Friction between wellbore/casing and drill string causes excessive torque.
In particular, shallower formations are affected more by drill string impacts than deeper ones.
The rotation of a compression-buckling rotation drill string can increase the frictional force between the drill string and borehole wall, induce lateral vibration and whirl of the drill string, generate borehole wall instability and drill string damage, and even cause a drilling failure.
The results indicates that the contact force between wellbore and drill string is relatively large and helical buckling of drill string can be caused without the lubrication and damping effects of drilling fluid in gas drilling.
Drilling fluid channel is actually a multi-layer cylindrical waveguide, which consists of drill string drilling fluid, drill string, and annulus drilling fluid.
Downhole air injection technology involves parasitic pipe, concentric pipe, drill string, and coiled tubing drilling.
After rock softening, the drill string′s critical speed decreases, whereas the wellbore rock fragmentation volume increases; compared to a radial impact by the drill string, the drill string′s rotation speed plays only a secondary role in rock failure.
The numerical simulation model of drill string with positive displacement motor is established by considering the bit-rock interaction, the rock failure behavior, the drill string-borehole interaction and the drill string structural.
Given the currently inadequate understanding about drill string dynamic characteristics in gas drilling of horizontal wells, a theoretical model of drill string dynamics is established in this paper.
While drilling, a fluid is pumped through the drill string and the drill bit, and is returning through the annulus between the drilled well and the drill string.
The nonlinear buckling analysis of drill string in a rigid well is presented in this paper.
