The evaluation of micronized barite as a weighting material for completing HPHT wells

Barite is one of the most common weighting materials for drilling and completion fluids. Its good properties (high density, less environmental impact, and low production cost) outperform the other weighting materials and make it a good candidate for drilling and completing oil and gas wells. However, some problems were encountered in the industry while using solid particles to increase fluid density, solids invasion which causes formation damage and permeability reduction in the vicinity of the wellbore, and the tendency of these solid particles to settle therefore, the loss of well control is likely. Moreover, an erosion to the surface facilities will result when these solid particles are produced. This study aims to investigate the effect of barite particle size on barite removal and completion fluids stability and how reducing barite particle size will help in resolving barite sag tendency and mitigating its effect. In this study, different samples of barite with different particle sizes were prepared using sieve analysis. Ball milling was used to reduce barite particle size to few microns. zeta potential and sag test were performed to evaluate the stability of micronized barite. Solubility test and high pressure high temperature filter press were used to study the effect of reducing barite particle size on barite removal. Solubility tests showed a good enhancement in barite removal as the particle size was reduced, with a difference of around 11 g/L (20 wt.%) between the largest and the micronized size of barite. HPHT Filtration test results confirmed the solubility results with 5 wt.% enhancement in filter cake removal efficiency. Micronized barite showed a moderate stability with zeta potential measurements for a pH range greater than 8, while sag test showed insignificant enhancement in fluid stability as barite particle size was reduced to the micronized size.