# A Novel Application of New High-Strength Plugging Agent in Baikouquan Oilfield
## 3 Performance Evaluation by Laboratory Tests
The rheological properties of plugging agent slurries were measured by ZNN-D6 six-speed rotary visometer from Qingdao Jaisona Analytical Instrument Factory. The data for initial gel strength, final shear force, dynamic shear force, plastic viscosity and apparent viscosity of plugging agent slurry were obtained at room temperate. Salt resistance of plugging agent. The plugging slurry with a density of 1.65 g/cm\({}^{3}\) was prepared with different salinities of water. The salinities of water selected in this experiment were 5.0 \(\times\) 10\({}^{4}\) mg/L, 1.0 \(\times\) 10\({}^{5}\) mg/L, 1.5 \(\times\) 10\({}^{5}\) mg/L and 2.0 \(\times\) 10\({}^{5}\) mg/L. The curing temperature was chosen to be 100 \({}^{\circ}\)C. Referring to the procedure of plugging strength, the plugging strength with different salinities was measured. Plugging strength of plugging agent. The plugging strength of the plugging agent varying with temperature and density is shown in Figure 5. The plugging strength of the 1.55 g/cm\({}^{3}\) plugging agent slurry can reach 32 Mpa after curing under the condition of high salinity formation (1.5 \(\times\) 10\({}^{5}\) mg/L) and a temperature of 40 \({}^{\circ}\)C. Under the same conditions, the plugging strength of the plugging agent with a density of 1.75 g/cm\({}^{3}\) is 45 Mpa. The plugging strength increases with the increase in plugging agent density and with the increase in simulated formation temperature. The plugging strength of the plugging agent solidified body continues to increase rather than decrease. In the temperature range of 40-80 \({}^{\circ}\)C, the rising rate of plugging strength increases rapidly, whereas in the temperature range of 80-100 \({}^{\circ}\)C, the rising rate of plugging strength slows down. The rising curve of plugging strength at 100-120 \({}^{\circ}\)C approximates the horizontal line, which indicates that the plugging strength tends to be stable. Among them, the plugging strength of the plugging agent with a density of 1.75 g/mg\({}^{3}\) is 53 MPa at 120 \({}^{\circ}\)C, which can meet the subsequent conventional fracturing operation of a wellbore. The data in the figure are summarized as follows: The plugging strength of the plugging agent with a density of 1.55 g/mg\({}^{3}\) is 32 MPa at 40 \({}^{\circ}\)C. At the moment, the plugging strength of the plugging agent with a density of 1.75 g/mg\({}^{3}\) is 44 MPa. At the same experimental temperature, with the increase in plugging agent density, the plugging strength of the plugging agent increases by 12 MPa. Similarly, the plugging strength increases by 7.5 MPa at 120 \({}^{\circ}\)C. It can be concluded from the above results that the plugging strength of the plugging agent increases with its density and experimental temperature. With the increase in temperature, the rising range of the curve decreases and tends to level. It shows that the plugging agent can maintain high plugging strength in high-temperature conditions. It can meet the plugging requirements. Figure 4: Apparatus for plugging formation simulation. Figure 6 shows the plugging strength of the plugging agent changing with temperature and time. It can be found that the hydration reaction in the plugging agent continued within 15 weeks at 80 \({}^{\circ}\)C, the plugging strength of the plugging agent gradually increased within 15 weeks, and it tended to be stable from 15 weeks to 25 weeks. Similarly, it can be concluded that the hydration reaction of the plugging agent continued within 5 weeks at 100 \({}^{\circ}\)C, and the plugging strength reached a stable state after 5 weeks. As can be seen from the two curves in the figure, the plugging strength at 100 \({}^{\circ}\)C is higher than that at 80 \({}^{\circ}\)C. When temperatures get to 80 \({}^{\circ}\)C and 100 \({}^{\circ}\)C, the curing time reaches 5 weeks and 15 weeks, respectively, in this experimental data. The plugging strength does not change, and it can indicate the structure of the solidified body tends to be stable.