Industrial & Engineering Chemistry Research, Vol.52, No.46, 16352-16363, 2013
Comblike Polyacrylamides as Flooding Agent in Enhanced Oil Recovery
The oil recovery from core material and a specifically designed flow cell using novel branched (comblike) polyacrylamides (PAM) has been investigated. The injectivity characteristics of the different branched PAMs were evaluated by filtration tests and core-flow experiments. The number of arms of the branched PAM has little to no effect on the filterability and permeation through a porous medium. The 13-arm branched PAM displayed a higher residual resistance factor (RRF) in Berea sandstone than its linear analogue and a commercial HPAM. In addition, the thickness of the layer adsorbed at the rock surface is higher for the branched PAM. Oil trapped in dead-end pores is simulated using a 2D flow cell and the effect of the number of arms on the recovery of residual oil is evaluated. In brine solutions, the branched PAMs perform equal or better than their linear analogues in terms of the solution viscosity. The oil recovery of a branched PAM with a similar molecular weight is 3 times as high as that for the commercial polymer. The recovery efficiency, evaluated using low permeable Berea as the porous medium, is significantly improved by using branched PAM instead of linear ones (5.0 compared to 1.5% of the OOIP). An improvement is also observed when high permeable Bentheim cores are used as the porous medium (9.4% compared to 6.0% of the OOIP). The higher oil recovery in the 2D flow cell might explain the improved performance of the branched PAMs. The high thickening capability and the low molecular weight of the branched PAMs makes them suitable for application in enhanced oil recovery (EOR, especially for low permeable reservoirs).