Study On Stability Of The Viscosity Of Polymer Solution For Flooding

Polymer flooding of EOR is more and more widely used in oilfield at domestic and abroad. The viscosity and its stability of HPAM solution are important factors that influence the effect of polymer flooding. So it is significant in EOR through investigating the viscosity and its stability of HPAM solution and taking actions to raise them. In this paper, environmental factors influenced the initial viscosity of HPAM solution, for example the style and concentration of negative ion and positive ion, are researched in the lab. Experiment shows that positive ions are the main factors, especially multivalent cations. At equal molar concentration, the order of positive ions affecting the initial viscosity of HPAM solution is Fe²⁺>Fe³⁺>Ca²⁺>Mg²⁺>Na⁺ (K⁺). While negative ions have minor influence and the order is Cl^-(NO₃^-)>SO₄^2-(NO₂^-)>HCO₃^-(SO₃^2-)>CO₃^2-. This paper also researches the factors affecting the stability of the viscosity of HPAM solution. And results show that the main factors are dissolved oxygen, multivalent cations (especially Fe²⁺ and Fe³⁺). Negative ions have some influence and the order is SO₄^2->(Cl^-, NO₃^-)>CO₃^2->(HCO₃^-, NO₂^-)>SO₃^2-. The mechanism of the factors affecting the viscosity and its stability of HPAM solution is analyzed. In the end, addition agent SC-1 and WN which can raise the viscosity and its stability are developed and tested with oil produced water from Shengli Oilfield. The viscosity and its stability of HPAM solution are improved with SC-1 and WN. The initial viscosity is raised by 13.2mPa·s and the reserve rate of the viscosity is 68.8%. Experiment result shows that addition agent SC-1 and WN can effectively improve the viscosity and its stability.