MECHANICAL DEGRADATION OF POLYACRYLAMIDE IN HIGH-SHEAR CAPILLARY FLOW EXPERIMENTS

Open Access
Author:
Pawlik, Taylor Kristen
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Manish Kumar, Thesis Supervisor
  • Ali Borhan, Honors Advisor
Keywords:
  • Hydraulic Fracturing
  • High Shear
  • Mechanical Degradation
  • Polyacrylamide
  • Power Law
  • High Pressure
  • Capillary Flow
Abstract:
During high volume hydraulic fracturing (HVHF), high rates of pumping through narrow fractures might create a high shear environment that could lead to mechanical degradation of high molecular weight polyacrylamide (PAM) used as a drag reducer. This degradation could increase the likelihood of releasing the monomer acrylamide, a neurotoxin and potential carcinogen, into the returning wastewater. The objective of this study was to determine the power law index (n) and consistency factor (K) of PAM under extremely high shear rates using high pressure (i.e. ~10,000 psi) flow through an abrupt contraction (i.e. narrow capillary), which was then used to examine the degree of mechanical degradation. The responding pressure drop values of fluid through two different diameter capillaries were recorded under constant flow rate controlled by high-pressure precision pumps. Linearized pressure and velocity parameters were used to determine n and K. Size exclusion chromatography was used to determine molecular weight change due to mechanical degradation. The power law index was determined to be 0.955 and the consistency factor was determined to be 5.06x10-3. The molecular weight of the polymer was relatively unchanged below a shear rate of 1.0x10-6 s-1, and decreased exponentially as shear rate increased. The distribution of molecular weight narrowed as shear rate increased, indicating that the majority of mechanical degradation occurred at the midpoint of the polymer chain.