Experimental Study On Buckling Behavior Of Tubular String Constrained By Horizontal Wellbore

Buckling behavior of downhole tubular string has a significant impact on many aspects of well engineering,such as drilling & completion,fracturing,well intervention and so on.Therefore,theoretical study on the buckling behavior of downhole tubular string is of great significance to the production practice.The theoretical study on buckling behavior of downhole tubular string can be carried out in both theoretical and experimental aspects.So far,there is a relatively complete theoretical system in study of downhole tubular string buckling.However,experimental study is limited by the experimental conditions and considerations of the unity of the experimental conditions,leading to the lacking of verifications on experimental results.Especially,the experimental study of the joint effect is very few.In this paper,based on the previous theoretical system and experimental situation,previous experiments are improved to simulate the horizontal wellbore string buckling.Comparisons are made between the experimental value and the theoretical value of loading on tubular string under different constraints,the influence of the number and size of different connectors on critical values of loading on tubular string is studied,the influence of the horizontal borehole friction and torque on buckling of tubular string is analyzed experimentally,and the effect of buckling with or without connectors on the axial force transfer efficiency is compared.Theories about influence of friction and torque on critical values of buckling and axial force transfer efficiency are verified.It is found that the increase of the number of connectors in a certain range will decrease the critical value of the sinusoidal buckling and increase the critical value of the spiral buckling;the increase of the joint size will increase the buckling critical value of the string;axial force transfer efficiency increases with tubular connector effect.These innovative theories are of reference value to theoretical analysis and engineering application.