马氏漏斗黏度计测定钻井流体流变参数新方法的建立

A New Method of Measuring Rheological Properties of Drilling Fluids with Marsh Funnel Viscometer

目前使用马氏漏斗黏度计作为流变仪使用,所得到的数学模型计算过程繁琐、精度不足,无法满足现场测定钻井流体流变参数的需求。笔者针对牛顿型与非牛顿型钻井流体,优化了流量系数、壁面剪切速率、壁面剪切应力及流变曲线的数学模型,得到了测定牛顿黏度、表观黏度、塑性黏度以及动切力的新数学模型。结果表明,模型下矿物油、合成油、燃料油、绒囊冲洗液及甲酸盐钻井液的流变曲线与HAAKE MARSⅢ流变仪所测得的流变曲线之间存在很强的正相关性,相似度很高;模型下5种钻井流体的牛顿黏度、表观黏度、塑性黏度以及动切力的测量值与ZNN-6旋转黏度计的测量值之间的误差分别为1.40%、4.29%、2.78%与10.13%;说明了,建立的新方法可准确、简便地求得钻井流体的流变参数,计算准确度与ZNN-6旋转黏度计相符,可满足现场钻井流体流变学设计的需求。

The Marsh funnel viscometer is now used as a rheometer to measure the rheology of drilling fluids. The mathematical model obtained from the use of Marsh funnel viscometer, which has tedious calculation process and poor precision, is unable to satisfy the needs of measuring the rheological properties of the drilling fluids at rig site. This paper discusses the optimization of the mathematical models of flow coefficient, shear rate and shear stress prevailing at the borehole wall, and rheological curve for Newtonian and nonNewtonian fluids. Based on the study a new mathematical model for calculating the Newtonian viscosity, apparent viscosity, plastic viscosity and yield point was obtained. It was found that there is a strong positive correlation between the rheological curves obtained from the model for mineral oils, synthetic oil, fuel oil, follicle flushing fluid and formate drilling fluid, and the rheological curves of these fluids obtained on HAAKE MARS Model Ⅲ rheometer. The errors between the Newtonian viscosity, apparent viscosity, plastic viscosity and yield point of five fluids obtained with the new model and those obtained with ZNN-6 rotational viscometer are 1.40%, 4.29%, 2.78% and 10.13%, respectively, indicating that the new model as a simple way can be used to reliably measure the rheological properties of drilling fluids and gives results that satisfy the needs of rheological design at the rig site.