Is There a Viscoelastic Effect of Low-MW HPAM Polymers on Residual Oil Mobilization in Low-Permeability Rocks at a Darcy Velocity of 0.2 ft/Day?

Abstract

High-molecular-weight (MW) polymer solutions with significant viscoelasticity have been reported to positively influence residual oil saturation (Sor) reduction at high pressure gradients and/ or high fluxes. The lower the permeability, the lower the acceptable MW for transportable polymers and, therefore, the lower the viscoelastic effects in porous media. The objective of this paper is to answer the following question: how does a polymer's viscoelasticity influence Sor reduction in low-permeability formations? Initially, two low-MW polymer systems are formulated by varying the concentration, and sequential core flooding is performed with a 35 mD rock sample by injecting the viscous polymer first followed by a relatively elastic polymer at a low Darcy velocity of 0.2 ft/day. Results reveal that viscous 6000 ppm HPAM 3130 injection corresponds to a 55.9% recovery with an injection pressure of ∼80 psi. Interestingly, the secondary injection of relatively elastic 4500 ppm HPAM 3230 further increases the recovery to 58.8%, thereby resulting in an incremental recovery of 2.9% at an injection pressure of ∼60 psi. This incremental oil recovery due to the elastic polymer can solely be attributed to residual oil mobilization that is well-swept during the preceding viscous polymer injection at a relatively higher pressure. Although Sor reduction is observed with the elastic polymer at a relatively low pressure of 60 psi, 60 psi generated during 0.2 ft/day propagation in low-permeability rocks is still in the high range. This work provides experimental evidence for residual oil mobilization in low-permeability rocks with a low-MW high-concentration elastic polymer at 0.2 ft/day.

Enhancing Oil Recovery in Low-Permeability Reservoirs Using a Low-Molecular Weight Amphiphilic Polymer

“…For a given permeability and a pore throat size, a threshold MW exists, above which HPAM molecules exhibit poor injectivity. The MW of the HPAM used in polymer flooding is usually higher than 12 million daltons, which makes the use of HPAM applicable in reservoirs with an average permeability greater than 100 mD [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. When it comes to low-permeability reservoirs with an average permeability lower than 50 mD, an HPAM with medium and high WM is not applicable.…”

Chemical Enhanced Oil Recovery and Viscose Flooding into Sandstone Reservoirs Using a Natural Polymer Extracted from Sucrose‐Rich Waste by Bacterial Activity

“…This, in turn, helps mitigate issues such as high water cut and poor sweep efficiency in water injection processes. [6][7][8][9][10][11] DOI: 10.1002/ente. 202400564 In this research, it was attempted to describe in vitro the efficiency of a natural polymer synthesized from sugarcane waste by bacteria for application in enhanced crude oil recovery.…”