Effect of Specific Ions in Preparing Water on Viscosity of Polyacrylamide Solution

Abstract

Served as polymer flooding for the enhanced oil recovery, partially hydrolyzed polyacrylamide (PAM) has widely been employed for the oil production. The PAM solution prepared by the ground clean water was characterized with a higher viscosity in the early years while one, made by the oilfield produced water in the existence of complicated constituents, features a worse viscosity in the recent operation. In the practical opinion, the viscosity is an important indicator of the polymer flooding. The high viscosity of aqueous PAM solution has being pursued for a goal of the successful operation. For the reason, this research objective could be set toward seeking the causes of the viscosity degradation. In this paper, specific ions in the preparing water on effects of the PAM viscosity were identified and evaluated by the analysis of produced water quality used by the operation of preparation in Daqing oilfield. Effects of the specific ions on PAM viscosity were investigated in the lab test for understanding and controlling the viscosity. The results show that the dominant specific ions were found out to consist of the divalent cation (Ca2+and Mg2+), trivalent cation (Al3+), divalent ferrous ion (Fe2+) and divalent sulfide ion (S2-) by means of the data and related chemical theory. Much notable viscosity degradation of PAM solutions was observed in the degree-viscosity curves as the role of most of the specific ion factors. Totally, the retention rate of the viscosity was obviously lowered with the extension of the specific ion by degrees. By the results, the mechanism of the viscosity degradation was briefly proposed and discussed. These data can be provided and suitably specified for the benefit of polymer flooding production.