Research on weighting materials and rheological control technology for high-density drilling fluids

Abstract:

To address the challenges of high solid content and difficult rheological control in high-density drilling fluids for deep and ultra-deep well drilling， this study systematically investigates the fundamental properties of various weighting materials. The effects of density， particle size， and particle size distribution （PSD） on drilling fluid rheology were analyzed. Based on the dense packing theory， the particle size distribution of weighting agents was designed and validated through laboratory experiments. The results indicate that higher material density leads to a lower solid volume fraction required to achieve the target fluid density， thereby yielding better rheological properties. Smaller particle sizes and larger specific surface areas result in more significant viscosity effects， with fine particles smaller than 20 μm in barite powder causing a substantial increase in apparent viscosity. A drilling fluid with a density of 2.3 g/cm3， formulated using barite with an optimized PSD， exhibited a 19% reduction in plastic viscosity compared to the non-optimized sample， along with an increased yield point and significantly improved rheological properties. This study provides a physical control method based on particle size distribution optimization for high-density drilling fluids， demonstrating strong engineering application value.