用于冻土区天然气水合物钻探的聚合物钻井液低温流变响应

陆域天然气水合物（以下简称水合物）主要赋存于高原冻土区，为保证顺利钻探，要求钻井液既能够有效抑制水合物分解、 维持其相态平衡，又能在低温环境下具有良好的流变性能。为此，以新研制的低失水抗低温聚合物钻井液配方为研究对象，对其在 低温条件下的流变性能进行了测试，并利用回归分析法和最小二乘法对试验数据进行计算与分析。结果表明：①赫谢尔-巴尔克莱 模式是描述该钻井液体系低温流变性能的最佳模式；②应用该模式计算得到了低温条件下钻井液流变性能参数，其变化规律表现出 随着温度降低，钻井液动切力呈近似波动变化，钻井液的稠度系数和流性指数均大致呈线性增长的趋势，但增长幅度较小。结论认为： 所建立的钻井液表观黏度低温响应数学模型拟合精度高，可准确预测井内钻井液在低温下的流变性能。

Low-temperature rheological response characteristics of the polymer drilling fluid developed for permafrost gas hydrate exploration

Terrestrial natural gas hydrate resources are widely distributed in plateau permafrost areas, where pioneer drilling, however, will be frustrated by the extremely low temperature conditions causing a negative impact on the rheological properties of drilling fluids. In view of this, with the newly developed water-based polymer drilling fluid with low filtration as a research object, its low-temperature rheological properties were tested and the experimental data were analyzed by use of regression analysis and the least square methods. The following findings were obtained. First, the Herschel-Bulkley model is the best one to characterize the low-temperature rheological performances of this drilling fluid system. Second, according to the rheological parameters calculated by this model under ultra-low temperatures, the experimental results show that along with the decreasing temperatures, the dynamic shear force of the drilling fluid presents approximate fluctuations while its consistency factor and the rheological properties shows the trend of small linear growth. On this basis, a responding mathematical model with a high fitting accuracy was established to predict the apparent viscosity of the drilling fluid under low temperatures, which may lay a foundation for the forthcoming natural gas hydrate exploration in permafrost areas.