Abstract
Polymer flooding is the most successful chemical enhanced oil recovery method. Large-scale commercial polymer flooding projects are being carried out in China. However, partially hydrolyzed polyacrylamide, the commonly-used polymer for polymer flooding projects is very sensitive to sodium and calcium ions. This limits the field applications of polymer flooding method. The industry longs for a polymer that can tolerate salinity and heat. Welan gum (WLG) is a promising biopolymer because of its performance under challenging conditions. This paper investigates the factors that influence the viscosity of Welan gum solution. Tests show that WLG maintains high viscosity under the attacks of sodium ion, calcium ion, high temperature and long-term heating. Core flooding tests reveal that WLG cannot effectively reduce residual oil saturation, but can reduce the time to reach residual oil saturation.
Highlights
Certain chemicals, such as polymers and surfactants, can be injected into reservoirs to improve oil recovery (Sheng 2010; Gao 2011)
CaCl2 was added to Welan gum (WLG) solution to test its tolerance for calcium ions
The relationships between viscosity and shear rates closely follow linear trends on log–log plot. This reveals that WLG solution is a non-Newtonian fluid
Summary
Certain chemicals, such as polymers and surfactants, can be injected into reservoirs to improve oil recovery (Sheng 2010; Gao 2011). Polymer flooding is the most successful chemical EOR method. Large-scale polymer flooding projects are being carried out in China (Gao et al 2014). This method is being tried in Angola and Brazil
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