Effect of Heterogeneity on Injection-Production Dynamic Characteristics of Polymer Flooding in Offshore Fields

Abstract

Aiming at the problems of fluid production decline and production release difficulty in polymer flooding process in Bohai Oilfield, through indoor physical simulation, the compatibility between polymer and target reservoir permeability was studied. Also, the effects of reservoir heterogeneity on injection capacity, fluid production variation, diversion rate and oil displacement effect of polymer flooding were studied through three-plate parallel core experiment. The results show that the resistance coefficient and residual resistance coefficient increase with the increase of polymer concentration and the decrease of reservoir permeability. When the polymer concentration is 1750 mg/L and 2500 mg/L, the corresponding permeability limits are 2000 × 10−3 μm2 and 4000 × 10−3 μm2, respectively. The heterogeneity of reservoir has a great influence on profile inversion timing and injection-production capacity of polymer flooding. When the permeability ratio of reservoir is 6 times and 10 times, the compatibility between polymer and high permeability layer is better than that between medium and low permeability layer. The timing of profile inversion is earlier, the diversion ratio of medium and low permeability layer is smaller, and the sweep area is smaller, the recovery is low. When the permeability gradient is 3 times, the polymer has good compatibility with high and medium permeability layers. Effective plugging of high and medium permeability layers can be formed, the diversion rate and fluid absorption of low permeability layers increase, the sweep area of low permeability layers increases, the fluid production rate is stable and the ultimate recovery rate is high. It indicates that the adaptability of reservoir heterogeneity to polymer flooding solution is very important for oil recovery.KeywordsReservoir heterogeneityPolymer floodingCompatibilityDiversion rateOil displacement effect