Feasibility Study of Tannin-Lignosulfonate Drilling Fluid System for Drilling Geothermal Prospect

Abstract

Deflocculant is added into drilling fluid to disperse the flocculated clay that may lead to the loss of rheological properties at a higher temperature. Drilling into a well at the temperature above 150 ˚C, drilling fluid components or additives is susceptible to degrade, thus affect the performance of drilling fluid. This study aims to evaluate the potential of tannin-lignosulfonate as a deflocculant in drilling fluid for drilling a geothermal well. Tannin-lignosulfonate was synthesized by a crosslinking of 4 different weight ratios of Acacia spp. tannin and lignosulfonate. The functional group of synthesized tannin-lignosulfonate was confirmed using Fourier transform infrared (FTIR) spectrum over a range of 4000 and 400 cm-1 wavenumber. Subsequently, the decomposition rate assessment by thermogravimetric analysis (TGA) provided an evidence of thermal stability tannin-lignosulfonate. Gel strength of tannin-lignosulfonate drilling fluid was measured using Fann-viscometer at room temperature for 7 different drilling fluids sample. The thermal stability of tannin-lignosulfonate was identified at 294 ˚C and remains more than 60% of weight at that temperature. It was found that the 10 seconds and 10 minutes gel strength was reduced with the addition of deflocculant in each sample.