Numerical Analysis on the 3D Mechanical Behavior of Completion Tubing under Subsidence Loading

Abstract

For openhole completions in a weak sand formation, the failure of completion tubing frequently occurs under the loading from formation subsidence resulting from production. This paper investigates the integrity of completion tubing in this environment using the 3D finite element method (FEM). An elastoplastic analysis was performed on four sets of completion tubing using 3D FEM. A porous elastoplastic model was used to model the mechanical behavior of a weak sand formation. The interaction between the completion tubing and the sand formation was modeled with frictional contact constraints. The inclination angles of the completion tubing are set at 15°, 35°, 50°, and 75°. With a given geostress field and pressure depletion from production, the numerical results obtained with the 3D FEM model include subsidence of the sand formation, distribution of the equivalent plastic strain, and von Mises equivalent stress within the completion tubing and its deformed mesh. The principal conclusions include: 1) major loading factors affecting tubing failure are the axial pulling force and the bending moment or normal pressure applied on the external surface of the formation subsidence; 2) including an extendable tubing section can release the axial tensile stress caused by production-induced formation subsidence, and thus keep the tubing intact; 3) various scenarios have been checked for a safe pore pressure depletion value with a variation of tubing parameters values. This work presents a best practice for estimating the completion tubing integrity under subsidence loading by using a 3D FEM tool.

Tripability Analysis of Casing Strings in Directional Wells Using the Continuous Beam-Column and Buckling Theory

“…Due to the large size of the actual borehole, the establishment of a full-size three-dimensional finite element model of the borehole trajectory and casing string combination required not only a high amount of computational resources but also a long time to perform the calculations. It was believed that the mechanical behavior of a point in the structure would have no effect on the point in space beyond 15 m [29]. Therefore, the well section at 1210-1410 m was selected.…”