1. 东北石油大学石油工程学院;
2. 中国石油化工股份有限公司石油工程技术研究院

A magnetic torque optimization method for a hydraulic-magnetic coupling-drive cuttings cleaning tool
Sun Xiaofeng1, Hu Qiaobo1, Yan Lipeng2, Chen Ye1, Zhang Kebo1
1. School of Petroleum Engineering, Northeast Petroleum University, Daqing, Heilongjiang 163318, China;
2. Sinopec Petroleum Engineering Research Institute, Beijing 100101, China
Abstract

In the process of well drilling, cuttings carrying is difficult in the horizontal section, and cuttings beds tend to form easily. In view of this, a hydraulic-magnetic coupling-drive cuttings cleaning tool is newly developed, but its magnetic torque transmission mechanism, optimum magnetic circuit structure and magnet layout are rarely researched. In this paper, the influence laws of magnetic circuit structure and permanent magnet dimension on the magnetic torque were analyzed by using finite-element numerical simulation method. And the following research results were obtained on the basis of numerical simulation and experimental study. First, the transmission efficiency of magnetic torque can be enhanced by increasing the magnetic flux density in the air gap, decreasing the magnetic circuit reluctance or increasing the magnetostatic energy. Second, the magnetic torque increases first and then decreases as the number of pole-pair increases. And it reaches the maximum value when the number of pole-pair is 12. Third, based on the coupling of the magnet volume under two constraints, i.e., the coverage area of permanent magnet on the tool's effective cross section and the magnet thickness, the thickness of permanent magnet is 8.4 mm. And the magnetic torque on the unit volume of magnet reaches the maximum value when the coverage area of permanent magnet on the tool’s effective cross section is 71%. Fourth, the absolute error between the experimental result and the numerical simulation result is less than 17%. It is indicated that the numerical simulation model can satisfy the required engineering calculation accuracy. In conclusion, the numerical simulation model established in this paper is rational and can be used as a technical method for optimizing the structure of this newly-developed tool.

Keyword: Horizontal drilling; Cuttings; Cleaning tool; Hydraulic-magnetic coupling; Permanent magnet; Magnetic torque; Magnetic flux density; Numerical optimization
0 引言

1 工作原理

 Figure Option 图1 液力— 磁耦合传动岩屑清洁工具结构示意图

 Figure Option 图2 磁传动剖面示意图

2 磁传动扭矩有限元分析

2.1 磁场参数计算方程

 Figure Option 图3 磁传动机构横截面图

$\bar{\Omega}=\Omega \bigcup \Gamma_{1} \bigcup \Gamma_{2} \bigcup \Gamma_{3} \bigcup L \bigcup L_{1}$

。根据Maxwell电磁场方程理论知在Ω 中有：

$\nabla B=0$ （1）

$\nabla H=0$ （2）

$B=\nabla A$ （3）

2.3 磁扭矩数值模拟

2.3.1 前处理

2.3.2 边界条件

2.3.3 网格划分与求解

3 各参数对气隙磁场、磁扭矩的影响规律分析
3.1 相对磁轴偏角对磁扭矩的影响规律

 Figure Option 图6 不同磁偶对数下磁扭矩与相对磁轴偏角关系曲线图

3.2 磁偶数量对磁扭矩的影响规律

 Figure Option 图7 不同工具有效断面永磁铁覆盖面积下磁偶对数与最大磁扭矩关系曲线图

3.3 工具有效断面永磁铁覆盖面积对磁扭矩的影响规律

 Figure Option 图8 不同磁偶对数下工具有效断面永磁铁覆盖面积与磁扭矩关系曲线图

 Figure Option 图9 12磁偶模型不同工具有效断面永磁铁覆盖面积磁通量分布云图

3.4 永磁铁厚度对磁扭矩的影响规律

 Figure Option 图10 不同工具有效断面永磁铁覆盖面积下永磁铁厚度与磁扭矩关系曲线图

 Figure Option 图11 永磁铁覆盖面积与厚度两参数对磁扭矩影响的等高线图

4 数值模拟模型计算精度的实验验证

5 结论

1）磁扭矩与相对磁轴偏角呈正弦周期性变化, 在相对磁轴偏角为π /PP为磁偶对数）时取得磁扭矩最大值。

2）磁扭矩随磁偶对数的增加呈先增大后减小的趋势, 在磁铁体积用量相同时, 磁偶对数选择12对, 磁扭矩最大。

3）工具磁偶对数确定后, 有效断面永磁铁覆盖面积对磁扭矩影响规律曲线近似抛物线, 存在极值点。

4）随着永磁铁厚度的增加, 磁扭矩不断增大, 但增长速率逐渐减小, 相同磁铁厚度下, 工具有效断面永磁铁覆盖面积越高, 磁扭矩增长率越大。

5）液力— 磁耦合传动岩屑清洁工具与常规钻杆配套使用, 建议磁偶对数选择为12对, 气隙厚度大于钻杆壁厚, 选择为9.5~10 mm。当永磁铁厚度为8.4 mm, 工具有效断面永磁铁覆盖面积为71%时, 单位体积磁铁产生最高磁扭矩, 实现经济最优化。

The authors have declared that no competing interests exist.