Impact of Rotation During Installation on the Structural Performance of Slotted Liners in Thermally Stimulated Wells

Abstract

Summary Slotted liner is a sand–control technology used for completion of thermal wells. During installation, liners are subjected to tensile and compressive loads generated by string weight, wellbore drag, and bending when run through curved wellbores. Additionally, torque might be applied to “break” friction, when needed, to reduce axial drag and extend reach. These conditions lead to combined loading of liners with simultaneous axial, bending, and torsional loads. Combined loading that exceeds the elastic capacity of the liner during installation can alter the structural capacity of the liner and reduce its ability to withstand subsequent operational loads. In particular, permanent deformation of liner struts during installation could create weak zones that trigger localization of deformations and liner failure under thermal–service loading conditions. Further, the presence of residual torque (from installation) can trigger and exacerbate the tendency of the liner struts to buckle. Previously published works described slotted–liner installation limits and thermal operating limits separately. This paper examines the impact that rotation (during installation) can have on the subsequent thermal–service capacity and sand–control performance of a slotted liner. Specifically, the relationships between both plastic twist and residual torque from installation loads and the critical strain capacity and slot–width changes of a slotted liner under constrained thermal expansion were studied. Results demonstrated that a slotted liner can tolerate some plastic twist (during installation) without a significant impact on slot width or thermal–service performance. However, large amounts of plastic twist or residual torque from installation can bias the liner to fail in torsional buckling during thermal service. Slotted–liner tolerance, to both the plastic twist applied during installation and the residual torque remaining after installation, varies with liner configuration. Small amounts of plastic twist (0.5°/m) imposed on a high–density 60–slots–per–column (spc) liner resulted in a reduction in thermal–service capacity. In contrast, a low–density 35–spc liner with substantial imposed plastic twist (4°/m) demonstrated negligible changes in performance. Residual torque has a greater potential to impact liner performance, and its effect is less sensitive to the slotting density. Both the high–density 60–spc liner and the low–density 35–spc liner showed significant incremental slot–width changes during thermal service resulting from 5 kN·m of residual torque. The findings of this work provided the basis for a proposed method to select appropriate engineering limits for the torque that can be applied safely to a slotted liner during running and for recommendations to reduce the potential for residual torque following installation.