Casing Design for Long Radius Horizontal Wells: Considering Buckling Effects

Abstract

Casing design for horizontal wells requires consideration of increased well angles and friction between the casing and the wellbore wall. These factors elevate the tensile load and reduce collapse resistance, necessitating the use of stronger casing materials. This study evaluates the casing design used in the EBO-Hz well and identifies inefficiencies in the current selection. The casing design evaluation, considering burst, collapse, and tension loads from prior drilling operations, demonstrates that lower-grade casing and connections can be effectively utilized for the EBO-Hz well. Additionally, this study analyzes casing buckling, which can occur if the casing lacks sufficient weight to withstand external and internal loads. Factors contributing to casing buckling include buoyant force, piston force, changes in drilling fluid density, and temperature variations. For this analysis, only the buoyant force is considered, as the casing has a uniform inner diameter, assumes no fluid settling, and no significant temperature variations. The focus is on the buoyant force during casing landing and cementing, which could lead to buckling at the bottom section. The results indicate that the 13-3/8” casing is liable to buckle and requires a 2000 lb slack-off load to prevent it. In contrast, the 9-5/8” casing has sufficient weight to avoid buckling, and the 7” liner does not exhibit any buckling tendencies. Furthermore, this study designs the configuration for setting the 7” liner, resulting in a configuration that includes 3181 ft of drill pipe (DP), 2251 ft of heavy-weight drill pipe (HWDP), and 1509 ft of 7” liner.