The Experimental Research On The Influences On The Displacement Efficiency Of Polymer Slug Combinations

Polymer flooding technology has been used extensively. Recently, polymer can not only enlarge volume sweeping but also increasing displacement efficiency in EOR aspect demonstrated through the researches on the mechanism of viscoelasticity carried out by some specialists in home. In the polymer flooding, various amount of polymer gains different flooding effect, and so does different slug-concentrations of polymer in the same amount of polymer. So it is important for carrying out polymer flooding project to select the amount and concentration of polymer.Based on the therapies of polymer flooding, measure the viscoelasticity of two typical kinds of polymers used in Daqing Oil Field, which are called common mid-molecular weight polymer and salt-resistance polymer. Combining with practical situation in the spot, we have drawn up multi-slug flooding systems, and done the researches on effects of the different slug combinations on the displacement efficiency under the different conditions, the same amount of polymer injected and the same concentration of it. Finally, we carried out the projects on the three-pipe parallel connection in order to research the influences of flooding systems after injecting vavious slugs on the recovery in the heterogeneous condition.It concluded that, the higher concentration and molecular weight are, the higher the viscoelasticity is. Under the same amount of polymer, the multi-slug flooding system with the polymer concentration of 2000 mg/L has better flooding effect. Various slug volume and slug concentration of polymer had less influences on the chemical recovery even total recovery. Under the same size of polymer slug, the compound mode of slug with the polymer concentration of 2500 mg/L has better flooding effect. From the three-pipe parallel connection experiments, increasing the concentration injected can enhance the volume sweeping and displacement efficiency so as to enhance the recovery of each oil layers and entire reservoir. These conclusions can provide experimental foundations for the polymer flooding in transition zone at the late stage of polymer injection, which also guide for the production and practice in oil field.