Study on weighting agent of ultra-high density water-based drilling fluid

The conventional weighting admixture of ultra-high density water-based drilling fluid may lead to viscosity effects, which means that the drilling fluid could lose its flow property due to high viscosity. In this paper the properties of barite optimized by using surface activation and particle classification. First the optimum dosage of surfactant (RAB) was determined after experiments of electric potential effect and rhelogy behavior; furthermore, on the basis of classical accumulation theory and plenty of laboratory experiments, the particle size ranges under different modulus and the optimum particle classification were calculated by using the distribution equation of Dinger-Funk. An industrial specific barite was produced by adjusting and optimizing production process and then was applied into several deep wells with ultra-high pressure in Sichuan area. Finally, the ultra-high density water based drilling fluid (with the density of greater than or equal to 2.65 g/cm3) is successfully prepared on site. The applied results show that the ultra-high density water-based drilling fluid with special barite has characteristics of weighted high density, easy controlled rhelogy behavior, and anti-salt water invasion resistant. It can satisfy the actual requirement of practical drilling operation, and thus worth popularizing.