Abstract:

After long-term exploitation of the high-temperature heterogeneous reservoirs in North China Oilfield, the water content becomes high and the heterogeneity is further enhanced, while conventional chemical flooding measures have poor effects in water control and enhancement of oil production. To solve this problem, the high-temperature resistance and the effects in profile control, water control and oil increase for polymer gels were studied through the combination of indoor screening, physical simulation, and theoretical analysis. The results showed that, the selected gel system had excellent high-temperature resistance and viscoelasticity, and the maximum viscosity was 4 371.2 mPa·s after complete gelation. After 30 days of high temperature aging, the viscosity retention rate was 90.5%, and the elastic modulus and viscous modulus were 10.4 and 1.3 Pa, respectively. The system had strong plugging ability. In a certain range of permeability contrast, the abilities of profile improvement, water control and enhancement of oil production of the system were increased with the increase of permeability contrast. When the permeability contrast was increased from 2.13 to 8.16, the profile improvement rate after profile control was increased from 58% to 92.8%; when the permeability contrast was increased from 2.06 to 8.08, the recovery rate after profile control and flooding was increased from 10.2% to 19.5%.

Key words: high-temperature heterogeneous reservoir, polymer gel, cross-linking mechanism, profile control and flooding, recovery rate