Drilling fluids play a crucial role in the well drilling process, performing essential functions such as borehole wall stabilization, cuttings removal, and facilitating signal transmission for logging tools. However, during drilling in fractured formations, the penetration of drilling fluid into pore and fracture networks can lead to borehole wall instability, increased permeability, and circulation losses. One promising approach to addressing this issue is the chemical treatment of rock formations to enhance their mechanical strength. This study investigates the effect of chemical additives – zinc sulfate (ZnSO₄) and sodium fluoride (NaF) – on the mechanical properties of carbonate rocks. Experiments were conducted on limestone core samples treated with ZnSO₄ (0.1 M) and NaF (0.1 M and 0.9 M) solutions. The changes in hardness and permeability of the samples were evaluated before and after treatment. The results demonstrated that treatment with ZnSO₄ (0.1 M) led to a 19% increase in limestone hardness and a 76% reduction in permeability, indicating its high effectiveness in carbonate rock strengthening. In contrast, treatment with NaF at a concentration of 0.1 M did not significantly impact the mechanical properties of limestone, while increasing the concentration to 0.9 M resulted in only a slight hardness improvement of 3.8%. Thus, ZnSO₄ proved to be significantly more effective in enhancing the strength of carbonate rocks compared to NaF. The obtained results confirm the feasibility of using chemical treatment to reinforce borehole walls in carbonate formations.

doi.org/10.32737/0005-2531-2026-1-47-55