非牛顿钻井液剪切速率计算公式的推导及验证

Derivation and Verification of Shear Equation for non-Newtonian Drilling Fluid

范式旋转黏度计由于具有使用简单、便于携带等特点,而被广泛运用于现场和室内实验中。为了能够较准确地计算范式旋转黏度计剪切非牛顿钻井液时的剪切速率,在理论模型的基础上推导出了新的剪切速率求解公式,并通过室内实验进行了验证。实验验证结果表明,剪切非牛顿钻井液时,相对于目前常用的剪切速率计算公式的求解结果,采用新推导的计算公式求得的剪切速率与采用高准确度、高精度的安东帕流变仪测得的实验结果更加接近,准确度更高;而且被测液体的非牛顿性越强,2种计算方式得到的结果差值越大。

The Fann viscometer is widely used in laboratory researches and filed applications because of its simplicity in operation and portability. To accurately calculate the shear rate of non-Newtonian fluids with Fann viscometer, a new equation was developed on the basis of theoretical modeling, and was verified through laboratory experiment. The new equation, compared with currently used equations, gives more accurate shear rates, more close to the shear rates obtained on the Anton Paar rheometer. It is also observed that the smaller the flow index number, n,(which means more non-Newtonian) of drilling fluids, the bigger the difference between the calculated shear rates with the new equation and the currently used equations.