Computational Analysis On Casing Stability And Thread Connection Strength And Its Experimental Research

With the development of super deep well, oil well contained gases, and thermalproduction well, etc., and oil mining conditions getting increasingly severe, the ordinarycasing which are in line with the criteria of API but cannot meet the demand of oilproduction completely, thereby research institutions and manufacturers carried out theresearch and development of casing one after another. The overall performance research ofcasing usually can be divided into three broad categories of problems: one is resistance tocollapsing performance of the casing, namely how to improve the collapsing strength ofcasing; the second is the problem of connection strength, that is how to enhance thebearing capacity of the casing joint; the third problem is sealing performance of casingjoint which means how to increase the reliability of the seal. The core performance ofcasing is its collapsing-resistance, which is vital to maintain the stability of casing. Thestrength of screw joint is not only the weakest link of the whole casing but also animportant performance. This article will have an in-depth study of collapsing-resistanceperformance and screw joint strength of casing.First of all, this paper analyzed the model of collapsing experiments and the mainfactors that affecting the collapsing strength of casing, then a finite element model wasdeveloped to simulate the collapsing process of casing with detailed description of themechanical model and model parameters. Take casing P110Φ177.8×9.19as the researchobject, the article explained the collapsing process of casing in details using simulationsoftware and obtained the load-displacement curve of casing during the collapsing process,thus the anti-collapsing pressure of this casing was gained. By comparing the simulatingcalculation results with the experimental results, we can see that the former tallied wellwith the latter, which verified the accuracy and feasibility of using the proposed finiteelement model to simulate and calculate.Next, the author wrote APDL command flow on the basis of the finite elementmodel obtained in the previous part, and analysed the anti-collapsing performance of steeltube by applying the secondary development of ANSYS. Then ANSYS simulating and computing system was developed using Delphi programming language, which realized afriendly interface, easy operations and accurate calculations, and achieved the capsulationcalling of ANSYS, interactive input of parameters, the anti-collapsing pressure, cloudpicture and direct view of animation in the post-processing result; Combined withpractical examples, the feasibility of the program was verified.At the same time, this paper researched the coupling casing P110Φ139.7x7.72API,and analysed the thread connection strength of the casing. The finite element software-ABAQUS was applied to simulate the performance of the casing. A two-dimensitionalaxisymmetrical finite element model was built based on certain assumptions of the finiteelement model. According to the finite element model, the mechanical properties of thescrewed joints working in the5000-meter-deep sea were simulated and computed usingABAQUS, which validated the accuracy and feasibility of the model. Finally, the slipmechanism of buttress thread was further studied; thus, an optimization scheme toimprove the resistance to slip performance of the screwed joints was put forward.