Stress Analysis on Drilling String Vibration in Gas Drilling

Using the finite element method, attempting to solve the serious drilling tools failure in gas drilling, this paper modelled the transient response of string vibration, and worked out the distribution regularity of the transient stress at two different drilling states: gas and mud drilling. Research shows that the stress fluctuation in gas drilling is greater than that in mud drilling; the alternate stress under such two drilling conditions has the same value relationship as those of stress fluctuation. The string vibration level is gradually increasing from the head to the bottom of the well Thus it is easier to cause the drill string fatigue failure. Such mechanism analysis, which explains the cause of string tools failure, provides guidance in drilling string design optimization.