Experimental Study of Polymer Flooding in Low-Viscosity Oil Using One-Quarter Five-Spot Glass Micromodel

Abstract

A polymer flooding technique is developed to reduce the amount of residual oil saturation that cannot be recovered through waterflooding or gas injection processes. Using polymer flooding in the case of high-viscosity oil has been successful due to reducing mobility ratio (M), whereas there is conflict in efficiency of polymer flooding in the case of low-viscosity oil. In this study, to investigate the behavior of polymer flooding in low-viscosity oil, the transparent materials (glass) were used to construct a micromodel and to study various aspects of micro-displacement. By using a micromodel, the displacement of the fluid and menisci was observed and investigated with the aid of images captured by a camera. In this work, two kinds of quarter five-spot glass micromodel patterns were designed and developed and considered as pores medium. These patterns were saturated with light and low-viscosity oil samples from an Iranian fractured reservoir and then flooded by a polymer slug in low-pressure and low-temperature conditions. Three polymer types, hydrolyzed polyacrylamide (HPAM 25%), very low hydrolyzed polyacrylamide (<5%; PA) and xanthan, were utilized to inspect the effects of polymer type, concentration, injection rate, pore structure, and presence of connate water on recovery of low-viscosity oil. The results of experiments illustrated that recovery from HPAM is higher than both xanthan and very low hydrolyzed polyacrylamide. Rate sensitivity tests showed that increasing rate injection induced a decrease in recovery. Flooding in two different micromodel patterns demonstrated that higher permeability leads to lower recovery. In addition, experiments indicated that the presence of connate water caused a reduction in recovery. Finally, compared with waterflooding, polymer flooding resulted in a considerable growth in ultimate oil recovery.