Abstract
The viscoelastic branched-preformed particle gel (B-PPG) has been successfully applied to enhance oil recovery in mature reservoirs. However, due to a lack of a clear understanding of the transport characteristics of B-PPG in porous media, the injectivity and plugging efficiency are not ideal, and the incremental oil recovery is not as expected, which poses a great obstacle to the large-scale popularization and application of B-PPG in mature oilfields. Thus, the influences of elastic moduli, matching coefficients, and injection rates on transport characteristics of B-PPG in porous media were investigated by conducting core flow experiments. The results indicate that the elastic modulus of B-PPG can significantly affect the injectivity and plugging efficiency. The higher the elastic modulus is, the more difficult it is to transport in the porous medium. When the particle size is similar, as the elastic modulus increases, the resistance factor (F(r)) and residual resistance factor (F(rr)) increase. When the elastic modulus is similar, as the particle size increases, the F(r) and F(rr) increase. As the matching coefficient decreases, the F(r) and F(rr) decrease, reflecting the improvement of injectivity and the weakening of plugging efficiency. The higher the reservoir permeability, the lower the matching coefficient. When the reservoir permeability ranges from 0.30 to 5.30 μm(2), the B-PPG with an elastic modulus of 42.2 Pa and a D(50) of 525 μm can migrate smoothly into the depth of porous media and form effective plugging. As the injection rate increases, the F(r) and F(rr) decrease, reflecting the improvement of injectivity and the weakening of plugging efficiency. Therefore, to achieve good injectivity and plugging efficiency of the B-PPG suspension, the injection rate should be in the range of 0.5 mL·min(-1) to 1.5 mL·min(-1). Hence, these findings could give an important understanding of the factors affecting the transport characteristics of B-PPG and provide guidance for enhancing oil recovery by B-PPG flooding in mature oilfields.