LATERAL VIBRATION OF DRILL STEM IN DEEP WELL

This paper discuss the process of creation,transmit and vanish of lateral vibration in bottom of drillstem.Analysing shows that lateral vibrations create and exist in bottom of drill stem only.The causes producing lateral vibration relate directly with buckling of BHA,dynamic unstable and collision between well wall and drillstem.The vibration energy caused by interaction of bit and formations is consumed by spiral buckling stem.Vibration above neutral point of stem caused by eddy movement and collision and inhibited by drilling fluid damp during transmitting upward.The axial force effect vibration frequency and wave transmitting.Neutral point is dangerous but is not energy trap point.