Study on the Variation of Resistance Factor of Polymer Microspheres with Distance from the Injection Well

When mobility control agents migrate over long distances in reservoirs, their mobility control ability varies with the distance from the injection well owing to shear degradation, adsorption, and retention. The mobility control ability of a chemical agent is commonly quantified using the resistance factor (RF). To investigate the variation in the RF with migration distance from an injection well, an 18-m-long artificial core was divided into ten segments herein, and the RFs of a polymer solution (partially hydrolyzed polyacrylamide; HPAM) and a polymer microsphere (PM) dispersion system flowing through each segment were independently measured. Experimental results showed that with increasing migration distance, the hydrodynamic radius (D _h) and the RF of HPAM decreased continuously. Conversely, the particle size (d) and the RF of PMs initially increased and then decreased. Based on the observed RF variation, a dependency relationship was established between the RF and four parameters: the maximum resistance factor (RF_M), migration distance (L), distance to peak RF (L ₀), and decay coefficient (ω). Further analysis revealed that increasing the injection rate from 0.3 to 0.7 mL min^-1 reduced the RF_M of PMs from 29.7 to 24.6, and increased L ₀ from 7.2 to 14.4 m and ω from 0.0166 to 0.0271 m^-1, indicating a faster decline in the RF. Consequently, the projected RF at 100 m from the injection well (RF₁₀₀) decreased from 7.1 to 3.3. When the PM concentration increased from 0.2 to 0.4 wt %, the RF_M of the surfactant/polymer microsphere (S/PM) system increased from 16.2 to 41.3, L ₀ remained constant at 10.8 m, ω increased from 0.0151 to 0.0179 m^-1, and the projected RF₁₀₀ increased from 5.0 to 9.2. When the migration distance L > 17.1 m, the projected RF of the S/PM system exceeded that of the PM system, with a projected RF₁₀₀ difference of 2.3. These results demonstrated that the addition of surfactant extended the effective range of PMs. The proposed method provides a new approach for optimizing the selection and design of chemical mobility control agents.