不同流变模式钻井液环空层流压耗通用算法

General method of calculating annular laminar pressure drop of drilling fluids with different rheological models

针对钻井工程中常用环空层流压耗计算方法精度低、不适用于复杂流变模式的问题,提出了适用于不同流变模式钻井液的环空层流压耗通用算法,与传统算法进行了对比,并采用已发表文献中实验数据进行了验证。基于环空槽流模型,将圆管流量方程推广应用于环空中推导出环空流量方程,利用环空流量方程和流体流变方程建立环空流量与管壁剪切应力的关系式,再由已知流量求得管壁剪切应力,进而求得环空压耗。通过与传统算法的对比分析发现:提出的通用算法适用于所有流变模式的钻井液环空层流,普适性好、建模过程简单、计算精度高。基于已发表文献中实验数据的算法验证结果表明:不论是在低排量还是在高排量条件下,采用通用算法求得的不同流变模式环空压耗与实测结果都能较好地吻合,弥补了传统算法的误差。

Traditional annular laminar flow analysis method applied in drilling engineering has poor accuracy and does not apply to complicated rheological models. A general method of calculating annular laminar pressure drop of drilling fluids with different rheological models was proposed, compared with traditional method, and verified using experiment data in published articles. Based on annular slot flow model, the pipe flow equation was popularized in annular and an annular flow equation was established, and the relationship between annular flow and shear stress at pipe wall was established by combining annular flow equation and fluid＇s rheological equation. If annular flow is given, shear stress at pipe wall can be got, and then the annular pressure drop is also available. Compared with traditional methods, the general method is adapt to any rheological model of annular laminar flow, and has good universality, simple modeling process and high accuracy. The calculation results based on experiment data in published articles show： no matter the flow rate is high or low, the results of the general method match the measured results well, which makes up the error of traditional method.