Gravitational stresses in anisotropic rock masses with inclined strata

Horizontal stress contrast in the shallow marine sediments of the Gulf of Mexico sites Walker Ridge 313 and Atwater Valley 13 and 14 – Geological observations, effects on wellbore stability, and implications for drilling

“…The deepest maximum horizontal stress directions determined from image logs in each well are demarcated on the plot. The stress directions are roughly aligned with the contours of the structure and the maximum horizontal stress coincides with the strike of the dipping beds, consistent with the results of Amadei and Pan (1992). In the vicinity of WR313-G, the structure dips approximately 28 generally toward the northeast.…”

“…However Figure 12 shows that the structure flattens out at the WR313-H location to a dip of about 20 deg. Although other explanations may exist, it seems plausible that a reduction of dip may have caused a decrease in the amount of horizontal stress anisotropy experienced by WR313-H and could explain why this well had far fewer breakouts than WR313-G. That a lessening of dip could reduce horizontal stress anisotropy is consistent with the findings of Amadei and Pan (1992). However quantifying this effect within the context of WR 313 lies beyond the scope of this study.…”

“…the analysis of the drilling-induced fractures in the shallow section of WR313-G. The stress rotation observed with depth could possibly be explained by the work of Amadei and Pan (1992) who modeled stresses in dipping beds under the influence of gravity for the simple cases of zero lateral strains or displacements. For such cases the vertical stress was always a principal stress.…”

Stresses in anisotropic rock masses: an engineering perspective building on geological knowledge

“…The first type of boundary condition, used in Examples 1a-c, is no-lateral strain under a vertical stress of 10 MPa. In this case, the pre-mining state of stress depends on the elastic properties of the rock mass and on the orientation of the symmetry planes as first shown by Wittke [12] for transversely isotropic media, and by Amadei et al [17], Savage et al [18] and Amadei and Pan [19] for generally anisotropic media. Because the plane of transverse isotropy is parallel to x 2 ; axes x 1 ; x 2 ; and x 3 ; are principal stress directions.…”

A 3-D boundary element formulation of viscoelastic media with gravity

“…1 and is assumed to remain constant afterwards. Following the same procedure as in Amadei and Pan (1992) and Pan and Amadei (1996), a very simple and exact closed-form particular solution related to the body force of gravity can be derived. In the Laplace transformed domain, the particular displacements are:…”