Borehole damaging under thermo-mechanical loading in the RN-15/IDDP-2 deep well: towards validation of numerical modeling using logging images

Geothermal Energy

Science – Society – Technology

Table 4 Results of the analytical approach for breakouts

Name	Principal stress in the 2D plane perpendicular to the well		Breakout characteristics
	Principal stress in the 2D plane perpendicular to the well		P_well = 0 MPa		P_well = 34 MPa
	σ_A* (MPa)	σ_B* (MPa)	σ_{90°, R = r} (MPa)	r_{θ = 90°,} σ_θ = UCS (cm)	σ_{90°, R = r} (MPa)	r_{θ = 90°,} σ_θ=UCS (cm)
Case A	76	134	326	14.8	292	13.6
Case B	60	79	175	< R	141	< R
Case C	76	178	459	23.0	425	21.0
Case D	80	94	200	< R	166	< R

The computation of the borehole potential damage is linked to no to low wellbore fluid pressure (P_well). σ_90°, R = r is the circumferential stress at the wellbore boundary in the direction of the minimal 2D stress, r_θ =90°, σ_θ = UCS is the distance from the wellbore center where the circumferential stress is equal to the UCS of the dolerite (214 MPa), in the direction of the minimal 2D stress, R is the radius of the borehole. Principal stresses in the cross section perpendicular to the well are obtained by diagonalization of the stress state (σ_ss, σ_dd, τ_sd) mentioned in Table 1 and are thus slightly different from horizontal principal stresses