The effect of barite particle mass fraction and of particle size distribution on the settling and sag potential in oil-based drilling fluid samples is investigated for four fluids with densities of 1.43, 1.55, and 1.60 specific gravity (S.G). The fourth fluid sample, with density 1.60 S.G., had sieved barite particles of sizes less than 40 $\mathit{\mu }\mathit{m}$. The settling potential in a liquid column under static condition has been characterized using light scattering measurements whereas sag potential in a sheared liquid column has been characterized under a dynamic condition using a rotating cylinder rheometer to produce rotational shear. Extensive rheological characterization of the drilling fluid samples is carried out where the Herschel-Bulkley fluid parameters were defined. We observed that the rate of particle settling under static condition was faster in the fluid sample of S.G = 1.43 having the least barite concentration. There was longer suspension of particles within the fluid sample of S.G = 1.60. Fluid sample with the sieved barite recorded weak destabilization of particles within the middle and bottom column of the sample after 7 days. The viscosity and viscoelastic-linear elasticity also increased with increasing barite concentration which contributed to lower dynamic sag for all shear rates. Time-dependent oscillatory shear measurements provide new insights on the structural character of drilling fluids to predict barite sag tendencies during the fluid design phase.

对于四种密度分别为1.43、1.55和1.60比重（SG）的流体，研究了重晶石颗粒质量分数和粒度分布对油基钻井液样品中沉降和下陷电位的影响。第四个流体样品的密度为1.60 SG，筛分的重晶石颗粒尺寸小于40$\mathit{\mu }\mathit{米}$。静态条件下液柱中的沉降势已通过光散射测量进行了表征，而剪切液柱中的液流势已在动态条件下通过使用旋转圆柱流变仪产生旋转剪切力进行了表征。在定义了Herschel-Bulkley流体参数的地方，对钻井液样品进行了广泛的流变学表征。我们观察到在重晶石浓度最低的SG = 1.43的流体样品中，静态条件下的颗粒沉降速度更快。SG = 1.60的流体样品中颗粒的悬浮时间更长。筛分重晶石的流体样品在7天后记录到样品中部和底部圆柱体中的颗粒微弱失稳。粘度和粘弹性-线性弹性也随着重晶石浓度的增加而增加，这有助于降低所有剪切速率下的动态下垂。随时间变化的振荡剪切测量提供了有关钻井液结构特征的新见解，以预测在流体设计阶段的重晶石下陷趋势。