Presented by Nick Pacewicz, General Manager

Wednesday, July 15, 2020 | 3:00 PM GMT / 9:00 AM CDT

In this webinar, you will learn about how 2H Offshore and Chevron went about designing a custom subsea wellhead clamp. It will also cover the remedial actions that can be taken to extend the life of subsea wells showing signs of degradation or deviation from their as-built configuration, what to consider when designing components that must be installed subsea onto existing architecture, and what types of operational issues can be solved through design of bespoke equipment.

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Detailed Event Outline

The subsea wellhead acts as an interface between the subsurface oil and gas well and the well control equipment above, providing a critical role in maintaining well control and avoiding loss of hydrocarbons to the environment. Some older wells use non-rigid lock wellhead designs, where the wellhead housings are held in place using a lock ring, with some relative movement between the housings under load.

As these wellheads age, they can be prone to integrity issues. If the lock ring fails, the HP housing may become unseated, either from thermal well effects, or bending loads imparted by a connected riser system. This reduces both the wellhead’s strength and residual fatigue resistance.

Chevron have observed multiple instances of the HP housing unseating in their Captain B development, located in the Outer Moray Firth, UKCS. The phenomenon is believed to be caused by the thermal growth of the casing during hot injection operations. In some instances it has been found that the retainer ring is holding the HP housing within the LP housing, causing significant cyclic bending moments to occur in the weld immediately below the HP housing forging, increasing fatigue damage accumulation rates at this location. In others, the retainer ring has failed entirely and the HP housing has moved upwards.

This paper presents the process by which a custom clamp has been designed by Chevron in coordination with 2H Offshore, to facilitate repositioning of the HP housing relative to the LP housing by divers; the device is designed to exert a specified downwards force, calculated such that it will overcome the combined thermal and bending loads it will experience. The design is segmental to allow it to be installed by diver whilst the subsea tree remains in place.

Learning Outcomes

• Remedial actions that can be taken to extend the life of subsea wells showing signs of degradation or deviation from their as-built configuration
• What to consider when designing components that must be installed subsea onto existing architecture
• What types of operational issues can be solved through design of bespoke equipment

About the Presenter

Nick Pacewicz is General Manager of our Aberdeen office and has over 8 years of specialist engineering experience in the design and numerical analysis of shallow and deepwater riser systems, including drilling risers, jack-up systems, completion risers and conductor systems. He has notable experience in component design using 3D finite element analysis, including analysis of wellhead and conductor systems to determine fatigue damage in North Sea wells.