On Improving Water-Based Drilling Mud Swelling Control Using Modified Poly(Vinyl Alcohol)s.

Area of Science:

• Petroleum Engineering
• Materials Science
• Polymer Chemistry

Background:

• Wellbore instability in high-temperature, high-pressure (HT/HP) drilling is a critical challenge.
• Clay swelling and drilling fluid loss exacerbate wellbore instability.
• Polyvinyl alcohol (PVOH) derivatives are explored as additives to mitigate these issues.

Purpose of the Study:

• To evaluate the effectiveness of nonionic and cationic modified polyvinyl alcohols (PVOH) in water-based muds (WBM) for HT/HP drilling.
• To assess the impact of PVOH on mud rheology, specific gravity, and filtration characteristics at elevated temperatures.
• To determine the adsorption behavior of PVOH polymers on clay particles.

Main Methods:

• Preparation of nonionic and cationic PVOH polymers.
• Introduction of PVOH into WBM at varying concentrations (0.08, 0.28, 0.49 wt.%).
• Experimental analysis of specific gravity, mud rheology, and filtration at temperatures of 25, 55, and 85 °C.
• Thermogravimetry analysis (TGA) for thermal stability assessment.

Main Results:

• Mud specific gravity and rheology decreased monotonically with increasing temperature.
• Nonionic PVOH enhanced mud filtration by up to 34.7%, significantly more than cationic PVOH.
• Nonionic polymers exhibited higher adsorption onto clay particles (118.9 mg/g) compared to cationic polymers (84.51 mg/g).

Conclusions:

• Modified PVOH polymers, particularly nonionic types, show promise in improving drilling fluid performance under HT/HP conditions.
• Nonionic PVOH effectively reduces fluid loss and enhances mud cake quality.
• The study demonstrates the potential of tailored polymer additives for stabilizing wellbores in challenging drilling environments.