Wellbore orientation

At any point along the trajectory of a deviated wellbore, the tangent orientation permits defining wellbore azimuth $\delta$ and deviation $\varphi$ (Fig. 6.19). Azimuth $\delta$ is the angle between the projection of the trajectory on a horizontal plane and the North. Deviation $\varphi$ is the angle between a vertical line and the trajectory. These two variables can be plotted in a half-hemisphere projection plot (stereonet). Notice that a point in this plot represents just one point along a wellbore trajectory. Fig. 6.19 shows an example of the full trajectory of a wellbore.

Figure 6.19: Convention for plotting the orientation of a deviated wellbore on a lower hemisphere projection. The example shows the deviation survey for a real wellbore (radius amplified to highlight small deviations). Notice that it starts slightly deviated on surface and then turns into vertical direction at depth.

PROBLEM 6.4: Consider a place where vertical stress $S_v$ is a principal stress and the maximum horizontal stress acts in E-W direction.

1. Find the planes with maximum stress anisotropy for normal faulting, strike-slip, and reverse faulting stress regimes.
2. Plot the orientation of wellbores in those planes of maximum stress anisotropy in a stereonet projection plot.
3. Where around the wellbore would breakouts and tensile fractures occur in each case?

SOLUTION
The solution below shows just one of the possible solutions for horizontal wells.