Psyllium husk performance in drilling fluid at elevated temperature and pressure conditions

Abstract

High performance water-based drilling fluid alternatives that meet performance objectives with minimal environmental impact must continually be developed. Drilling fluid performance is dependent on fluid characteristics, and among those most critical are viscosity and filtration. One avenue to improve drilling fluid performance is through enhancement by use of potent, water-soluble natural polymers. Psyllium husk powder is an environmentally friendly natural polymer derived from ground-up surfaces of psyllium seeds (Plantago ovata). When in contact with water, psyllium husk powder forms a gel-like, extraordinarily viscous substance at very low concentrations. It was previously shown that pure psyllium husk is an excellent viscosity and filtration agent for water-based drilling fluid under standard conditions. Psyllium husk can also be used as a clay-extender to enhance viscosity and filtration performance of bentonite mud; however, further laboratory testing of this performance enhancement under elevated temperatures and pressures is required. Extensive laboratory experiments were therefore conducted to test husk performance in bentonite mud under such conditions. An electronic rheometer and a temperature and pressure adjustable API filter press were used to evaluate viscoelastic and filtration mud characteristics respectively. Concentrations of 0.05–0.4% husk with 5% bentonite were tested at 25−120°C under 1500 psi. An optimal husk concentration of 0.1% was determined, increasing bentonite viscosity and yield point by up to 46.9% and 68.1% respectively. Filtrate loss rate and filtration cake thickness were reduced by up to 25.8% and 35.3% respectively. The optimal concentration was useable up to 70°C (~2800 m) before deflocculating was required.