The Research On Dynamic Buckling Of Tubular String Of Vertical Well Under Impacted Bottom Conditions

As a non-renewable strategic resource,oil plays an important role in the national economy.With the rapid development of the national economy,the demand for oil and gas is increasing and the existing oil and gas supply is in short supply.As a result,the exploitation of oil and gas gradually develops from inland to ocean,shallow to deep and ultra-deep,and the difficulty is gradually increasing.In the process of exploitation,petroleum engineers focus on how to improve oil and gas recovery,with little attention to safety issues.However,in drilling and production operation,occasionally the drill string,casing string,tubing string,rod string may break,or the brake doesn’t work,or the operation error occurred,causing the tubular string to slide down the wellbore and impact the bottom of the well.Under this condition,the tubular string is subject to transient dynamic impact loads,which may cause dynamic sinusoidal buckling,helical buckling,and even plastic deformation and fracture of the tubular string,causing significant economic losses and even catastrophic consequences for oil and gas exploitation.The impact dynamic problem of tubular string is not only a typical example in drilling and production,but also a typical example in elastic mechanics.Through the study of the dynamic buckling of the tubular string impinging the bottom of well,not only the drilling and production level can be improved,but also the development of elastic mechanics can be promoted,which has important engineering and academic value.In drilling and production operation,the tubular string plays an important role in petroleum engineering as an important tool for drilling,and the problem of tubular string buckling has always been a hot research topic in the petroleum engineering field.Firstly,the research status of scholars in the tubular string buckling of domestic and foreign scholars is investigated.The test bench was designed and built,and the experiment was carried out to simulate the buckling phenomenon of the tubular string under static axial load,and the buckling configuration of the tubular string was judged.Secondly,the theoretical aspects of the buckling configuration of tubular string under static axial load are deduced in vertical well,and the solution is compared with the experimental results.Thirdly,the test bench for simulating the tubular string to impact the bottom of the well was designed and built.Experiments were carried out.The characteristics of the influence parameters(tubular string length,diameter,and different impact velocity)of the dynamic buckling of the tubular string under vertical wellbore conditions are studied through experiments.The results show that when the impact force between the tubular string and the bottom of the well is small,the tubular string does not buckle,and the phenomenon of multiple impact-rebound occurs,and eventually it is still;when the impact force between the tubular string and the bottom of the well is large,the tubular string will buckle;plane buckling or helical buckling that does not contact the wellbore occurs;when the impact force increases to a certain value,helical buckling occurs,and even plastic deformation and fracture may occur.When the tubular string strikes the bottom of the well,buckling occurs at a certain distance from the lower end of the string,then buckling develops to the upper end of the string.At this time,buckling deformation of the lower end of the string slows down.During the rebound process,the tubular string sticks to the wall of the well and stays still after repeated impact-rebound.Finally,the theoretical derivation of dynamic buckling of tubular string under the condition of vertical borehole impact bottom hole is carried out.