The synthetic water-soluble
polymer, partially hydrolyzed polyacrylamide
(HPAM), has been most widely used for enhanced oil recovery (EOR);
however, its poor thermal stability and weak salt tolerance impede
further application in high-temperature and high-salinity oil reservoirs.
To address such deficiencies, three polysaccharides, xanthan gum,
diutan gum, and scleroglucan, were examined in comparison with HPAM
on rheological behaviors, shearing resistance, long-term thermal stability,
and core flooding test. It was found that all of these three polysaccharides
were less sensitive to salinity and shearing time, while HPAM showed
a monotonous decrease in viscosity with increasing monovalent cations
and shearing history. After 90 days of aging at 85 °C and 10.1
× 10
4
mg·L
–1
of total dissolved
solids with 1.0 × 10
3
mg·L
–1
of Ca
2+
, the viscosity of diutan gum and scleroglucan
solutions nearly remained unchanged; on the contrary, the viscosity
of xanthan gum and HPAM solutions drops massively. Core flooding tests
at 85 °C with the same initial viscosity demonstrated that all
polymers showed good transportation in porous media, and 16, 13, and
11% of oil recovery were obtained by diutan gum, scleroglucan, and
xanthan gum, respectively, while only 10% was obtained from HPAM.
These comparative results may underpin the potential of diutan gum
and scleroglucan to be used in the EOR process in HTHS oil reservoirs.