Problems associated with the instability of the wellbore annually cost the oil and gas industry billions of dollars around the world. However, the application of geomechanical models can significantly reduce these costs. Geomechanical models can be built based on mechanical constitutive laws (elastic, poroelastic, elastoplastic and etc.) and failure criterion of material (Mohr – Coulomb, Mogi – Coulomb and etc.). Selection of an appropriate failure criterion is crucial in wellbore stability analysis. The Mogi – Coulomb criterion is applied in this work to calculate shear failure. The objective of this paper is to investigate the pore pressure and temperature effects on elastic deformations and resultant mechanical instabilities in the near wellbore zone. The results are compared with the case wherein the pore pressure and temperature effects are ignored. Accordingly, minimum required rock strength for safe drilling and stable well trajectory are estimated. It is shown that the coupled porothermoelastic model better cover the physics of mechanical wellbore instability problems and neglecting heating and cooling effects might cause to fallacious results. To verify our results, the proposed approach is applied to analyze the stability of a vertical wellbore drilled in an oil field in Siberia, Russia.
References
1. Zoback M.D., Reservoir geomechanics, Cambridge: Cambridge University Press, 2007.
2. Etchecopar A., Vasseur G., Daignieres M., An inverse problem in microtectonics for the determination of stress tensors from fault striation analysis, Journal of Structural Geology, 1981, V. 3 (1), pp. 51–65.
3. Qian W., Pedersen L.B., Inversion of borehole breakout orientation data, Journal of Geophysical Research: Solid Earth, 1991, V. 96 (B12), pp. 20093–20107.
4. Al-Ajmi A.M., Zimmerman R.W., Relation between the Mogi and the Coulomb failure criteria, International Journal of Rock Mechanics and Mining Sciences, 2005, V. 42 (3), pp. 431–439.
5. Zimmerman R.W., Al-Ajmi A.M., Stability analysis of deviated boreholes using the Mogi-Coulomb failure criterion, with applications to some North Sea and Indonesian reservoirs, SPE 104035-MS, 2006.
6. Garavand A., Rebetskiy Yu.L., Methods of geomechanics and tectonophysics in solving the problems of stability of oil wells during drilling (In Russ.), Geofizicheskie issledovaniya = Geophysical Research, 2018, V. 19 (1), pp. 55–76.
7. Zoback M.D., Moos D., Mastin L., Anderson R.N., Well bore breakouts and in situ stress, Journal of Geophysical Research: Solid Earth, 1985, V. 90(B7), pp. 5523–5530.
8. Meier T., Rybacki E., Reinicke A., Dresen G., Influence of borehole diameter on the formation of borehole breakouts in black shale, International Journal of Rock Mechanics and Mining Sciences, 2013, V. 62, pp. 74–85.
9. Carslaw H.S., Jaeger J.C., Conduction of heat in solid, Oxford; Clarendon Press, 1959.
10. Wang Y., Papamichos E., Conductive heat flow and thermally induced fluid flow around a well bore in a poroelastic medium, Water Resources Research, 1994, V. 30 (12), pp. 3375–3384.
11. Ghasemi M.F. et al., Coupled Thermo-Poro-Elastic modeling of near wellbore zone with stress dependent porous material properties, Journal of Natural Gas Science and Engineering, 2018, V. 52, pp. 559–574.
12. Kirsch E.G., Die theorie der elastizität und die bedürfnisse der festigkeitslehre, Zeitschrift des Vereines deutscher Ingenieure, 1898, V. 29, pp. 797–807.
13. Detournay E., Cheng AHD, Poroelastic response of a borehole in a non-hydrostatic stress field, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 1988, V. 25 (3), pp. 171–182.
14. Tao Q, Ghassemi A., Poro-thermoelastic borehole stress analysis for determination of the in situ stress and rock strength, Geothermics, 2010, V. 39(3), pp. 250–259.
