A Study On The Technique Of Using Swirling Jet For Lost Circulation Control & Wellbore Stability Enhancement While Drilling

Circulation loss and its induced wellbore instability have always been a big issue for drilling.Many scholars and engineers have done research on the solutions while drilling,but till now,almost all of them have just been focusing on drilling fluids and additives.This study throws a new light upon this issue by handling it from the physical mechanical aspect,i.e.using a drilling tool to improve the circulation loss control and enhance the wellbore stability.Firstly,I pointed out the inappropriate explanations previously proposed by some scholars for the mechanism of using swirling jet for lost circulation control & wellbore stability enhancement while drilling,and put forward my new explanations.Then a stress analysis based on linear-elastic rock was made to probe into the relationship between wellbore collapsing pressure,fracturing pressure and the fractures on the wellbore so that a qualitative theoretic explanation for the mechanism of the technique could be given.And from the explanation,I found the scope of application for this technique.All the results in this stage made a basic contribution to the theory of the technique.Secondly,based on the related theories,I gave a detailed process of designing the swirling-jet lost-circulation-control drilling tool and the effects of different structural parameters were concluded for the convenience of better improving the tool structure in future application.At last,the prototypes were manufactured and deployed for field tests with considerably good effects achieved which verified the feasibility and economical value of the technique of using rotatory jet for lost circulation control & wellbore stability enhancement while drilling...