可循环微泡沫钻井液流变性研究

Rheological Properties of Recycled Micro-Foam Drilling Fluids

采用线性回归分析方法对微泡沫钻井液的流变数据进行分析,优选出微泡沫钻井液的最佳流变模式为幂律模式τ=Kγn;研究并讨论了气体含量、压力和温度对其流变性的影响。结果表明,当泡沫体积分数大于24%时,微泡沫钻井液的高剪切应力随泡沫含量的增加而显著增大,而低剪切应力无明显变化。压力对微泡沫钻井液流变性的影响小于温度的影响。微泡沫钻井液具有较好的高温稳定性(100～150℃),随温度的升高未出现明显增稠或减稠现象。对各温度下的流变数据进行线性回归,得到不同温度下微泡沫钻井液的本构方程,线性相关系数均大于0.99。并由此得到微泡沫钻井液的流性指数n和稠度系数K与温度T的相关表达式:n=5.2584×10-9T4-2.0122×10-6T3+2.8151×10-4T2-1.6739×10-2T+0.8298,(R2=0.9982);K=-1.0769×10-8T4+4.7940×10-6T3-8.2658×10-4T2+5.8472×10-2T-0.1180,(R2=0.9998)。

The rheological data of micro-foam drilling fluids was analyzed by linear regression method and the optimum rheological model was power-law model τ= Kγn. The effects of air content, pressure and temperature on the rheological properties of micro-foam drilling fluids were investigated and discussed. The results showed that the stress at high shear rate increased dramatically with increasing volume fraction of foam when the volume fraction of foam was larger than 24%. However, the stress at low shear rate did not change significantly. The effect of pressure was smaller than that of temperature. The micro-foam drilling fluids had good stability at high temperature （100--150℃） , and no thickening and thinning phenomena were observed. The constitutive equations of tested liquids at different temperature were obtained by linear regression and the linear correlation coefficients were all more than 0.99. Based on the equations, the variations of liquidity index n and consistency coefficient K with temperature were established：n=5.2584×10^-9 T4-2.0122×10^-6T3＋2.8151×10^-4 T2-6739×10^-2 T＋0.8298,（R2=0.9982）;K=1.0769×10^-8 T4 ＋4.7940×10^-6 T3-8.2658×10^-4 T2＋5.8472×10^-2 T-0.1180,（R2=0.9998）.