## 4 Numerical Simulation Study of the Effect of Anchoring on Overburden Rock in Oil Wells
### Analysis of Oil Wells Within a Cluster of Wells with Different Burial Depth Pairs  
(1) Stress changes in oil wells at different burial depths  
Through numerical simulation, the maximum principal stress distribution around the oil well was extracted at various burial depths, and its variation trend is illustrated in Figure 7. The results indicate the following:  
* The peak stress increases with increasing burial depth. * At a burial depth of 10 m, the peak stress around the oil well is only 0.37 MPa, with a stress concentration range of less than 1.2 m.
* At a burial depth of 105 m, the peak stress rises to 2.24 MPa, while the stress concentration range expands to 4 m, and the stress concentration zone contracts toward the well wall. At shallow burial depths (10-30 m), the stress concentration zones are more dispersed. However, at greater depths (80-105 m), stress localizes around the wellbore, leading to higher localized stress. Figure 6: Diagram of the oil well excavation process. Figure 7: Cont. As burial depth increases, interactions between adjacent well groups intensify:  
* At shallow depths (10-60 m), no significant stress overlap is observed between wells. * At greater depths (90-105 m), neighboring well stress fields exhibit superposition effects, leading to an expansion of the stress concentration zones. 2. Displacement changes in oil wells at different burial depths The displacement variation in the rock formation surrounding the oil well exhibits the following characteristics as burial depth increases:  
* At a burial depth of 30 m, the displacement influence range is 18 m.
* At a burial depth of 105 m, the displacement influence range expands to 41 m, indicating a larger affected zone and an enhanced constraining effect of the oil well. When the oil wells are shallowly buried (10-60 m), formation subsidence is more pronounced, and the restraining effect of the oil wells on the deformation of the surrounding rock is relatively weak. However, at greater burial depths (80-105 m), the overall formation subsidence decreases, suggesting that oil wells exert a significant inhibiting effect on formation settlement, as shown in Figure 8.  
Figure 7: Stress distribution around oil wells with different burial depths. 3. Changes in plastic zone of oil wells under different burial depths The plastic zone surrounding oil wells is a critical parameter for assessing rock formation damage. Simulation results indicate the following, as shown in Figure 9: * The plastic zone remains limited in extent under all burial depth conditions, ranging between 0.9 m and 1.6 m. * At a burial depth of 105 m, the plastic zone reaches its maximum extent of 1.6 m but does not exhibit significant penetration-induced damage. Figure 8: Plot of the extent of displacement influence around wells of different burial depths. * The plastic zone is primarily localized around the wellbore, with no overlap between plastic zones of adjacent wells, suggesting the absence of stress coupling effects between neighboring wells. Based on the simulation results, the anchoring effect of oil wells intensifies with increasing burial depth, primarily reflected in the expansion of the stress concentration area and the increase in the displacement influence range. For deeply buried oil wells (>80 m), the constraint on stratum subsidence is significantly enhanced, with an influence  
Figure 9: Distribution of plastic zones around oil wells with different burial depths. range extending to 41 m. However, displacement variations in the rock strata immediately surrounding the oil wells are smaller compared to displacement changes at greater distances from the wells. The plastic zone remains stable within a range of 0.9 to 1.6 m, without forming penetrative damage. Based on numerical simulation results, the overburden subsidence in the vicinity of the wellbore is significantly lower than that observed at greater distances. Specifically, strata near the wells exhibit 31-48% less subsidence compared to distal regions.