钻井液旋转粘度测试中双圆筒力矩分析

Analysis of drilling fluid rotational viscosity tests subjected to double cylinder moments

摘要:

流体的粘度能够直接反映不同流体的特性，其测量对于鉴定流体质量及确定其使用方向具有十分重要的意义。在钻探工作中钻井液粘度的变化会影响润滑油功能的实现，以粘度作为钻井液选用的依据，对钻井液粘度的测量就显得尤为重要。然而对于传统的旋转式粘度仪，由于内筒下表面所产生的附加力矩也同时作用在弹簧上，因此计算出液体作用在整个内筒上的摩擦力矩偏大，且底部平底面上各点的速度梯度及剪切应力均不相同，问题较为复杂。本文在传统的旋转式圆筒粘度计结构的基础上，对计算原理进行了改进补充，并通过采用有限元软件分析双圆柱绕流的流动特性，仿真结果与理论分析相一致，验证了推导公式的合理性。应用于钻井液在完整地层中的流动特性，可为进一步研究钻井液在破碎地层中的剪切应力提供基础，为预防孔内事故提供支撑。

关键词:钻井液;旋转粘度仪;粘度测量;有限元;数值分析

Abstract:

The viscosity of fluids can directly reflect the characteristics of different fluids， and its measurement is of great significance in identifying the quality of fluids and determining their direction of use. For example， the change of drilling fluid viscosity will affect the realization of lubricating oil function， and the viscosity parameter as a basis for the selection of the drilling fluid is particularly critical for the measurement of the viscosity of the drilling fluid. However， in the traditional rotary viscometer， the friction moment of the liquid acting on the whole inner cylinder is calculated to be large because the additional moment generated in the lower plane of the inner cylinder also acts on the spring at the same time， and the velocity gradient and shear stress at each point on the bottom flat surface are different， which makes the problem more complicated. In this paper， based on the traditional rotating cylinder viscometer structure， the calculation principle is improved and supplemented， and by using finite element software to analyze the flow characteristics of the double cylindrical winding flow， the simulation results are consistent with the theoretical analysis， which verifies the reasonableness of the derived formula. Applied to the flow characteristics of drilling fluid in intact formation， it can provide a basis for further research on the shear stress of drilling fluid in fractured formation， and provide support for the prevention of in-hole accidents.

Key words:drilling fluid;rotational viscometer;viscosity measurement;finite element;numerical analysis