Oil Displacement Efficiency and Performance Evaluation of Composite Ion Profile Control Agents Prepared with Oilfield Sewage

摘要

According to the demand of development in Daqing oil field, in order to reduce sewage discharge and save clean water, most of the polymer injection stations have switched to polymer solution diluted by sewage. Considering the present development trend of the oil field and requirement in terms of cost control, we should further deepen the research of formulas for all kinds of chemical sewage. Performance evaluating experiments on the long-term stability, the anti-shear property, the compatibility with initial rock debris and alkali ternary combination system of profile control agents, as well as the test for the efficiency of core displacement physical simulation of profile control and oil displacement evaluation are carried in this paper, which are intended for the composite ion profile control system that are prepared with oilfield sewage. In this paper, the long-term stable composite ion profile control agents formular prepared with oilfield sewage have been determined; the profile control effect of composite ion profile control agents prepared with sewage for cores with different permeability have been presented, and the rules of composite ion profile control agents prepared with sewage on oil displacement effect at different injection time and injection rate have been studied. Research shows that the long-term heat stability, anti-shear property, compatibility with initial rock debris and alkali ternary combination system of composite ion profile control agents prepared with sewage are well, as well as the core plugging effect and anti-corrosion performance. Oil displacement results are obviously different when profile control agents are injected at different time. Injecting profile control agents before polymer flooding works best, medium term secondly, and late stage thirdly. At the same time, the enhanced recovery rate increases with increased profile control agents injection. While the increase of enhanced oil recovery rate becomes slower when the profile control agents injection reach 0.1 PV. After profile control measures are taken, the average injection pressure and starting pressure has risen respectively by 2.7 Mpa and 2.6 Mpa; the water absorbing capacity of high permeable formation has been under control; the water absorbing capacity of low permeable formation has been strengthened; the absorbing water thickness of all wells have been increased; the breakthrough of flooded fluid in certain direction have been solved, which leads to more even polymer forward.