Research on “Plugging, Adjusting, Driving and Controlling” Adjustment Technology for Polymer Flooding in Class I Reservoirs of Daqing Oilfield

In the PI1–4 oil layers of the Daqing Oilfield, more than 40% of the reserves remain unproduced after polymer flooding, which represents the main potential for subsequent development. In response to the above-mentioned issues, a research on the “adjustment, plugging, flooding, control” adjustment technology of alkali-free ASP flooding after polymer flooding has been carried out. The alkali-free ASP flooding system is a new type of oil displacement system formed by replacing sodium carbonate with sodium chloride. In this paper, through a combination of laboratory experiments and on-site dynamic analysis, the “adjustment, plugging, flooding, control” adjustment technology under this system is proposed and its feasibility is demonstrated. The research results indicate that: “Adjustment on the one hand, there is tracking and adjustment at the injection end. The injection pressure is kept stable through viscosity and testing adjustments to suppress the breakthrough of the injected agent. Secondly, the profile is adjusted. For un-stratified wells, exploration is carried out to determine whether they meet the conditions for stratification. Mechanical stratification should be implemented as early as possible to enhance the utilization of the top of thick oil layers and alleviate inter-layer contradictions; “Plugging” it mainly involves conducting secondary profile control on wells with high injection parameters to block high-permeability layers and mitigate inefficient and ineffective circulation; “Flooding” based on the “adjustment”, the viscosity of the effective well group is reduced and the speed is increased, enabling the oil displacement system to contact more remaining oil and further exerting the displacement and oil washing effects. At the production end, the parameters are adjusted upwards to increase the production pressure difference, promoting effectiveness through strong displacement and washing; “Control” it refers to the control at both the injection and production ends to reduce breakthrough. At the injection end, layer shutdown and injection rate reduction are adopted to control the breakthrough in high-permeability layers. At the production end, planar well shut-in is carried out to control the flowing pressure and prevent the breakthrough of injected agents.Through field tests, the application of this technology in 2024 led to a 1.57% reduction in water cut after polymer flooding and a 1.12% increase in oil recovery.