Experimental Investigation of Viscosity Ratio Effect on Displacement Performance of Polymer Systems During Heavy Oil Recovery

Date
2012-09
Authors
Pantus, Pavlo Volodymyrovych
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Publisher
Faculty of Graduate Studies and Research, University of Regina
Abstract

Heavy oil production during secondary recovery is often plagued by high producing water/oil ratios; this is a direct result of the unfavourable viscosity ratio that leads to viscous instability at the displacement front between the injected water and the more viscous oil. Polymer flooding has proven to be an exceptionally efficient enhanced oil recovery (EOR) technique that increases the stability of the displacing front, accelerating the pore displacement efficiency and improving the vertical and areal macroscale sweep efficiencies. This is especially important in heavy oil reservoirs, where recovery factors tend to be less than 10 % of original-oil-in-place (OOIP) The instability behaviour (viscous fingering) results from the difference in fluid mobilities between the displacing and displaced phases. The impact of viscosity ratio on the polymer EOR process was determined through a set of experiments using an oil-saturated, synthetic glass bead sand-pack in a thin-fracture visual cell. The range of viscosity ratios of 20-, 40- and 80:1 was also evaluated for pressure, oil recovery, and dynamic adsorption response by conducting a series of coreflood tests in synthetic glass beads using conventional hydrolyzed polyacrylamide (HPAM) and hydrophobically associating (HAP) polymer solutions. This thesis provides a new insight regarding oil displacement efficiency from water and polymer solutions using oil viscosities ranging from 22 to 2039 mPa·s. The fracture-model tests provided visual representations of viscous fingering behaviour. It was found that the polymer solutions exhibited much more stable fronts and improved sweep efficiency with far less occurrence of complex shielding, spreading and splitting behaviour in the porous environment. In general, the coreflood tests using the HAP polymer showed faster recovery response with significantly higher resistance factors than HPAM at the same viscosity ratios; however, converse to what is observed with conventional polymer flooding, there was no significant difference in ultimate oil recoveries with either polymer type when flooded with different viscosity ratios. This result suggests that higher concentrations (and higher bulk viscosities) alone may not be as influential a parameter when considering polymer flooding for heavy oil EOR applications.

Description
A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Applied Science in Petroleum Systems Engineering, University of Regina. XIX, 146 p.
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