The Study on Enhanced Oil Recovery Technology in Reservoirs after Polymer Flooding

Enhanced oil recovery technology is studied in reservoirs after polymer flooding by laboratory experimentation and field test. The enhanced oil recovery is 17.6%-20.1% by surfactant/polymer flooding in laboratory, more than that of polymer flooding (11%-15%) or surfactant flooding (about 3%), more than the sum of polymer flooding and surfactant flooding, more than the economic equivalent polymer flooding. The oil production increased farther and the water cut decreased farther in zone Ng3-6 of Zhong-1 unit of Gudao oilfield and the sixth unit of Gudong oilfield after surfactant/polymer flooding once polymer injection finished. The viscosity and the elastic modulus increased and the relative azimuth decreased when PPG (Preformed Particle Gel) added into the polymer solution. The PPG/polymer system trend to elastic and could modify the injection profile evidently. The PPG/polymer flooding was put into practice in zone Ng3 of Zhong-1 unit of Gudao oilfield in Feb, 2009. By the end of May, the injection pressure went 1.4 MPa up and the vertical water intake turned to uniform.