Vacuum Insulated Tubing Design and Performance Evaluation for Deepwater Completions

Abstract

fax 01-972-952-9435. AbstractThis paper presents a methodology and a software program for mechanical design of vacuum insulated tubing (VIT) strings. It also presents findings of a technical and experimental evaluation of a VIT candidate product under conditions typical for ChevronTexaco's Tahiti project in the Gulf of Mexico.The design-and-evaluation methodology consisted of an initial feasibility study of VIT thermal properties and service loading conditions, a closed-form solution of the VIT stressstrain state under combined loading, a parametric finite element analysis (FEA) with simulation of interactions within VIT end connections, and a full-scale test of a VIT specimen under cyclic thermal and mechanical loads that were anticipated in field service.A complex experimental set-up was developed to apply the required combined loads to a full-length VIT joint. The test specimen was instrumented with strain gauges to measure the VIT deformation in a fully submerged environment.The paper presents examples of data acquired in all phases of this design-and-evaluation program. The results were used for assessment of structural integrity, sealability, and thermal insulation performance of the VIT candidate product. The experimental data agreed well with analytical and numerical predictions. The paper also shows how these results were further used to develop a VIT string design program, which calculated stresses and safety factors in function of VIT geometry and loading conditions. The conclusions of this paper include recommendations for VIT design and performance verification. Following these recommendations should result in higher reliability and more cost effective wells in completion programs utilizing VIT for deepwater applications.

Transient Fluid and Heat Flow Modeling in Coupled Wellbore/Reservoir Systems

“…Tahiti resulted in this well having several sealed casing annuli and the possibility that annular pressure buildup could burst or collapse casing strings. To mitigate annular pressure buildup potential, the Project Team designed a vacuum insulated subsea production tubing string for use in producers (Nowinka et al 2005). During the flow test, a subsurface mandrel with a memory-only gauge was placed at the base of the vacuum insulated portion of the tubing string (9,600 ft MD) to acquire pressure and temperature data, which is useful to calibrate and verify wellbore flow models.…”

Transient Fluid and Heat Flow Modeling in Coupled Wellbore/Reservoir Systems

“…Operational contingencies overcome while drilling the original discovery well at Tahiti resulted in this well having several sealed casing annuli and the possibility that annular pressure buildup could burst or collapse casing strings. To mitigate annular pressure buildup potential, the Project Team designed a vacuum insulated subsea production tubing string for use in producers (Nowinka et al 2005). During the flow test, a subsurface mandrel with a memory-only gauge was placed at the base of the vacuum insulated portion of the tubing string (9,600 ft MD) to acquire pressure and temperature data, which is useful to calibrate and verify wellbore flow models.…”