为了更全面地考虑影响机械钻速的因素、提高预测机械钻速和井眼轨迹的准确性,深入研究了涉及钻头和地层相互作用的三维钻速方程。考虑钻头转速的影响,重新定义了钻头各向异性指数和地层各向异性指数;利用地层各向异性指数和钻头各向异性指数的定义以及坐标变换,建立了考虑钻头转速影响、钻头与地层相互作用的新三维钻速方程。利用新三维钻速方程,实例分析了钻头转速对机械钻速的影响,随着钻头转速的增加,井底平面Xd方向、Yd方向及井底法向Zd方向的机械钻速都随之提高,但井底3个方向的机械钻速随钻头转速增加而提高的幅度并不相同,井底法向Zd方向机械钻速的提高幅度要大于井底Xd和Yd方向机械钻速的提高幅度。研究表明,钻井过程中,利用新三维钻速模型可以预测钻头转速变化对机械钻速和井眼轨迹的影响,也可以通过调整钻头转速、钻头各向异性指数、钻头机械力等参数对井眼轨迹进行控制。
In order to fully consider the factors affecting the ROP and improve the accuracy of predicting the ROP and wellbore trajectory,the 3D ROP equation involving the interaction between bit and formation was studied.Considering the effect of rotary speed of the bit,the bit anisotropic index and the formation anisotropic index were redefined.Based on the definition of both anisotropic indexes and the coordinate transformation,a new 3DROP equation considering the rotary speed of bit and the bit-formation interaction was established.Using the new 3DROP equation,apractical case was taken to analyze the effect of rotary speed on ROP.It was found that all ROPs in Xddirection,Yddirection and normal Zddirection increased with the increase of rotary speed,but to different extents.ROP in normal Zd direction increased more than that in Xdand Yddirections.The results showed that the new model could be used to predict the change of ROP and wellbore trajectory with the change of rotary speed in drilling operations,and that the wellbore trajectory could be controlled by adjusting the rotary speed,bit anisotropic index,bit mechanical force and other parameters.