Barite sag is a challenging phenomenon encountered in deep drilling with barite-weighted fluids and associated with fluid stability. It can take place in vertical and directional wells, whether in dynamic or static conditions. In this study, an anti-sagging urea-based additive was evaluated to enhance fluid stability and prevent solids sag in water-based fluids to be used in drilling, completion, and workover operations. A barite-weighted drilling fluid, with a density of 15 ppg, was used with the main drilling fluid additives. The ratio of the urea-based additive was varied in the range 0.25–3.0 vol.% of the total base fluid. The impact of this anti-sagging agent on the sag tendency was evaluated at 250 °F using vertical and inclined sag tests. The optimum concentration of the anti-sagging agent was determined for both vertical and inclined wells. The effect of the urea-additive on the drilling fluid rheology was investigated at low and high temperatures (80 °F and 250 °F). Furthermore, the impact of the urea-additive on the filtration performance of the drilling fluid was studied at 250 °F. Adding the urea-additive to the drilling fluid improved the stability of the drilling fluid, as indicated by a reduction in the sag factor. The optimum concentration of this additive was found to be 0.5–1.0 vol.% of the base fluid. This concentration was enough to prevent barite sag in both vertical and inclined conditions at 250 °F, with a sag factor of around 0.5. For the optimum concentration, the yield point and gel strength (after 10 s) were improved by around 50% and 45%, respectively, while both the plastic viscosity and gel strength (after 10 min) were maintained at the desired levels. Moreover, the anti-sagging agent has no impact on drilling fluid density, pH, or filtration performance.

中文翻译：

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用尿素基添加剂防止水基钻井液中的重晶石下垂

重晶石下垂是在使用重晶石加权流体进行深钻时遇到的一种具有挑战性的现象，并且与流体稳定性有关。它可以在垂直和定向井中进行，无论是在动态还是静态条件下。在这项研究中，对一种抗流挂的尿素基添加剂进行了评估，以增强流体稳定性并防止用于钻井、完井和修井作业的水基流体中的固体下垂。密度为 15 ppg 的重晶石加重钻井液与主要钻井液添加剂一起使用。尿素基添加剂的比例在总基液的 0.25-3.0 vol.% 范围内变化。这种抗流挂剂对流挂趋势的影响在 250 °F 下使用垂直和倾斜流挂测试进行评估。确定了直井和斜井的抗流挂剂的最佳浓度。在低温和高温（80°F 和 250°F）下研究了尿素添加剂对钻井液流变学的影响。此外，研究了尿素添加剂在 250 °F 下对钻井液过滤性能的影响。向钻井液中加入尿素添加剂提高了钻井液的稳定性，这表现为下垂系数的降低。发现该添加剂的最佳浓度为基液的 0.5-1.0 vol.%。该浓度足以防止重晶石在 250 °F 的垂直和倾斜条件下下垂，下垂系数约为 0.5。对于最佳浓度，屈服点和凝胶强度（10 秒后）分别提高了约 50% 和 45%，而塑性粘度和凝胶强度（10 分钟后）均保持在所需水平。而且，