Potential of Welan gum to enhance oil recovery

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.

The biopolymer produced by Rhizobium viscosum CECT 908 is a promising agent for application in microbial enhanced oil recovery

“…In order to characterize the rheological behaviour of the biopolymer studied here, the effect of shear rate on shear stress and the apparent viscosity was determined. The R. viscosum biopolymer exhibited a pseudoplastic or shear-thinning behaviour, as previously reported for other biopolymers such as xanthan gum, diutan gum and welan gum [4,8,9,12,36,37]. For this type of (bio)polymer, as the shear rate increases, the apparent viscosity decreases and the shear stress increases.…”

“…The viscosity of the biopolymer produced by Pseudomonas oleovorans was significantly reduced when exposed to 100°C for 1 h, but was not affected by temperatures up to 80°C [36,39]. In contrast, xanthan gum, welan gum and HPAM exhibited a considerable loss of viscosity between 75°C and 85°C [8,9,12,27].…”

“…A shear-thinning behaviour favours (bio)polymer application in EOR, because during their injection in the oil reservoir, they undergo high shear rates (≥ 100 s −1 ) in the near-wellbore region, which results in low viscosity values, improving their injectivity and preventing damage to the oil formation. Once transported away from the near-wellbore region, the shear rate experienced by the (bio) polymer solution is lower (about 1 to 10 s −1 ), allowing the recovery of high viscosity values, required for a favourable mobility control and, consequently, an efficient oil displacement [9,13]. However, the high shear rates achieved during the injection of the (bio)polymer solution can result in the mechanical breakdown of the molecules due to the high shear stress values achieved [3,14].…”

“…In order to study the stability of the biopolymers over the time when subjected to shear rates representative of oil reservoirs, thixotropic studies were performed according to the methodology proposed in [12]. Purified R. viscosum CECT 908 biopolymer and xanthan gum (both at 2 g/L) were exposed to a constant shear rate (7.3 s −1 ) at 40°C for 2 h. The shear rate used was selected according to similar literature reports as being representative of oil reservoir conditions [4,9,12,31,32]. In order to prevent evaporation of the samples during the assays, their outer surface was covered with silicon oil.…”

“…However, some of these synthetic polymers are hazardous to the environment due to the toxicity of certain compounds resulting from their degradation (e.g. acrylamides) [3,[9][10][11][12]. Moreover, in some cases their application is limited by their instability at the oil reservoir conditions.…”