Experimental investigation of lateral contact force in horizontal and directional wells

Vita.This study investigated the post-buckling behavior of tubular goods in horizontal and directional wells and determined lateral contact force. As the magnitude of the contact force increases, a helically buckled pipe can become lockedup making it almost impossible to drill further. Our equation for determining the magnitude of the contact force for a given axial force and radial clearance can help avoid lock-up conditions and costly failure of the tubular. Generally, the term lockup of tubulars refers to the state when the bit weight can not be further increased by slacking-off weight at the surface, or when the tubular can not be pushed further into the wellbore. At this point the hook load decreases to zero and it becomes impossible to drill further. We have directly measured lateral contact force alon- at least one- half pitch of the helically buckled rod or tubular constrained in a circular pipe. Physical measurements of this force under our test conditions differ significantly from-n the results of the currently accepted equation for estimating lateral contact force exerted by the helically buckled tubular on the hole wall. Our experli-nental studies led to the development of an experimentally verified equation for determining lateral contact force. Effects of wellbore curvature on buckling have also been studied and their implications with regards to lateral contact force are discussed. It was observed that wellbore curvature considerably delays the onset of critical and [ ] curved wellbores. Experimental results also indicate that friction between the tubular and the curved wellbore is always present, although its effects were not quantified