After a pilot site meets the screening qualifications for polymer flooding, the injection measures and the injection formula are key points when designing a polymer flood. This paper places special emphasis on some new design factors that were found to be important during extensive experience during polymer flooding. These factors include (1) recognizing when profile modification is needed before polymer injection and when zone isolation is of value during polymer injection, (2) establishing the optimum polymer formulations, injection rates, and individual well production allocations, and (3) time-dependent variation of the molecular weight of the polymer used in the injected slugs,
At Daqing, polymers with molecular weights from 12 to 38 million Daltons were designed and supplied to meet the requirements for different reservoir geological conditions. The optimum polymer injection volume varied around 0.7 pore volume (PV),1 depending on the water cut in the different flooding units. The average polymer concentration was designed about 1,000 mg/L, but for an individual injection station, it could be much more.2,3 The injection rate should be less than 0.2 PV/yr, depending on well spacing. Additionally, the project design should follow certain rules when allocating the injection rate and production rate for individual wells.