Lessons Learned From Polymer Flooding Field Application And Challenges After Polymer Flooding In Daqing Oilfield

Summary Polymer flooding has been applied in Daqing Oilfield since 1995, and has been successfully used for 30 years, the peak annual oil production has exceeded 10 million tons for 14 years. This paper presents the experiences of applications of polymer flooding, the key reservoir engineering technologies ensuring successful application of polymer flooding, and the challenge to further improve oil recovery after polymer flooding. Daqing Oilfield has abundant field development data of polymer flooding, including sealed coring well data, well logging data, field production data, and EOR field pilot data. By using these precious first-hand data comprehensively, this paper evaluated the successful experiences, revealed the oil recovery potential, developed a series of key reservoir engineering technologies for polymer flooding, and investigated the challenge and method to further increase oil recovery after polymer flooding. The analysis of the sealed coring well data and production surveillance data revealed that polymer flooding not only increases swept volume, but also improves oil displacement efficiency. The analysis on field development data suggests that, in order to efficiently develop sandstone reservoirs with multiple pay zones and strong heterogeneity, the polymer solution should enable equilibrium displacement and simultaneous response of all pay zones. Accordingly, a method for matching the polymer molecular weight with reservoir properties is established to ensure polymer solutions are injected into reservoirs with different permeability evenly. Moreover, the key reservoir engineering technologies for field application of polymer flooding are developed, including target reservoir configuration, scenario design, and improving performance method. The research results show that reservoir properties changed greatly after polymer flooding, resulting in that water preferential flow channels formed, its thickness percentage is only 15.9%, but its water injection percentage is high up to 60%, indicating that the biggest challenge to further improve oil recovery after polymer flooding is how to overcome futile cycle of displacing fluid in the water preferential flow channels. A new chemical flooding technology has been successfully developed and applied to the pilot of post-polymer flooding, having ability to increase the oil recovery by 15% after polymer flooding. With the application of the technologies in Daqing Oilfield, the oil recovery of polymer flooding is increased by 14% over water flooding, and the new chemical flooding technology has been successfully developed for field application of post-polymer flooding, showing that these research results have a certain reference value to field application of polymer flooding in the other oil field in the world.