Associated Polymer ASP Flooding Scheme Optimization Design and Field Test after Polymer Flooding in Daqing Oilfield

Abstract

Abstract There are 54 blocks entered into subsequent water flooding period after polymer flooding in Daqing oilfield, The comprehensive water cut is as high as 97.2% and the average oil recovery factor is 57% for the reservoir after polymer flooding, There are 44% geological reserves still remained underground and these reserves are of good quality for further exploitation. But the reservoir has gone through deepen development by tertiary oil recovery and entered into the period of the fourth enhanced oil recovery, so how to further enhance oil recovery is a world's toughest problem. Therefore a new oil displacing system with high efficiency should be developed suitable for the reservoir after polymer flooding in order to greatly enhance oil recovery for ultra-high water cut reservoir after polymer flooding. In this paper, lots of lab experiments have been carried out consisting of oil displacement performance evaluation and formula optimizing. A new ASP formula using associated polymer has been developed, the incremental oil recovery of this system is 10.35% in the lab experiments of natural cores after polymer flooding. In contrast to linear polymer ASP system, associated polymer ASP system can reduce polymer dosage by 48% and increase oil recovery by 3.3% at the same time. The reservoir engineering and oil displacement scenarios have been worked out and the field test has been carried out in the N3D block with 16 injection wells and 25 production wells after polymer flooding in Daqing oilfield. The numerical simulation predicts the incremental oil recovery can reach up to 8.76% after polymer flooding. The test has entered into field and obtained good technological and economic development effect. The blank water flooding began in Sep 2012 and the trial injection of ASP flooding began in Oct 2013 and the main ASP slug began in Jun 2014. Till Oct 2019, the accumulative injection pore volume was 0.9104 PV with the injection pressure increased by 4.7 MPa, water absorption thickness ratio increased by 27.1%, the biggest water cut decline of single well was 6.4% and the staged incremental oil recovery was 7.89%. At present, the accumulative oil production increment is 0.647 million barrels and the economic benefit is 32.35 million dollars. The numerical simulation prediction shows that the final accumulative oil production increment is 0.657 million barrels and the final economic benefit is 32.87 million dollars. This new technology and field test can enhance oil recovery greatly for ultra-high water cut reservoir after polymer flooding and obtain good technological and economic development effect, so it has a broad application prospect and can be applied extensively in ultra-high water cut blocks after polymer flooding in Daqing oilfield.