Hydrolysis and thermal stability of partially hydrolyzed polyacrylamide in high‐salinity environments

Abstract

Partially hydrolyzed polyacrylamide (HPAM) is the water-soluble polymer most often used in flooding applications in the petroleum industry. However, in aqueous solutions at high temperatures, HPAM undergoes hydrolysis of the lateral amide groups, and the presence of salts in the solution can lead to precipitation of this polymer. Therefore, a method was developed to monitor the thermal stability of HPAM solutions in different saline environments and varying temperatures. The proposed test method involved measurements of intrinsic viscosity as a function of time and determination of the degree of hydrolysis of the HPAM by elemental analysis. The results obtained indicated that the presence of divalent cations (Ca +2 and Mg +2 ) negatively influenced the intrinsic viscosity of the solutions and in some systems led to precocious precipitation of the polymer in environments with higher concentrations of these cations. The hydrolysis reaction of the amide groups to the acrylate groups of the HPAM chain was significantly affected by rising temperature: at 50 C, hydrolysis occurred, but not as significantly as at 70, 85, 90, and 95 C. Hydrolysis up to 84% was observed for solutions processed at 90 C. The results also indicated limits of hardness for the brine at some temperatures: 1353 ppm for 95 C and 2867 ppm for 70 C. For brine containing 13,610 ppm or more of divalent cations, hydrolysis and precipitation of the polymer were not observed at 50 C.

Evaluation of Polymeric Materials for Chemical Enhanced Oil Recovery

“…Since the stoichiometric proportions of the individual elements are known, calculating the molar fraction of each comonomer is relatively straightforward. This approach is more widely used in recent EOR literature [29,61,67].…”

“…Since oxygen contamination can severely impact the thermal degradation of polymeric materials, many researchers choose to work under anaerobic or partially anaerobic (low O 2 ) conditions (see, for example, [11,31,59,67,99,[101][102][103][104][105]). This approach ensures that the effects of other factors (like brine composition) are not overshadowed by the effects of residual oxygen.…”

“…Each variable's effects was evaluated in terms of hydrolysis and/or viscosity retention; degradation was determined to be more severe when more hydrolysis had occurred and/or the viscosity retention was lowered [11]. Similar studies (with unique polymeric materials) have been pursued by many other researchers [31,59,67,99,[101][102][103][104], each with slight alterations in technique.…”

Treatment of partially hydrolyzed polyacrylamide by mixed bacteria isolated from wastewater

“…The average molecular weight of HPAM used in this work was about 8 × 10. 6 The medium used for enrichment was LB medium containing 3 g/L yeast extract, 10 g/L tryptone, 5 g/L NaCl, pH 7.2-7.4. Mineral salts medium supplemented HPAM (MSMP) used as the sole carbon source and nitrogen source for domestication and screening contained…”

High‐viscoelastic graft modified chitosan hydrophobic association polymer for enhanced oil recovery

“…[5][6][7] However, HPAM shows limited thermal stability and cannot withstand high salinity, which limits the field application of tertiary oil recovery. [8][9][10] In this context, there is a large demand for stable new polymers in the harsh reservoir environment.…”