Abstract: Accurate prediction of the build angle rates and design of the assemblies of steerable-motor systems are the key techniques to achieve steering drilling.The bent-housing motor is relatively rigid,so the geometric method can be used to calculate the build angle rate of steerable motor.A type of correctional three-point geometry was proposed,in consideration of the position of bent-angles and the radial clearance between bottom stabilizer and borehole wall.The calculated results from the correctional three-point geometry are very close to the actual build angle rates.The presented formulae are simple,and the precisions in calculation are high.The calculated results of correctional three-point geometry are in good agreement with the results form the fine geometric method.The design method for steerable-motor assemblies using the geometric build angle rate was proposed,and the correlative formulae and some design examples were given.

Key words: drilling theory, steering drilling technology, horizontal drilling, steerable-motor assembly, mathematical model

摘要： 准确地预测和设计导向钻具的造斜率是实现导向钻井的关键技术之一。弯壳体导向钻具的刚性大、变形小,因此可采用几何法来计算造斜率。考虑到结构弯角位置以及稳定器与井壁间隙对钻具造斜率的影响,提出了修正的三点定圆法,使计算结果更接近于工程实际情况,且其计算公式十分简明,具有很高的计算精度,与精确的三点定圆数学方程得出的几何造斜率基本吻合。同时提出了利用几何造斜率设计导向钻具组合的方法,给出了相关的计算公式和一些设计实例。

关键词: 钻井理论, 导向钻井技术, 水平钻井, 导向钻具组合, 数学模型