Research On The Association Degree Of Salt-resistance Polymer And Its Adaptability With Reservoir

So far, most oilfields at home have successively stepped into the development stage of high water cut or ultra-high water cut. The phenomenonce of low efficient circulation of injection water becomes gradually serious. So it is urgent to take technical measures to enhance oil recovery efficiency by a large extent. The technology of polymer flooding has attracted wide attention in petroleum industry because of its relatively simple process equipment, lower cost of agents and better effect of enhancing oil recovery efficiency. The technology has been applied on Daqing Oilfield, Shengli Oilfield and Bohai Oilfield, and its technical-economic effect is obvious. As the technology of polymer flooding is spread to the promotion on the oilfields of high temperature and salinity, common polymer can hardly meet the technical requirement of increasing viscosity. Therefore, a series of polymer production with the property of temperature-resistance and salt-resistance have been put into the research both at the lab and on the pilot. And better effect of oil production increment and water cut declination is obtained. However existing polymer of salt-resistance and temperature-resistance get larger viscosity in the condition of high salinity by changing polymer molecule aggregation, which results in the worse adaptability between polymer molecule and the reservoir. Correspondingly, the effect of oil production increment and water cut declination is impaired.In the view of actual demand on the oilfield, the thesis takes geology and fluid characteristics of certain reservoir on Daqing Oilfield as research object, and carries out the study on the influence of modifier β-CD on the viscosity, rheology, viscoelasticity, molecule thread size, molecule aggregation, flow characteristic, transmission migration features and oil displacement efficiency of salt-resistance polymer. And its mechanism is analyzed and discussed. Results show that compared with common polymer, salt-resistance polymer molecule aggregation appears as net structure. Its molecule thread size is larger. The capacity of hydrone envelopment is stronger and so is the capacity of increasing viscosity of polymer solution. β-cyclodextrin has special molecule structure which can screen the hydrophobic groupings of polymer molecule chains. Such restrain can reduce the size of polymer molecule aggregation and enlarge the range of permeability which is adapted by salt-resistance polymer. However, the ratio of “DΦ/Dh” still remains 8-12. Theoretical analysis and practice indicate that polymer solution should give consideration to both sides of plugging the layers of high permeability and diverting to the layers of low and medium permeability. It is not advisable to increase polymer viscosity through changing molecule aggregation because the adaptability also gets worse. For specific reservoir, better effect of oil production increment and water cut declination is obtained by adjusting the association degree of hydrophobic grouping of salt-resistance polymer.