Modelagem axissimétrica de conexões de colunas de perfuração submetidas à tração e torque de instalação

Abstract

Oil and gas are often located at great depths, requiring extensive drill strings joined by robust connections. These connections are subjected to intense and complex loads, making them prone to mechanical weak points, particularly in the threads of rotary-shouldered connections. A fundamental aspect of connection performance is the make-up torque, which ensures proper tightening between components. Additionally, the robustness of these elements, often made of steel, necessitates studies to assess their operational limits, particularly concerning the maximum load the connection can withstand under operating conditions without the cross-sectional area experiencing maximum stress exceeding the steel's yield strength. In this context, the present study proposes using the Finite Element Method (FEM) to analyze the stress distribution in a connection subjected to make-up torque preloading and axial tensile load. The methodology is divided into three main stages: pre-processing, processing, and post-processing. In the first stage, the threaded connection is modeled according to the standards of the API (American Petroleum Institute), assigning material properties, applying initial interference fit, defining boundary conditions and loads, and generating the mesh in ABAQUS®. The second stage involves processing the data in the software, enabling access to output variables and their graphical visualization. In the third stage, the data are interpreted, and the Stress Concentration Factor (SCF) is calculated to identify the location of the highest stress concentration levels in the connection. The results demonstrate that modeling in ABAQUS® allows for a detailed visualization of the problem and the distribution of von Mises equivalent stresses along the axisymmetric section of the connection. It is observed that the highest stress concentration levels occur at the root of the first engaged thread of the pin, aligning with findings from reference studies in the literature. Regarding the response of the steel used, it is possible to determine the maximum stress the connection can develop without exceeding the yield strength, establishing an important design criterion.