关键词: 定向钻井, 地层力, 各向异性指数, 井眼轨迹, 造斜, 方位

Abstract: The formation force is an important factor affecting the bit trajectory iar di rectional drilling.Thus it is necessary to quantitatively analyze the formation force in order to predict and control the bit trajectory,In this paper some new concepts are presented.including the drilling anisotropy index c.af the bit and total anisotropy cutting index between the bit and rock.The authors givea new consideration of the characteristics of the bit,formation anisotropy dip angle and strike,weight on bit,tilt angle of the bit,area or volume breakage,etc.A general model to calculate the fomation deviating force for either area or volume breaking of rock and its corresponding shapes in simplified conditions are established.In this paper,the formation forces affecting the changes in the inclination angle and the azimuth angle are denoted by F_α and F_φ respectively.Equations determining the magnitudes of F_α and F_φ are derived by means of WOB-cone method.The critical dip angle equation is also given.The authors give a quantitative explanation of the walking tendency of the bit with this equation.Verification tests show good agreement between theoretical analysis and practical use.