Delving Deeper into Foundation Slurry Rheology-Paper

Paper

Pdf Summary

The paper examines why partially hydrolyzed polyacrylamide (PHPA) foundation slurries often show sharply lower Marsh Funnel (MF) readings after standing, even when they have received little additional mixing.<br /><br />Tests found that ultra-high-molecular-weight PHPA slurries could lose about 30% of their initial MF value after 24 hours and roughly half after 48 hours. Fann rheology changed much less over the same period. The author argues that this difference is mainly due not to polymer-chain breakage, but to long polymer chains gradually hydrating and disentangling. In fresh slurry, weakly associated chains form rope-like structures that impede flow through the Marsh Funnel opening and inflate its reading. As the structures disperse over time and with shear, MF values fall. Higher-molecular-weight polymers may entangle more and show larger declines, while still producing greater viscosity per unit dosage after hydration.<br /><br />The Marsh Funnel is therefore best treated as a comparative “difference detector,” not a complete measure of slurry rheology. Fann or Brookfield measurements provide more information about how the fluid behaves.<br /><br />The paper also describes how lost-circulation materials (LCMs) can affect MF readings by obstructing the funnel opening. Polymer entanglement may also interfere with LCM dispersion, potentially influencing their performance in the ground.<br /><br />Soda ash can help sequester calcium in hard or brackish water, but in low-hardness water it adds salt, which can hinder polymer hydration and reduce viscosity. Its use should depend on water quality; sodium hydroxide may be more effective where dissolved magnesium is high, though it is highly caustic.<br /><br />Overall, slurry age, polymer molecular weight, mixing, water chemistry, and LCM handling all affect MF results, so readings should be interpreted with these factors in mind.

Keywords

partially hydrolyzed polyacrylamide

PHPA

Marsh Funnel

rheology

polymer hydration

polymer entanglement

foundation slurry

lost-circulation materials

soda ash

water chemistry