Abstract

A biodegradable polymer drilling mud was prepared using Guinea corn starch pre- gelatinized in the absence of a solvent. The filtration and rheological properties of the mud were studied at 25 to 200°C temperature range and 0.01 to 0.05 g/mL concentration of starch using filter loss and viscomertric methods, respectively.  Experimental results showed that the new mud has better filtration control behavior and thermal stability at all the temperatures than widely used mud prepared with hydroxy propyl- modified starch. The mud displayed thermal degradation at 200°C. The values of flow index were found to be less than 1.0, showing non – Newtonian and Pseudoplastic flow behavior of the mud. Shear stress and yield stress increased with increase in concentration. Viscosity decreased with increasing shear rate, showing shear thinning behavior of the mud. The polymer mud obeyed Henri Darcy and API models for static filtration as well as Power law and Herschel–Bulkley models for fluid rheology. The new mud is purer and more suitable for drilling operation in environmentally sensitive areas than the widely used mud.

Key words: Biodegradable polymer, drilling mud, filtration, rheology, starch.