HPHT Fatigue Resistant Wellhead System Design First Use
Authors: Nguyen K. , Grohmann A. , Lu W. , Mercan B. 
Published: April 2024

The Anchor Project is a deepwater, high pressure project with a shut-in tubing pressure (SITP) greater than 15,000 psi and flowing tubing temperature up to 275°F. The Anchor field is located in the Green Canyon, offshore Gulf of Mexico (GOM), approximately 140 miles off the Louisiana coast in approximately 5,000 feet of water. The Anchor subsea development consists of seven wells, with two production drill centers tied back to a floating production unit (FPU). To deliver Anchor, the project team embarked on a world class technology development program delivered within the execution of a deepwater project. This project used the Dril-Quip 20,000 (20k) psi rated BB IIe subsea wellhead system with DXe mandrel profile and gasket, and a Badger casing connector. This paper describes the fatigue assessment and fatigue resistance design of the 20k rated BB IIe wellhead system and the fatigue monitoring of the deployed wellhead system.

A fit-for-purpose wellhead system for high pressure, high temperature (HPHT) applications was developed with enhanced performance in structural and fatigue loading. The wellhead system has been fully verified using advanced analysis tools and validated with full-scale load testing to static loads and the anticipated fatigue load spectrum. Additionally, in-situ wellhead fatigue monitoring has been performed during the drilling of the first well to verify its structural integrity for the operating conditions. The wellhead system design adheres to the latest industry standards.

The full wellhead system was designed to accommodate extreme environments and loads in HPHT applications. The system was designed by analysis and used 3D models to accurately capture the load distribution and interaction of the complex components in the assembly. Further refined analysis was used to optimize the fatigue performance in areas with structural discontinuities and stress risers. A full-scale wellhead system test was performed in normal, extreme, and survival load capacity conditions. For all analyzed cases, the system performed as designed and showed no signs of damage. The full-scale wellhead system, including the wellhead connector, was fatigue tested and demonstrated superior fatigue performance. In addition, the entire system was reviewed by an independent third party (I3P) and was approved by the Bureau of Safety and Environmental Enforcement (BSEE) for Anchor application. The fit-for-purpose system was successfully installed in the first Anchor development well without any lost time. A wellhead load monitoring scheme was also implemented to track the actual wellhead fatigue life consumption during drilling operations. The wellhead loads are planned to be monitored during future drilling, completion, intervention, and plug and abandonment operations.

The BB-IIe's high fatigue performance coupled with high structural capacities, metal sealing performance, full-scale testing, and value-added economics provide a unique wellhead system solution for the industry. This paper will cover details about the design, analysis, full-scale structural and fatigue testing, installation, and other safety and performance features.

For clarity, the following terms are used throughout this paper. High Pressure High Temperature (HPHT) refers to equipment rated to pressures greater than 15,000 psi and / or temperatures equal to or greater than 350°F. Anchor is a high pressure project under the HPHT category. 20K refers to the Anchor project's technology development and qualification program.