Mechanical stability of high‐molecular‐weight polyacrylamides and an (acrylamido tert‐butyl sulfonic acid)–acrylamide copolymer used in enhanced oil recovery

Abstract

High-molecular-weight partially hydrolyzed and sulfonated polyacrylamides are widely used in enhanced oil recovery (EOR). Nonionic polyacrylamide and polyacrylamide-based microgels are also used in water shut-off treatments for gas and oil wells. A comparative study of the mechanical degradation for three linear polyacrylamides and a microgel is presented. Mechanical degradation is quantified from the loss of the viscosity of the polymer solution as it passes through a stainless steel capillary with a length of 10 cm and an internal diameter of 125 mm. The critical shear rate above which degradation increases exponentially was found to depend on the chemical structure of the polymer, molecular weight, and electrolyte strength. The nonionic polyacrylamide shows higher degradation and lower critical shear rate compared with a sulfonated polyacrylamide with similar molecular weight. Moreover, the nonionic polyacrylamide with a higher molecular weight results in lower mechanical degradation. The higher mechanical stability of the sulfonated polymer is attributed to the higher rigidity of its molecules in solution. On the other hand, the ability of the highmolecular-weight polymers to form transient, flow-induced microgels boost their mechanical stability. This ability increases with the increase in the molecular weight of the polymer. Indeed, the microgel solution used in this study demonstrates exceptional mechanical stability. In general, mechanical stability of linear polymers used in chemical enhanced oil recovery can be enhanced by tailoring a polymer that has large side groups similar to the sulfonated polyacrylamide. Also, polyacrylamide-based microgels can be applied if high mechanical stability is required.

Water Soluble Polymers

“…The amphiphilic graft copolymer was found to be more resistant to shear degradation and fluid recirculation than pure PAAM. Other derivatives, including copolymers of N-alkyl-and N-arylalkylacrylamides with AM [80], (acrylamido tert-butyl sulfonic acid)-acrylamide copolymer [81], polyacrylamide-grafted chitosan [82], and guar-g-polyacrylamide [83], etc., are also being studied as drag reducing agents.…”

Polymeric Drift Control Adjuvants for Agricultural Spraying

“…Other observed trends include the preferential scission of polymers at the midpoint of the chain and an increase in degradation rate with larger solvent viscosity and higher chain flexibility. [102,107,108] Although this phenomenon is widely reported in the literature as 'shear degradation', it is generally believed that simple laminar shear flow is unable to break polymer chains and that extensional or turbulent flow (which itself contains an extensional element) is required for chain scission to occur. [98,102,109] In general, there are two types of elongational flow which are separated by whether or not the residence time (tr) is greater than the polymer chain relaxation time (λ).…”

“…Additionally, the charged groups on polyelectrolytes reduce the flexibility of the polymer chain, which may also contribute to the improved stability. [108] At polymer concentrations above the critical overlap concentration, the electrostatic interactions are increasingly shielded through an increase in concentration of counterions. A similar effect is achieved through the addition of salts into the polymer solution.…”

Preparation and probing of the steady shear flow and viscoelastic properties of weakly crosslinked hydrogels based on sulfonated polyacrylamide for oil recovery applications

“…Partially hydrolyzed polyacrylamide (HPAM) and sulfonated polyacrylamide (SPA) are well known water soluble and commercially available polymers whose solutions and gels are employed in many com mercial applications, especially for enhanced oil recovery and control of the excess water production through profile modification and blocking the paths with high permeability to water [3][4][5][6][7][8][9][10][11][12][13][14].…”