The research of pipeline lifting model in horizontal directional drilling

In recent years, Horizontal Directional Drilling has been the first choice in trenchless engineering of pipeline crossing for its strong environmental adaptability, high efficiency and low cost. In order to reduce the resistance force and avoid pipeline damage in construction, the angle formed by the pipeline axis and hole axis should be lessened when the pipeline is lifted to a height. However, the stress status of the pipeline is very complex during the lifting process. Hence the research of pipeline lifting process is great importance for pipeline safety. In this paper, a finite element model is established to uncover the stress variety law of pipeline during lifting process. And then its reliability was verified by the experimental method. At last, the results of engineering experiment show that the finite element model which is credible can be used to reveal the stress variety law of the pipeline during the lifting process

THE MECHANICAL ANALYSIS OF PIPELINE LIFTING DURING THE HORIZONTAL DIRECTIONAL CROSSING

If the hoisting position is bad during the engineering application of the lifting pipe,which may bring the serious influence when the pipe smoothly enters the grave,even happen stuck pipe and tube flat accidents. Through the mechanical analysis of the pipe lifting,themathematical model about lifting point position and the grave angle was established,which on the basis of reasonable assumptions. The location of the lifting point 2 affects on the size of the grave angle more than lifting point 1by mathematical model analysis. And then compared with the calculated value of mathematical model and the value of test measurement,the relative error of theoretical calculation value and experimental value that is about 5. 8% was discovered.Therefore,the mathematical model can be used to guide the actual construction

The Effects of Boundary Conditions and Friction on the Helical Buckling of Coiled Tubing in an Inclined Wellbore

<div><p>Analytical buckling models are important for down-hole operations to ensure the structural integrity of the drill string. A literature survey shows that most published analytical buckling models do not address the effects of inclination angle, boundary conditions or friction. The objective of this paper is to study the effects of boundary conditions, friction and angular inclination on the helical buckling of coiled tubing in an inclined wellbore. In this paper, a new theoretical model is established to describe the buckling behavior of coiled tubing. The buckling equations are derived by applying the principles of virtual work and minimum potential energy. The proper solution for the post-buckling configuration is determined based on geometric and natural boundary conditions. The effects of angular inclination and boundary conditions on the helical buckling of coiled tubing are considered. Many significant conclusions are obtained from this study. When the dimensionless length of the coiled tubing is greater than 40, the effects of the boundary conditions can be ignored. The critical load required for helical buckling increases as the angle of inclination and the friction coefficient increase. The post-buckling behavior of coiled tubing in different configurations and for different axial loads is determined using the proposed analytical method. Practical examples are provided that illustrate the influence of the angular inclination on the axial force. The rate of change of the axial force decreases with increasing angular inclination. Moreover, the total axial friction also decreases with an increasing inclination angle. These results will help researchers to better understand helical buckling in coiled tubing. Using this knowledge, measures can be taken to prevent buckling in coiled tubing during down-hole operations.</p></div

The effects of friction coefficient on the dimensionless critical load for helical buckling with different boundary conditions.

<p>The effects of friction coefficient on the dimensionless critical load for helical buckling with different boundary conditions.</p

The effect of friction coefficient <i>f</i>_<i>2</i> on the critical load for helical buckling <i>F</i>_<i>crh</i>.

<p>The effect of friction coefficient <i>f</i>_<i>2</i> on the critical load for helical buckling <i>F</i>_<i>crh</i>.</p

The relationship between the dimensionless axial force of the coiled tubing and the number of helical turns with the different friction coefficient.

<p>The relationship between the dimensionless axial force of the coiled tubing and the number of helical turns with the different friction coefficient.</p

Coiled tubing in an inclined wellbore (side view).

<p>Coiled tubing in an inclined wellbore (side view).</p

The combined effects of friction coefficient <i>f</i>_<i>2</i> and inclination angle <i>α</i> on the critical load for helical buckling <i>F</i>_<i>crh</i>.

<p>The combined effects of friction coefficient <i>f</i>_<i>2</i> and inclination angle <i>α</i> on the critical load for helical buckling <i>F</i>_<i>crh</i>.</p

The relationship between the dimensionless critical load for helical buckling and the dimensionless length with the different friction coefficient.

<p>The relationship between the dimensionless critical load for helical buckling and the dimensionless length with the different friction coefficient.</p

Variation in the critical load for helical buckling <i>F</i>_<i>crh</i> as a function of angle of inclination <i>α</i>.

<p>Variation in the critical load for helical buckling <i>F</i>_<i>crh</i> as a function of angle of inclination <i>α</i>.</p