Bentonite suspension have been widely used as drilling fluid in drilling engineerings. In this work, a modified thixotropic loop test was conducted on 6 wt% bentonite suspensions with 4 solution salinities, to investigate the influence of salinity on rheological behaviors of Na-bentonite suspensions. Most of flow curves were well fitted with Herschel-Bulkley model except first upward curves, where stress overshoot appeared in the initial stage. It was found that the yield stress and flow index decreased with increasing salinity. The suspensions present shear thinning behavior in the first upward curves but shear thickening or Bingham behavior in the second loops. Besides, at 20 and 14 °C, a notable thixotropic type transition was observed from positive to negative when the second shear loop was applied to the suspensions in case of low salinity. Both the change of flow type and thixotropy mentioned before may be attributed to the further structural evolution resulting from the long-time shearing at low salinities. However, this change was suppressed at 4 g/L due to the effect of high salinity on particle association mode. The test at 7 °C showed interesting results that the twice upward flow curves presented the stress overshoot and the twice loops performed a positive thixotropic behavior, not as same as the cases of the other temperatures. It indicates the structural evolution during shear process may be affected at low enough temperatures.

膨润土悬浮液在钻井工程中被广泛用作钻井液。在这项工作中，对具有 4 种溶液盐度的 6 wt% 膨润土悬浮液进行了改进的触变回路试验，以研究盐度对 Na-膨润土悬浮液流变行为的影响。大多数流动曲线与 Herschel-Bulkley 模型拟合良好，但第一条上升曲线在初始阶段出现应力超调。发现屈服应力和流动指数随着盐度的增加而降低。悬浮液在第一个向上曲线中呈现剪切变稀行为，但在第二个循环中呈现剪切增稠或宾汉行为。此外，在 20 和 14 °C 下，当在低盐度的情况下将第二个剪切环应用于悬浮液时，观察到显着的触变型从正到负的转变。前面提到的流动类型和触变性的变化都可能归因于低盐度下长时间剪切导致的进一步结构演变。然而，由于高盐度对颗粒结合模式的影响，这种变化在 4 g/L 时被抑制。在 7 °C 下的测试显示了有趣的结果，两次向上流动曲线呈现应力超调，两次循环执行正触变行为，与其他温度的情况不同。这表明在足够低的温度下，剪切过程中的结构演变可能会受到影响。由于高盐度对颗粒结合模式的影响，这种变化在 4 g/L 时被抑制。在 7 °C 下的测试显示了有趣的结果，两次向上流动曲线呈现应力超调，两次循环执行正触变行为，与其他温度的情况不同。这表明在足够低的温度下，剪切过程中的结构演变可能会受到影响。由于高盐度对颗粒结合模式的影响，这种变化在 4 g/L 时被抑制。在 7 °C 下的测试显示了有趣的结果，两次向上流动曲线呈现应力超调，两次循环执行正触变行为，与其他温度的情况不同。这表明在足够低的温度下，剪切过程中的结构演变可能会受到影响。