## 3 Results and Discussion  
Figures 3-7 reveal the main calculation results obtained by simulating the stress-strain state near the well. \begin{table}
\begin{tabular}{c c c} \hline \hline \(\boldsymbol{\mathsf{N}}\) & **Characteristic** & **Value** \\ \hline
1 & [PERSON]’s modulus, GPa & 11.3 \\
2 & Poisson’s ratio, d.f. & 0.179 \\
3 & Compressive strength, MPa & 31.5 \\
4 & Angle of internal friction, \({}^{\circ}\) & 29.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Elastic strength characteristics of cement stone. \begin{table}
\begin{tabular}{c c c} \hline \hline \(\boldsymbol{\mathsf{N}}\) & **Characteristic** & **Value** \\ \hline
1 & Young’s modulus, GPa & 9.4 \\
2 & Poisson’s ratio, d.f. & 0.32 \\
3 & Biot coefficient, d.f. & 0.75 \\
4 & The average depth of the & 1489 \\
5 & Initial reservoir pressure, MPa & 14.5 \\
6 & Differential pressure & 0–12 \\
7 & drawdown, MPa & 36.3 \\
8 & Angle of internal friction, \({}^{\circ}\) & 25 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Characteristics of a productive object used in calculations. Figure 2: Dependence of permeability on average effective stresses. Figure 4: Safety factor of the cement stone with a differential pressure drawdown of 0 MPa (**a**), 3 MPa (**b**), 6 MPa (**c**), and 9 MPa (**d**). Figure 3: Safety factor of the casing with a differential pressure drawdown of 0 MPa (**a**), 3 MPa (**b**), 6 MPa (**c**), and 9 MPa (**d**). Figure 5: Change in rock permeability (in %) in relation to the initial value with the initial reservoir pressure and differential pressure drawdown of 0 MPa (**a**), 3 MPa (**b**), 6 MPa (**c**), and 9 MPa (**d**). Figure 6: Visualization of possible zones of rock destruction on the basis of the Mohr–Coulomb criterion with a differential pressure drawdown of 0 MPa (**a**), 3 MPa (**b**), 6 MPa (**c**), and 9 MPa (**d**). The green color indicates tensile stress areas, red color indicates compressive stress areas, blue color indicates nonstress areas (without units of measurement). In order to analyze stresses for the steel casing and cement stone, we determined a safety factor from the following equations:  
* For the casing, \[k_{c}=\frac{\sigma_{\rm Y}}{\sigma_{1}},\text{ safety factor of the casing}\] (9) where \(\sigma_{\rm Y}\) is the yield strength of steel; \(\sigma_{1}\) is the maximum main stress. * For the cement stone, \[k_{st}=\frac{\sigma_{3}(\frac{1+sin}{1-sin})+\sigma_{UCS}}{\sigma_{1}},\text { safety factor of the cement stone}\] (10) where \(\sigma_{\rm UCS}\) is the tensile strength of cement stone under uniaxial compression. Figure 3 proves that the casing remains stable regardless of the pressure drawdown, and the safety factor reaches 3-4 units. It should also be noted that the zones of increased and decreased stresses occur near the perforation channel. Highly stressed zones are located in the upper and lower parts of the perforation (Figure 3a). In these parts, the safety factor is significantly reduced and close to one unit, indicating that casing integrity damage may occur. At the same time, these parts are quite small and are located at a distance comparable to the radius of the perforation. On the contrary, the zones of decreased stresses arise in the lateral parts of the perforations, where the safety factor reaches 32 units; although, these parts are also quite small. The safety factor distribution for the cement stone differs due to its distinct elastic strength properties (Figure 4). Figure 4 indicates that depending on the differential pressure drawdown, the safety factor of cement stone varies from about 2 to 3 units. The lowest value of this parameter is concentrated near the perforation channels and represents 1.35 units. It is important to note that, with an increase in the pressure drawdown, the maximum safety factor increases, while the minimum one decreases. The maximum value of this parameter is concentrated on the outer surface of the cement stone in contact with rocks, as well as on the upper and lower surfaces of the perforation channel.