Stability of boreholes in a geologic medium including the effects of anisotropy

Influence of Bedding Angle on Borehole Stability: A Laboratory Investigation of Transverse Isotropic Oil Shale

“…Several analytical solutions and modeling results exist that predict the stress distribution and borehole collapse or fracture initiation pressures around deviated boreholes in TVI rocks (Aadnoy 1989;Roegiers 1993, 1996;Gupta and Zaman 1999;Pei 2008). The differences between isotropic and TVI rocks are negligible if the borehole axis is oriented normal to bedding.…”

Calculation of collapse pressure in shale gas formation and the influence of formation anisotropy

“…Schematic sketch of the inclined borehole and the transversely isotropic formation ʋ stress field around the wellbore is very complicated, so in this paper the author just directly cites the result of previous researchers. According to the work of researchers such as [5][6][7][8], the stress field around the wellbore provided is given as eq.3, and the detail process can be seen in literature ([7].…”

“…To determine the proper criteria of the rock failure in shale gas formation, the compressive strength was measured on specimens cored at different angles with respect to the normal of the shale bedding plane under different confining pressures. The suitable failure criteria for laminated formation is the continuously variable cohesion strength criterion developed by McLamore [3][4][5][6][7][8][9][10][11][12][13][14], which is expressed in eq.6. According to the experiment result, the constant parameters in eq.6 can be gained with regression method, and the regression result is: A1 = -18.2, A2 = -15.8, B1 = -9.88, B2 = -7.94, ΅ 1 = 47°, Κ = 33.79°, m = 4, n = 4.…”

“…S.H.Ong [7] took into consideration the effect of the nonlinearity and the poroelasticity based on the Aadnoy B S's model. D.Gupta and M.Zaman [8] developed a program to calculate the fracture pressure and collapse pressure of anisotropic formation, and the result shows that the fracture pressure and collapse pressure have a closely relationship with the deviation angle of the wellbore and the formation, the anisotropic degree of the rock material, the in-situ stress state, etc. The weak bedding plane (bedding plane) generally present in the non-isotropic shale gas formation, but previous research about shale gas formation usually focused on the impact of the bedding plane and barely took into consideration both of the anisotropy influence and the impact of the weak bedding plane [9][10][11][12].…”

A wellbore stability analysis model with chemical-mechanical coupling for shale gas reservoirs

“…The results of that study indicated that rocks would fail along weak planes under certain conditions, which had significant effects on wellbore stability. Following Aadnøy, various researchers proposed new methods to determine wellbore stability by assuming that rocks were transversely isotropic materials with anisotropic strength behaviors (Aadnøy and Chenevert, 1987;Aadnøy, 1988;Ong andRoegiers, 1993, 1996;Ong, 1994;Okland and Cook, 1998;Gupta and Zaman, 1999;Zhang, 2008Zhang, , 2009Chen et al, 2008a,b;Pei, 2008;Al-Bazali et al, 2009;Younessi and Rasouli, 2010;Tan et al, 2010;Jin et al, 2013;Hou et al, 2013;Zhang, 2013). Their works indicated that neglecting the effects of anisotropy could result in incorrect results.…”