaxial wells of different diameters (on the example of the Khanty-Mansi Autonomous District oil field). Georesursy = Georesources, 22(3), pp. 69–78. DOI: