钻井液黄原胶胶液的流变特性研究

RHEOLOGICAL PROPERTIES OF XANTHAN GUM SOLUTION IN DRILLING FLUID

以钻井液黄原胶水溶胶液为研究对象，研究了浓度、pH值、温度、剪切速率等因素对低浓度黄原胶水溶胶液流变性的影响，以及黄原胶水溶胶液体系的流变模型。研究表明，在一定剪切速率下，黄原胶水溶胶液浓度越大，黏度越高，非牛顿性越强；温度升高会使体系黏度降低，当温度恢复到初始温度时，黏度恢复到初始黏度的70％～80％；pH值在6～7时，黏度最大；剪切速率为1～100s^-1时，黏度急剧下降，剪切速率为100～500s^-1时，黏度下降缓慢；体系流变模型符合Herschel～Bulkley方程；体系剪切稀释性明显，触变性较小。在石油天然气钻井工程中，低浓度（0．1％～0．7％）的XC水溶胶液就能满足钻井、完井液增黏、降滤失、改善流型等方面的需要。

In this paper, the rheological properties of low-concentration water solution of Xanthan gum are evaluated at different concentrations, different pH values, temperatures and shear rates, and the rheologic model is set up. The results show that at a given shear rate, the higher concentration induces higher viscosity and stronger nonnewtonianism; the higher temperature will bring the lower viscosity, the viscosity will get back to 70%-80% of the original when the temperature returns to the original; the viscosity reaches the highest when pH is kept within 6-7; and when the shear rate is 1-100 s-1 ,the viscosity will decrease very sharply in contrast to slow viscosity decrease when the shear rate is within 100-500 s-1. The rheological model complies with the Herschel-Bulkley Equation, and the system has prominent shear-thinning effects, with indistinctive thixotro-py. In petroleum drilling, the low-concentration (0. 1%-0. 7%, mass fraction) XC solution can meet the needs of viscosity picking-up, filtration reduction, and flow pattern improvement.